40 V 600 mA 1ch Constant Current Driver for Automotive LED ...
Constant Current Led Driver
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Transcript of Constant Current Led Driver
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F E A T U R E S D E S C R I P T I O N
A P P L I C A T I O N S
VIN
CTRL
SW
OVP
GND
L14.7 H
Rs
13
D1
Vin1.8 V to 6 V
FB
LED
RS
Enable/PWM Brightness Control100 Hz to 50 kHz
CO
100 nF
Cin4.7 F
3
5
6
4
8
7
1
2
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
C O N S T A N T C U R R E N T L E D D R I V E R
C u r r e n t S o u r c e W i t h O v e r v o l t a g e P r o t e c t i o n T h e T P S 6 1 0 4 2 i s a h i g h f r e q u e n c y b o o s t c o n v e r t e r w i t h c o n s t a n t c u r r e n t o u t p u t t h a t d r i v e s w h i t e L E D s I n p u t V o l t a g e R a n g e . . 1 . 8 V t o 6 V o r s i m i l a r . T h e L E D c u r r e n t i s s e t w i t h t h e e x t e r n a l I n t e r n a l 3 0 V S w i t c h s e n s e r e s i s t o r ( R S ) a n d i s d i r e c t l y r e g u l a t e d b y t h e
U p t o 8 5 % E f f i c i e n c y f e e d b a c k p i n ( F B ) t h a t r e g u l a t e s t h e v o l t a g e a c r o s s P r e c i s e B r i g h t n e s s C o n t r o l U s i n g P W M S i g n a l t h e s e n s e r e s i s t o r R S t o 2 5 2 m V ( t y p ) . T o c o n t r o l
L E D b r i g h t n e s s , t h e L E D c u r r e n t c a n b e p u l s e d b y o r A n a l o g S i g n a l a p p l y i n g a P W M ( p u l s e w i d t h m o d u l a t e d ) s i g n a l w i t h S w i t c h i n g F r e q u e n c y . . U p t o 1 M H z a f r e q u e n c y r a n g e o f 1 0 0 H z t o 5 0 k H z t o t h e c o n t r o l
I n t e r n a l P o w e r M O S F E T S w i t c h . . 5 0 0 m A p i n ( C T R L ) . T o a l l o w h i g h e r f l e x i b i l i t y , t h e d e v i c e c a n b e c o n f i g u r e d w h e r e t h e b r i g h t n e s s c a n b e c o n t r o l l e d O p e r a t e s W i t h S m a l l O u t p u t C a p a c i t o r s D o w n b y a n a n a l o g s i g n a l a s w e l l , a s d e s c r i b e d i n t h e t o 1 0 0 n F a p p l i c a t i o n i n f o r m a t i o n s e c t i o n . T o a v o i d p o s s i b l e
D i s c o n n e c t s L E D s D u r i n g S h u t d o w n l e a k a g e c u r r e n t s t h r o u g h t h e L E D s d u r i n g s h u t d o w n ,
N o L o a d Q u i e s c e n t C u r r e n t . . 3 8 A T y p t h e c o n t r o l p i n ( C T R L ) d i s a b l e s t h e d e v i c e a n d d i s c o n n e c t s t h e L E D s f r o m g r o u n d . F o r m a x i m u m S h u t d o w n C u r r e n t . . 0 . 1 A T y p s a f e t y d u r i n g o p e r a t i o n , t h e o u t p u t h a s i n t e g r a t e d A v a i l a b l e i n a S m a l l 3 m m 3 m m Q F N o v e r v o l t a g e p r o t e c t i o n t h a t p r e v e n t s d a m a g e t o t h e
P a c k a g e d e v i c e i n c a s e o f a h i g h i m p e d a n c e o u t p u t ( e . g . f a u l t y L E D ) .
W h i t e L E D S u p p l y f o r B a c k l i g h t / S i d e l i g h t D i s p l a y s
P D A , P o c k e t P C , S m a r t P h o n e s
H a n d h e l d D e v i c e s
C e l l u l a r P h o n e s
L a r g e r o u t p u t c a p a c i t o r v a l u e s l i k e 1 F a n d l a r g e r , r e d u c e t h e L E D r i p p l e c u r r e n t a n d i m p r o v e l i n e r e g u l a t i o n .
F i g u r e 1 . T y p i c a l A p p l i c a t i o n
P l e a s e b e a w a r e t h a t a n i m p o r t a n t n o t i c e c o n c e r n i n g a v a i l a b i l i t y , s t a n d a r d w a r r a n t y , a n d u s e i n c r i t i c a l a p p l i c a t i o n s o f T e x a s I n s t r u m e n t s s e m i c o n d u c t o r p r o d u c t s a n d d i s c l a i m e r s t h e r e t o a p p e a r s a t t h e e n d o f t h i s d a t a s h e e t .
P R O D U C T I O N D A T A i n f o r m a t i o n i s c u r r e n t a s o f p u b l i c a t i o n d a t e . C o p y r i g h t 2 0 0 2 2 0 0 7 , T e x a s I n s t r u m e n t s I n c o r p o r a t e d P r o d u c t s c o n f o r m t o s p e c i f i c a t i o n s p e r t h e t e r m s o f t h e T e x a s I n s t r u m e n t s s t a n d a r d w a r r a n t y . P r o d u c t i o n p r o c e s s i n g d o e s n o t
n e c e s s a r i l y i n c l u d e t e s t i n g o f a l l p a r a m e t e r s .
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A B S O L U T E M A X I M U M R A T I N G S
D I S S I P A T I O N R A T I N G
R E C O M M E N D E D O P E R A T I N G C O N D I T I O N S
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
O R D E R I N G I N F O R M A T I O N ( 1 )
T A P a c k a g e P a c k a g e M a r k i n g
4 0 t o 8 5 C T P S 6 1 0 4 2 D R B B H S
( 1 ) T h e D R B p a c k a g e i s a v a i l a b l e t a p e d a n d r e e l e d . A d d R s u f f i x ( T P S 6 1 0 4 2 D R B R ) t o o r d e r q u a n t i t i e s o f 3 0 0 0 d e v i c e s p e r r e e l . A d d T s u f f i x ( T P S 6 1 0 4 2 D R B T ) t o o r d e r q u a n t i t i e s o f 2 5 0 d e v i c e s p e r r e e l .
o v e r o p e r a t i n g f r e e - a i r t e m p e r a t u r e r a n g e ( u n l e s s o t h e r w i s e n o t e d ) ( 1 )
T P S 6 1 0 4 2
S u p p l y V o l t a g e s , v ( V I N ) ( 2 ) 0 . 3 V t o 7 V
V o l t a g e s , V ( R s ) , V ( C T R L ) , V ( F B ) 0 . 3 V t o V i n + 0 . 3 V
V o l t a g e s , V ( S W ) , V ( L E D ) ( 2 ) 3 0 V
V o l t a g e , V ( O V P ) 3 0 V
C o n t i n u o u s p o w e r d i s s i p a t i o n S e e D i s s i p a t i o n R a t i n g T a b l e
O p e r a t i n g j u n c t i o n t e m p e r a t u r e r a n g e 4 0 C t o 1 5 0 C
S t o r a g e t e m p e r a t u r e r a n g e , T S T G 6 5 C t o 1 5 0 C
L e a d t e m p e r a t u r e ( s o l d e r i n g , 1 0 s e c ) 2 6 0 C
( 1 ) S t r e s s e s b e y o n d t h o s e l i s t e d u n d e r a b s o l u t e m a x i m u m r a t i n g s m a y c a u s e p e r m a n e n t d a m a g e t o t h e d e v i c e . T h e s e a r e s t r e s s r a t i n g s o n l y , a n d f u n c t i o n a l o p e r a t i o n o f t h e d e v i c e a t t h e s e o r a n y o t h e r c o n d i t i o n s b e y o n d t h o s e i n d i c a t e d u n d e r r e c o m m e n d e d o p e r a t i n g c o n d i t i o n s i s n o t i m p l i e d . E x p o s u r e t o a b s o l u t e - m a x i m u m - r a t e d c o n d i t i o n s f o r e x t e n d e d p e r i o d s m a y a f f e c t d e v i c e r e l i a b i l i t y .
( 2 ) A l l v o l t a g e v a l u e s a r e w i t h r e s p e c t t o n e t w o r k g r o u n d t e r m i n a l .
P A C K A G E T A 2 5 C P O W E R D E R A T I N G F A C T O R T A = 7 0 C P O W E R T A = 8 5 C P O W E R R A T I N G A B O V E T A = 2 5 C R A T I N G R A T I N G
8 p i n Q F N ( 1 ) 3 7 0 m W 3 . 7 m W / C 2 0 4 m W 1 4 8 m W
( 1 ) T h e t h e r m a l r e s i s t a n c e j u n c t i o n t o a m b i e n t o f t h e 8 - p i n Q F N p a c k a g e i s 2 7 0 C / W . S t a n d a r d 2 - l a y e r P C B w i t h o u t v i a s f o r t h e t h e r m a l p a d . S e e t h e a p p l i c a t i o n s e c t i o n o n h o w t o i m p r o v e t h e t h e r m a l r e s i s t a n c e R J A .
M I N T Y P M A X U N I T
V I I n p u t v o l t a g e r a n g e 1 . 8 6 V
V s O u t p u t v o l t a g e r a n g e V I N 2 7 . 5 V
V S W S w i t c h v o l t a g e 3 0 V
I ( L E D ) M a x i m u m L E D s w i t c h c u r r e n t 6 0 m A
L I n d u c t o r ( 1 ) 4 . 7 H
f S w i t c h i n g f r e q u e n c y ( 1 ) 1 M H z
C I I n p u t c a p a c i t o r ( 1 ) 4 . 7 F
C O O u t p u t c a p a c i t o r ( 1 ) 1 0 0 n F
T A O p e r a t i n g a m b i e n t t e m p e r a t u r e 4 0 8 5 C
T J O p e r a t i n g j u n c t i o n t e m p e r a t u r e 4 0 1 2 5 C
( 1 ) S e e a p p l i c a t i o n s e c t i o n f o r f u r t h e r i n f o r m a t i o n
2 S u b m i t D o c u m e n t a t i o n F e e d b a c k
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E L E C T R I C A L C H A R A C T E R I S T I C S
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
VI = 3 . 6 V , C T R L = V I, TA = - 4 0 C t o + 8 5 C, t y p i c a l v a l u e s a r e a t T A = 2 5 C ( u n l e s s o t h e r w i s e n o t e d )
P A R A M E T E R T E S T C O N D I T I O N S M I N T Y P M A X U N I T
S u p p l y c u r r e n t
V I I n p u t v o l t a g e r a n g e 1 . 8 6 . 0 V
I( Q ) O p e r a t i n g q u i e s c e n t c u r r e n t i n t o V I N I O = 0 m A , n o t s w i t c h i n g 3 8 6 5 A I O ( s d ) S h u t d o w n c u r r e n t C T R L = G N D 0 . 1 1 A
V U V L O U n d e r - v o l t a g e l o c k o u t t h r e s h o l d V I f a l l i n g 1 . 5 1 . 7 V
C T R L
V I H C T R L h i g h l e v e l i n p u t v o l t a g e 1 . 3 V
V I L C T R L l o w l e v e l i n p u t v o l t a g e 0 . 3 V
II k g C T R L i n p u t l e a k a g e c u r r e n t C T R L = G N D o r V I N 0 . 1 A
to n M i n i m u m C T R L p u l s e w i d t h t o e n a b l e C T R L = l o w t o h i g h 5 0 u s
to f f M i n i m u m C T R L p u l s e w i d t h t o d i s a b l e C T R L = h i g h t o l o w 1 0 3 2 m s
f ( C T R L ) P W M s w i t c h i n g f r e q u e n c y a p p l i e d t o 0 . 1 5 0 k H z C T R L
D ( C T R L ) P W M d u t y c y c l e a p p l i e d t o C T R L 1 % 1 0 0 %
P o w e r s w i t c h a n d c u r r e n t l i m i t ( S W ) V S M a x i m u m s w i t c h v o l t a g e 3 0 V
r d s ( O N ) M O S F E T o n - r e s i s t a n c e V I = 3 . 6 V ; I ( S W ) = 2 0 0 m A 3 0 0 6 0 0 m
Il k g M O S F E T l e a k a g e c u r r e n t V ( S W ) = 2 8 V 0 . 1 1 0 A
IL I M M O F S E T c u r r e n t l i m i t 4 0 0 5 0 0 6 0 0 m A
L E D s w i t c h a n d c u r r e n t l i m i t ( L E D )
V S M a x i m u m s w i t c h v o l t a g e 3 0 V
r d s ( O N ) M O S F E T o n - r e s i s t a n c e V I = 3 . 6 V ; I S = 2 0 m A 1 2
Il k g M O S F E T l e a k a g e c u r r e n t V ( L E D ) = 2 8 V 0 . 1 1 0 A
O u t p u t
V O O u t p u t v o l t a g e r a n g e V I 2 7 . 5 V
I ( F B ) F e e d b a c k i n p u t b i a s c u r r e n t ( 1 ) V ( F B ) = 0 . 2 5 2 V 1 0 0 n A
V F B F e e d b a c k t r i p p o i n t v o l t a g e 1 . 8 V V I 6 V 2 4 4 2 5 2 2 6 0 m V
V ( O V P ) O u t p u t o v e r v o l t a g e p r o t e c t i o n V O r i s i n g 2 7 . 5 2 9 3 0 V
V h y s ( O V P ) O u t p u t o v e r v o l t a g e p r o t e c t i o n h y s t e r e s i s 5 7 V
I ( O V P ) O V P i n p u t c u r r e n t V O = 1 5 V 9 1 2 A
( 1 ) T h e f e e d b a c k i n p u t i s h i g h i m p e d a n c e M O S F E T G a t e i n p u t .
3S u b m i t D o c u m e n t a t i o n F e e d b a c k
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SW8
OVP7
GND6
CTRL5
LED
DRB PACKAGE
(TOP VIEW)
1
RS 2
VIN 3
FB 4
Exposed
ThermalDie Pad
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
T h e e x p o s e d t h e r m a l d i e p a d i s c o n n e c t e d t o G N D .
T e r m i n a l F u n c t i o n s
T E R M I N A L N A M E N O . I / O D E S C R I P T I O N
C o m b i n e d e n a b l e a n d P W M c o n t r o l p i n . I f C T R L i s c o n s t a n t l y p u l l e d h i g h , t h e d e v i c e i s e n a b l e d a n d t h e C T R L 5 I i n t e r n a l L E D s w i t c h ( Q 2 ) i s c o n s t a n t l y t u r n e d o n . W h e n C T R L i s p u l l e d t o G N D , t h e d e v i c e i s d i s a b l e d .
A p p l y a P W M s i g n a l ( 1 0 0 H z t o 5 0 k H z ) t o t h i s p i n t o c o n t r o l t h e b r i g h t n e s s o f t h e L E D s
F B 4 I F e e d b a c k . F B r e g u l a t e s t h e L E D c u r r e n t t h r o u g h t h e s e n s e r e s i s t o r b y r e g u l a t i n g t h e v o l t a g e a c r o s s R S t o2 5 2 m V .
G N D 6 G N D
L E D 1 I I n p u t o f t h e L E D s w i t c h ( Q 2 ) . C o n n e c t t h e L E D s t o t h i s p i n .
O V P 7 I O v e r v o l t a g e p r o t e c t i o n . O V P i s c o n n e c t e d t o t h e o u t p u t c a p a c i t o r o f t h e c o n v e r t e r .
R S 2 O O u t p u t o f t h e i n t e r n a l L E D s w i t c h . T h e s e n s e r e s i s t o r t h a t p r o g r a m s t h e L E D c u r r e n t i s c o n n e c t e d t o R S .
S W 8 I D r a i n o f t h e i n t e g r a t e d s w i t c h ( Q 1 )
V I N 3 I I n p u t s u p p l y p i n .
4 S u b m i t D o c u m e n t a t i o n F e e d b a c k
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UVLO
Bias
+
+
CTRL
EN
VREF
0.252 V
Thermal
Shutdown
Control
Logic
EN
Gate
Driver
VIN
OVP
SW
R1
2 M
R2
30 k
Current
LimitSoftstart
6 s Max
On Time
Overvoltage Protection
0.4 V
Enable
Control
Logic
EN
PWM
Gate
DriveGND
FB
Error
Comparator
VREF
400 ns Min
Off Time
Q1
Q2
LED
RS
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
F U N C T I O N A L B L O C K D I A G R A M
5S u b m i t D o c u m e n t a t i o n F e e d b a c k
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T Y P I C A L C H A R A C T E R I S T I C S
70
72
74
76
78
80
82
84
86
88
1 2 3 4 5 6
Efficiency%
4 LEDs 13 V, CO= 1 F
VI Input Voltage V
IO= 15 mA
70
72
74
76
78
80
82
84
86
88
90
0.1 1 10 100
IO Output Current mA
Efficiency%
4 LEDs 13 V, CO= 1 F
VI= 4.2V
VI= 3.6V
VI= 2.4V
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
T a b l e o f G r a p h s
F I G U R E
v s L E D c u r r e n t F i g u r e 2 E f f i c i e n c y
v s I n p u t v o l t a g e F i g u r e 3
IQ O p e r a t i n g Q u i e s c e n t C u r r e n t i n t o V I N v s I n p u t v o l t a g e a n d T e m p e r a t u r e F i g u r e 4
V ( F B ) F e e d b a c k v o l t a g e v s T e m p e r a t u r e F i g u r e 5
I ( F B ) F e e d b a c k c u r r e n t v s T e m p e r a t u r e F i g u r e 6
v s T e m p e r a t u r e F i g u r e 7 M a i n s w i t c h Q 1
v s I n p u t v o l t a g e F i g u r e 8 r d s ( o n )
v s T e m p e r a t u r e F i g u r e 9 L E D s w i t c h Q 2
v s I n p u t v o l t a g e F i g u r e 1 0
IL E D A v e r a g e L E D c u r r e n t v s P W M d u t y c y c l e o n C T R L p i n F i g u r e 1 1
S o f t s t a r t F i g u r e 1 2
P F M o p e r a t i o n ( f i x e d p e a k c u r r e n t c o n t r o l ) F i g u r e 1 3
B u r s t m o d e o p e r a t i o n ( f i x e d p e a k c u r r e n t F i g u r e 1 4 c o n t r o l )
P W M d i m m i n g F i g u r e 1 5
E f f i c i e n c y E f f i c i e n c y v s v s
L E D C u r r e n t I n p u t V o l t a g e
F i g u r e 2 . F i g u r e 3 .
6 S u b m i t D o c u m e n t a t i o n F e e d b a c k
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VI- Input Voltage - V
0
5
10
15
20
25
3035
40
45
50
1.8 2.4 3.0 3.6 4.2 4.8 5.4 6.0
QuiescentCurrentinto
VI/A
TA= 25C
TA= -40C
TA= 85C
TA- Free-Air Temperature - C
240
242
244
246
248
250
252254
256
258
260
-40 -15 10 35 60 85
V(fb)-FeedbackVoltag
e-mV VCC= 3.7 V
TA- Free-Air Temperature - C
-60
-40
-20
0
20
40
60
-40 -15 10 35 60 85
I(fb)-FeedbackCurrent-nA
VCC= 3.6 V
VCC= 2.4 VVCC= 5 V
200
250
300
350
400
450
500
40 15 10 35 60 85
TA Free-Air Temperature C
rds(on)
On-StateResistancem VCC= 3.6 V
0
100
200
300
400
500
600
1.8 2.4 3.0 3.6 4.2 4.8 5.4 6.0
VI Input Voltage V
rds(on)
On
-StateResistancem TA= 27C
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
-40 -15 10 35 60 85
TA- Free-Air Temperature - C
rds(on)-O
n-StateResistance- VCC= 3.6 V
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
O p e r a t i n g Q u i e s c e n t C u r r e n t i n t o V I N F e e d b a c k V o l t a g e v s v s
I n p u t V o l t a g e a n d T e m p e r a t u r e T e m p e r a t u r e
F i g u r e 4 . F i g u r e 5 .
F e e d b a c k C u r r e n t r d s ( o n ) M a i n S w i t c h ( Q 1 )
v s v s T e m p e r a t u r e T e m p e r a t u r e
F i g u r e 6 . F i g u r e 7 .
r d s ( O N ) M a i n S w i t c h ( Q 1 ) r d s ( o n ) L E D S w i t c h ( Q 2 ) v s v s
I n p u t V o l t a g e T e m p e r a t u r e
F i g u r e 8 . F i g u r e 9 .
7S u b m i t D o c u m e n t a t i o n F e e d b a c k
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0.0
0.5
1.0
1.5
2.0
2.5
3.0
1.8 2.4 3.0 3.6 4.2 4.8 5.4 6.0
VI- Input Voltage - V
rds(on)-On-StateResistance- TA= 25C
0
5
10
15
20
0 20 40 60 80 100
Duty Cycle - %
IO-
OutputCurrent-mA
fPWM= 100 Hz fPWM= 50 kHz
fPWM= 25 kHz
50s/Div
Vout10V/Div
CTRL
1V/Div
Input Current
100mA/Div
2.5s/Div
Vsw
5V/Div
LED Current
20mA/Div
Vout
500mV/Div
2.5s/Div
Vsw
5V/Div
LED Current
20mA/Div
Vout
50mV/Div
25s/Div
Vsw
5V/Div
LED Current
20mA/Div
Vout
500mV/Div
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
r d s ( o n ) L E D S w i t c h ( Q 2 ) A v e r a g e L E D C u r r e n t v s v s
I n p u t V o l t a g e P W M D u t y C y c l e o n C T R L P i n
F i g u r e 1 0 . F i g u r e 1 1 .
S o f t s t a r t P F M O p e r a t i o n
F i g u r e 1 2 . F i g u r e 1 3 .
B u s t M o d e O p e r a t i o n P W M D i m m i n g
F i g u r e 1 4 . F i g u r e 1 5 .
8 S u b m i t D o c u m e n t a t i o n F e e d b a c k
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D E T A I L E D D E S C R I P T I O N
O p e r a t i o n
B o o s t C o n v e r t e r
P e a k C u r r e n t C o n t r o l ( B o o s t C o n v e r t e r )
IP(typ)
I(LIM)
VI
L 100 ns
IP(typ)
500 mAV
IL 100 ns
S o f t s t a r t
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
T h e T P S 6 1 0 4 2 o p e r a t e s l i k e a s t a n d a r d b o o s t c o n v e r t e r b u t r e g u l a t e s t h e v o l t a g e a c r o s s t h e s e n s e r e s i s t o r ( R S )i n s t e a d o f t h e o u t p u t v o l t a g e . T h i s g i v e s a n a c c u r a t e r e g u l a t e d L E D c u r r e n t i n d e p e n d e n t o f t h e i n p u t v o l t a g e a n dn u m b e r o f L E D s c o n n e c t e d . W i t h i n t e g r a t e d o v e r v o l t a g e p r o t e c t i o n ( O V P ) t h e T P S 6 1 0 4 2 i s c o n f i g u r e d a s a c u r r e n t s o u r c e w i t h o v e r v o l t a g e p r o t e c t i o n i d e a l l y s u i t e d t o d r i v e L E D s . W i t h t h e 3 0 V i n t e r n a l s w i t c h , t h e d e v i c e c a n g e n e r a t e o u t p u t v o l t a g e s o f u p t o 2 7 . 5 V a n d h a s a n i n t e r n a l 5 0 0 m A M O S F E T s w i t c h ( Q 1 ) . T h i s a l l o w s s e v e r a l L E D s t o b e c o n n e c t e d i n s e r i e s t o t h e o u t p u t . T h e i n t e r n a l L E D s w i t c h ( Q 2 ) i n s e r i e s w i t h t h e L E D s h a s a m a x i m u m c u r r e n t r a t i n g o f 6 0 m A a n d d i s c o n n e c t s t h e L E D s f r o m g r o u n d d u r i n g s h u t d o w n . T h e L E D s w i t c h i s d r i v e n b y a P W M s i g n a l a p p l i e d t o t h e c o n t r o l p i n ( C T R L ) , w h i c h d i r e c t l y c o n t r o l s t h e L E D b r i g h t n e s s . W i t h t h i s c o n t r o l m e t h o d t h e L E D b r i g h t n e s s d e p e n d s o n t h e P W M d u t y c y c l e o n l y a n d i s i n d e p e n d e n t o f t h e P W M f r e q u e n c y a n d a m p l i t u d e .
T h e b o o s t c o n v e r t e r o p e r a t e s i n a p u l s e f r e q u e n c y m o d u l a t i o n ( P F M ) s c h e m e w i t h c o n s t a n t p e a k c u r r e n t c o n t r o l . T h i s c o n t r o l s c h e m e m a i n t a i n s h i g h e f f i c i e n c y o v e r t h e e n t i r e l o a d c u r r e n t r a n g e a n d w i t h a s w i t c h i n g f r e q u e n c y o f u p t o 1 M H z , e n a b l e s t h e u s e o f s m a l l e x t e r n a l c o m p o n e n t s . T h e c o n v e r t e r m o n i t o r s t h e s e n s e v o l t a g e a c r o s s R S w i t h t h e f e e d b a c k p i n ( F B ) a n d , w h e n t h e f e e d b a c k v o l t a g e f a l l s b e l o w t h e r e f e r e n c e v o l t a g e ( 2 5 2 m V t y p ) ,
t h e m a i n s w i t c h t u r n s o n a n d t h e c u r r e n t r a m p s u p . T h e m a i n s w i t c h t u r n s o f f w h e n t h e i n d u c t o r c u r r e n t r e a c h e s t h e i n t e r n a l l y s e t p e a k c u r r e n t o f 5 0 0 m A ( t y p ) . R e f e r t o t h e p e a k c u r r e n t c o n t r o l s e c t i o n f o r m o r e i n f o r m a t i o n . T h e s e c o n d c r i t e r i a t h a t t u r n s o f f t h e m a i n s w i t c h i s t h e m a x i m u m o n - t i m e o f 6 s ( t y p ) . T h i s l i m i t s t h e m a x i m u m o n - t i m e o f t h e c o n v e r t e r i n e x t r e m e c o n d i t i o n s . A s t h e s w i t c h i s t u r n e d o f f t h e e x t e r n a l S c h o t t k y d i o d e i s f o r w a r d b i a s e d , d e l i v e r i n g t h e s t o r e d i n d u c t o r e n e r g y t o t h e o u t p u t . T h e m a i n s w i t c h r e m a i n s o f f u n t i l t h e m i n i m u m o f f t i m e o f 4 0 0 n s ( t y p ) h a s p a s s e d a n d t h e f e e d b a c k v o l t a g e i s b e l o w t h e r e f e r e n c e v o l t a g e a g a i n . U s i n g t h i s P F M p e a k c u r r e n t c o n t r o l s c h e m e , t h e c o n v e r t e r o p e r a t e s i n d i s c o n t i n u o u s c o n d u c t i o n m o d e ( D C M ) w h e r e t h e s w i t c h i n g f r e q u e n c y d e p e n d s o n t h e i n d u c t o r , i n p u t a n d o u t p u t v o l t a g e , a n d L E D c u r r e n t . L o w e r L E D c u r r e n t s r e d u c e t h e s w i t c h i n g f r e q u e n c y , w h i c h r e s u l t s i n h i g h e f f i c i e n c y o v e r t h e e n t i r e L E D c u r r e n t r a n g e . T h i s r e g u l a t i o n s c h e m e i s i n h e r e n t l y s t a b l e , a l l o w i n g a w i d e r a n g e f o r t h e s e l e c t i o n o f t h e i n d u c t o r a n d o u t p u t c a p a c i t o r .
T h e i n t e r n a l s w i t c h i s t u r n e d o n u n t i l t h e i n d u c t o r c u r r e n t r e a c h e s t h e D C c u r r e n t l i m i t ( I L I M ) o f 5 0 0 m A ( t y p ) . D u e t o t h e i n t e r n a l c u r r e n t l i m i t d e l a y o f 1 0 0 n s ( t y p ) t h e a c t u a l c u r r e n t e x c e e d s t h e D C c u r r e n t l i m i t t h r e s h o l d b y a s m a l l a m o u n t . T h e t y p i c a l p e a k c u r r e n t l i m i t c a n b e c a l c u l a t e d :
T h e h i g h e r t h e i n p u t v o l t a g e a n d t h e l o w e r t h e i n d u c t o r v a l u e , t h e g r e a t e r t h e c u r r e n t l i m i t o v e r s h o o t .
A l l i n d u c t i v e s t e p - u p c o n v e r t e r s e x h i b i t h i g h i n - r u s h c u r r e n t d u r i n g s t a r t - u p i f n o s p e c i a l p r e c a u t i o n s a r e t a k e n .
T h i s c a n c a u s e v o l t a g e d r o p s a t t h e i n p u t r a i l d u r i n g s t a r t - u p , w h i c h m a y r e s u l t i n a n u n w a n t e d o r p r e m a t u r e s y s t e m s h u t d o w n .
T h e T P S 6 1 0 4 2 l i m i t s t h i s i n - r u s h c u r r e n t d u r i n g s t a r t - u p b y i n c r e a s i n g t h e c u r r e n t l i m i t i n t w o s t e p s s t a r t i n g f r o m IL I M / 4 f o r 2 5 6 s w i t c h c y c l e s t o I L I M / 2 f o r t h e n e x t 2 5 6 s w i t c h c y c l e s a n d t h e n f u l l c u r r e n t l i m i t . S e e F i g u r e 1 2 f o rt y p i c a l s t a r t - u p b e h a v i o r .
9S u b m i t D o c u m e n t a t i o n F e e d b a c k
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C o n t r o l ( C T R L )
t
ton
Low
High
tp
D = tp/t
ton
toff
Minimum
On-Time
to Enable
the Device
(50 s)
Minimum
Off-Time
to Disable
the Device
(32 ms)
A p p l y i n g a P W M S i g n a l t o t h e C T R L P i n w i t h a n O n - T i m e t p 2 . 5 s
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
D E T A I L E D D E S C R I P T I O N ( c o n t i n u e d )
T h e C T R L p i n s e r v e s t w o f u n c t i o n s . O n e i s t h e e n a b l e a n d d i s a b l e o f t h e d e v i c e . T h e o t h e r i s t h e P W M c o n t r o l o f t h e i n t e r n a l L E D s w i t c h ( Q 2 ) . I f n o P W M s i g n a l i s a p p l i e d t o t h e C T R L p i n , t h e n t h e C T R L p i n c a n b e u s e d a s a s t a n d a r d e n a b l e p i n f o r t h e d e v i c e . T o e n a b l e t h e d e v i c e , t h e C T R L p i n m u s t b e p u l l e d h i g h f o r t i m e p e r i o d o f
a t l e a s t 5 0 s . T h e d e v i c e s t a r t s w i t h t h e S o f t s t a r t c y c l e . P u l l i n g t h e C T R L p i n t o G N D f o r a t i m e p e r i o d 3 2 m s d i s a b l e s t h e d e v i c e , d i s c o n n e c t i n g t h e L E D s f r o m G N D b y o p e n i n g t h e L E D s w i t c h ( Q 2 ) t o a v o i d a n y L E D l e a k a g e c u r r e n t . S e e F i g u r e 1 6 f o r t h e C T R L p i n t i m i n g .
T h e i n t e r n a l L E D s w i t c h ( Q 2 ) i s d r i v e n b y t h e P W M s i g n a l w h e n a p p l i e d t o t h e C T R L p i n . A p p l y i n g a P W M s i g n a l i n t h e r a n g e o f 1 0 0 H z t o 5 0 k H z a l l o w s t h e L E D c u r r e n t t o b e p u l s e d w i t h t h e d u t y c y c l e o f t h e P W M s i g n a l . T h e C T R L p i n a c c e p t s a P W M d u t y c y c l e f r o m D = 1 % t o 1 0 0 % . D u t y c y c l e s b e l o w 1 % a r e a l s o p o s s i b l e w i t h t h e r e s t r i c t i o n t h a t t h e d e v i c e i s f o r c e d i n t o s h u t d o w n a s t h e o f f t i m e o f t h e a p p l i e d P W M s i g n a l e x c e e d s 1 0 m s .
W h e n a P W M s i g n a l i s a p p l i e d t o t h e C T R L p i n t h e L E D s w i t c h ( Q 2 ) t u r n s o n i m m e d i a t e l y . T h e i n t e r n a l e r r o r c o m p a r a t o r i s d i s a b l e d f o r 4 0 0 n s . T h i s 4 0 0 n s d e l a y t i m e i s r e q u i r e d t o e s t a b l i s h t h e c o r r e c t v o l t a g e l e v e l a c r o s s t h e s e n s e r e s i s t o r R S a f t e r t h e L E D s w i t c h ( Q 2 ) i s c l o s e d .
T o a c h i e v e g o o d L E D c u r r e n t a c c u r a c y a n d l i n e a r i t y , t h e s w i t c h i n g f r e q u e n c y o f t h e c o n v e r t e r m u s t b e h i g h e r t h a n t h e P W M f r e q u e n c y a p p l i e d t o t h e C T R L p i n .
F i g u r e 1 6 . C T R L T i m i n g D i a g r a m
T h e C T R L t i m i n g d i a g r a m i s s h o w n i n F i g u r e 1 6 . T o e n a b l e t h e d e v i c e , t h e C T R L s i g n a l m u s t b e h i g h f o r 5 0 s . T h e P W M s i g n a l c a n t h e n b e a p p l i e d w i t h a p u l s e w i d t h ( t p ) g r e a t e r o r s m a l l e r t h a n t O N . T o f o r c e t h e d e v i c e i n t o s h u t d o w n m o d e , t h e C T R L s i g n a l m u s t b e l o w f o r a t l e a s t 3 2 m s . R e q u i r i n g t h e C T R L p i n t o b e l o w f o r 3 2 m S b e f o r e t h e d e v i c e e n t e r s s h u t d o w n a l l o w s f o r P W M d i m m i n g f r e q u e n c i e s a s l o w a s 1 0 0 H z . T h e d e v i c e i s e n a b l e d a g a i n w h e n a C T R L s i g n a l i s h i g h f o r a p e r i o d o f 5 0 s m i n i m u m . S e e F i g u r e 1 1 f o r t h e P W M d u t y c y c l e v e r s u s L E D c u r r e n t c h a r a c t e r i s t i c .
T h i s C T R L p i n m u s t b e t e r m i n a t e d .
I n s u c h a c a s e t h e o n - t i m e o f t h e P W M s i g n a l , t p , m u s t b e > 2 . 5 s u n t i l t h e s o f t s t a r t i s c o m p l e t e d . T h e s o f t s t a r t i s c o m p l e t e d a f t e r 5 1 2 s w i t c h i n g c y c l e s . T o s i m p l y , e s t i m a t e t h e s o f t s t a r t t i m e , m u l t i p l y t h e p e r i o d o f t h e P W M s i g n a l t i m e s 5 1 2 , a n d a d d 5 0 s t o i t . F o r a 5 0 - k H z s i g n a l t h i s w o u l d b e 1 0 . 3 m s a s a m i n i m u m s o f t s t a r t t i m e p e r i o d . A f t e r t h e s o f t s t a r t t i m e i s c o m p l e t e d t h e P W M o n t i m e c a n b e r e d u c e d t o t p > 4 0 0 n s .
1 0 S u b m i t D o c u m e n t a t i o n F e e d b a c k
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O v e r v o l t a g e P r o t e c t i o n ( O V P )
U n d e r v o l t a g e L o c k o u t
T h e r m a l S h u t d o w n
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
D E T A I L E D D E S C R I P T I O N ( c o n t i n u e d )
A s w i t h a n y c u r r e n t s o u r c e , t h e o u t p u t v o l t a g e r i s e s a s t h e o u t p u t i m p e d a n c e i n c r e a s e s o r i s d i s c o n n e c t e d . T o p r e v e n t t h e o u t p u t v o l t a g e f r o m e x c e e d i n g t h e m a x i m u m m a i n s w i t c h ( Q 1 ) v o l t a g e r a t i n g o f 3 0 V , a n o v e r v o l t a g e p r o t e c t i o n c i r c u i t i s i n t e g r a t e d . W h e n t h e o u t p u t v o l t a g e e x c e e d s t h e O V P t h r e s h o l d v o l t a g e , ( Q 1 ) t u r n s o f f . T h e
c o n v e r t e r s w i t c h r e m a i n s o f f u n t i l t h e o u t p u t v o l t a g e f a l l s b e l o w t h e O V P t h r e s h o l d v o l t a g e . A s l o n g a s t h e o u t p u t v o l t a g e i s b e l o w t h e O V P t h r e s h o l d t h e c o n v e r t e r c o n t i n u e s i t s n o r m a l o p e r a t i o n , u n t i l t h e o u t p u t v o l t a g e e x c e e d s t h e O V P t h r e s h o l d a g a i n .
A n u n d e r v o l t a g e l o c k o u t f e a t u r e p r e v e n t s m i s - o p e r a t i o n o f t h e d e v i c e a t i n p u t v o l t a g e s b e l o w 1 . 5 V ( t y p ) . A s l o n g a s t h e i n p u t v o l t a g e i s b e l o w t h e u n d e r v o l t a g e t h r e s h o l d t h e d e v i c e r e m a i n s o f f , w i t h t h e m a i n M O S F E T s w i t c h ( Q 1 ) a n d t h e L E D s w i t c h ( Q 2 ) o p e n .
A n i n t e r n a l t h e r m a l s h u t d o w n i s i m p l e m e n t e d i n t h e T P S 6 1 0 4 2 t h a t s h u t s d o w n t h e d e v i c e i f t h e t y p i c a l j u n c t i o n t e m p e r a t u r e o f 1 6 0 C i s e x c e e d e d . I f t h e d e v i c e i s i n t h e r m a l s h u t d o w n m o d e , t h e m a i n M O S F E T s w i t c h ( Q 1 ) a n d t h e L E D s w i t c h ( Q 2 ) a r e o p e n .
1 1S u b m i t D o c u m e n t a t i o n F e e d b a c k
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A P P L I C A T I O N I N F O R M A T I O N
I n d u c t o r S e l e c t i o n , M a x i m u m L o a d C u r r e n t , a n d S w i t c h i n g F r e q u e n c y
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Iload max
ip Vin
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Iload max
ip2 L Vin
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ip 500 mAVin
L 100 ns
fs(ILOAD)
2 ILOAD
VO V
I V
F
I(LIM)
VinL 100 ns
2
L
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
T h e P F M p e a k c u r r e n t c o n t r o l s c h e m e o f t h e T P S 6 1 0 4 2 i s i n h e r e n t l y s t a b l e . T h e i n d u c t o r v a l u e d o e s n o t a f f e c t t h e s t a b i l i t y o f t h e r e g u l a t o r . T h e s e l e c t i o n o f t h e i n d u c t o r t o g e t h e r w i t h t h e n o m i n a l L E D c u r r e n t , i n p u t , a n d o u t p u t v o l t a g e o f t h e a p p l i c a t i o n d e t e r m i n e s t h e s w i t c h i n g f r e q u e n c y o f t h e c o n v e r t e r .
T h e f i r s t s t e p i s t o c a l c u l a t e t h e m a x i m u m l o a d c u r r e n t t h e c o n v e r t e r c a n s u p p o r t u s i n g t h e s e l e c t e d i n d u c t o r . T h e i n d u c t o r v a l u e h a s l e s s e f f e c t o n t h e m a x i m u m a v a i l a b l e l o a d c u r r e n t a n d i s o n l y o f s e c o n d a r y o r d e r . A g o o d i n d u c t o r v a l u e t o s t a r t w i t h i s 4 . 7 H . D e p e n d i n g o n t h e a p p l i c a t i o n , i n d u c t o r v a l u e s d o w n t o 1 . 0 H c a n b e u s e d . T h e m a x i m u m i n d u c t o r v a l u e i s d e t e r m i n e d b y t h e m a x i m u m o n t i m e o f t h e s w i t c h o f 6 s ( t y p ) . T h e p e a k c u r r e n t l i m i t o f 5 0 0 m A ( t y p ) m u s t b e r e a c h e d w i t h i n t h i s 6 s f o r p r o p e r o p e r a t i o n . T h e m a x i m u m l o a d c u r r e n t o f t h e c o n v e r t e r i s d e t e r m i n e d a t t h e o p e r a t i o n p o i n t w h e r e t h e c o n v e r t e r s t a r t s t o e n t e r t h e c o n t i n u o u s c o n d u c t i o n m o d e . T h e c o n v e r t e r m u s t a l w a y s o p e r a t e i n d i s c o n t i n u o u s c o n d u c t i o n m o d e t o m a i n t a i n r e g u l a t i o n .
D e p e n d i n g o n t h e t i m e p e r i o d o f t h e i n d u c t o r c u r r e n t f a l l t i m e b e i n g l a r g e r o r s m a l l e r c o m p a r e d t o t h e m i n i m u m o f f t i m e o f t h e c o n v e r t e r ( 4 0 0 n s t y p ) , t h e m a x i m u m l o a d c u r r e n t c a n b e c a l c u l a t e d .
I n d u c t o r f a l l t i m e :
F o r t f a l l 4 0 0 n s
f o r t f a l l 4 0 0 n s
w i t h :
L = s e l e c t e d i n d u c t o r v a l u e
= e x p e c t e d c o n v e r t e r e f f i c i e n c y . T y p i c a l l y b e t w e e n 7 0 % t o 8 5 %
( P e a k i n d u c t o r c u r r e n t a s d e s c r i b e d i n t h e p e a k c u r r e n t c o n t r o l s e c t i o n )
T h e a b o v e f o r m u l a c o n t a i n s t h e e x p e c t e d c o n v e r t e r e f f i c i e n c y t h a t a l l o w s c a l c u l a t i n g t h e e x p e c t e d m a x i m u m l o a d c u r r e n t t h e c o n v e r t e r c a n s u p p o r t . T h e e f f i c i e n c y c a n b e t a k e n o u t o f t h e e f f i c i e n c y g r a p h s s h o w n i n F i g u r e 2 a n d F i g u r e 3 o r 8 0 % c a n b e u s e d a s a n a c c u r a t e e s t i m a t i o n .
I f t h e c o n v e r t e r c a n s u p p o r t t h e d e s i r e d L E D c u r r e n t , t h e n e x t s t e p i s t o c a l c u l a t e t h e c o n v e r t e r s w i t c h i n g f r e q u e n c y a t t h e o p e r a t i o n p o i n t , w h i c h m u s t b e 1 M H z . A l s o t h e c o n v e r t e r s w i t c h i n g f r e q u e n c y s h o u l d b e m u c h h i g h e r t h a n t h e a p p l i e d P W M f r e q u e n c y a t t h e C T R L p i n t o a v o i d n o n - l i n e a r b r i g h t n e s s c o n t r o l . A s s u m i n g t h e c o n v e r t e r s h o w s n o d o u b l e p u l s e s o r p u l s e b u r s t s ( F i g u r e 1 3 , F i g u r e 1 4 ) o n t h e s w i t c h n o d e ( S W ) t h e s w i t c h i n g f r e q u e n c y a t t h e o p e r a t i o n p o i n t c a n b e c a l c u l a t e d a s :
w i t h :
I ( L I M ) = m i n i m u m s w i t c h c u r r e n t l i m i t ( 5 0 0 m A t y p )
L = s e l e c t e d i n d u c t o r v a l u e
I ( L O A D ) = n o m i n a l l o a d o r L E D c u r r e n t
V F = R e c t i f i e r d i o d e f o r w a r d v o l t a g e ( t y p i c a l l y 0 . 3 V )
1 2 S u b m i t D o c u m e n t a t i o n F e e d b a c k
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13/27
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O u t p u t C a p a c i t o r S e l e c t i o n a n d L i n e R e g u l a t i o n
VO
IO
CO
1
fs(ILOAD)
I
(LIM) Vin
L 100 ns L
VO V
F V
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I
PESR
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
A P P L I C A T I O N I N F O R M A T I O N ( c o n t i n u e d )
T h e s m a l l e r t h e i n d u c t o r v a l u e , t h e h i g h e r t h e s w i t c h i n g f r e q u e n c y o f t h e c o n v e r t e r b u t t h e l o w e r t h e e f f i c i e n c y .
T h e s e l e c t e d i n d u c t o r m u s t h a v e a s a t u r a t i o n c u r r e n t t h a t m e e t s t h e m a x i m u m p e a k c u r r e n t o f t h e c o n v e r t e r a s c a l c u l a t e d i n t h e p e a k c u r r e n t c o n t r o l s e c t i o n . U s e t h e m a x i m u m v a l u e f o r I ( L I M ) ( 6 0 0 m A ) f o r t h i s c a l c u l a t i o n .
A n o t h e r i m p o r t a n t i n d u c t o r p a r a m e t e r i s t h e D C r e s i s t a n c e . T h e l o w e r t h e D C r e s i s t a n c e t h e h i g h e r t h e
e f f i c i e n c y o f t h e c o n v e r t e r . S e e T a b l e 1 a n d F i g u r e 2 2 t o F i g u r e 2 7 f o r i n d u c t o r s e l e c t i o n .
T a b l e 1 . P o s s i b l e I n d u c t o r
I n d u c t o r V a l u e C o m p o n e n t S u p p l i e r S i z e
1 0 H m u R a t a L Q H 4 3 C N 1 0 0 K 0 1 4 , 5 m m 3 , 2 m m 2 . 6 m m
4 . 7 H m u R a t a L Q H 3 2 C N 4 R 7 M 1 1 3 , 2 m m 2 , 5 m m 2 , 0 m m
1 0 H C o i l c r a f t D O 1 6 0 5 T - 1 0 3 M X 5 , 5 m m 4 , 1 m m 1 , 8 m m
4 . 7 H S u m i d a C D R H 3 D 1 6 - 4 R 7 3 , 8 m m 3 , 8 m m 1 , 8 m m
3 . 3 H S u m i d a C M D 4 D 1 1 - 3 R 3 3 , 5 m m 5 , 3 m m 1 , 2 m m
4 . 7 H S u m i d a C M D 4 D 1 1 - 4 R 7 3 , 5 m m 5 , 3 m m 1 , 2 m m
3 . 3 H S u m i d a C M D 4 D 1 1 - 3 R 3 3 , 5 m m 5 , 3 m m 1 , 2 m m
4 . 7 H C o i l t r o n i c s S D 1 2 - 4 R 7 5 , 2 m m 5 , 2 m m 1 , 2 m m
3 . 3 H C o i l c r a f t L P O 1 7 0 4 - 3 3 2 M 6 , 6 m m 5 , 5 m m 1 , 0 m m
4 . 7 H C o i l c r a f t L P O 1 7 0 4 - 4 7 2 M 6 , 6 m m 5 , 5 m m 1 , 0 m m
F o r b e t t e r o u t p u t v o l t a g e f i l t e r i n g , a l o w E S R o u t p u t c a p a c i t o r i s r e c o m m e n d e d . C e r a m i c c a p a c i t o r s h a v e a l o w E S R v a l u e , b u t d e p e n d i n g o n t h e a p p l i c a t i o n , t a n t a l u m c a p a c i t o r s c a n b e u s e d .
T h e s e l e c t i o n o f t h e o u t p u t c a p a c i t o r v a l u e d i r e c t l y i n f l u e n c e s t h e o u t p u t v o l t a g e r i p p l e o f t h e c o n v e r t e r w h i c h a l s o i n f l u e n c e s l i n e r e g u l a t i o n . T h e l a r g e r t h e o u t p u t v o l t a g e r i p p l e , t h e l a r g e r t h e l i n e r e g u l a t i o n , w h i c h m e a n s t h a t t h e L E D c u r r e n t c h a n g e s i f t h e i n p u t v o l t a g e c h a n g e s . I f a c e r t a i n c h a n g e i n L E D c u r r e n t g i v e s a n o t i c e a b l e c h a n g e i n L E D b r i g h t n e s s , d e p e n d s o n t h e L E D m a n u f a c t u r e r a n d o n t h e a p p l i c a t i o n . A p p l i c a t i o n s r e q u i r i n g g o o d l i n e r e g u l a t i o n 1 % / V ( t y p ) m u s t u s e o u t p u t c a p a c i t o r v a l u e s 1 F .
S e e T a b l e 2 a n d F i g u r e 2 2 t o F i g u r e 2 7 f o r t h e s e l e c t i o n o f t h e o u t p u t c a p a c i t o r . A s s u m i n g t h e c o n v e r t e r d o e s n o t s h o w d o u b l e p u l s e s o r p u l s e b u r s t s o n t h e s w i t c h n o d e ( S W ) , t h e o u t p u t v o l t a g e r i p p l e i s c a l c u l a t e d a s ( s e e F i g u r e 1 3 , F i g u r e 1 4 ) :
w i t h :
I ( L I M ) = m i n i m u m s w i t c h c u r r e n t l i m i t ( 4 0 0 m A t y p )
L = s e l e c t e d i n d u c t o r v a l u e
I ( L O A D ) = n o m i n a l l o a d c u r r e n t
fS = s w i t c h i n g f r e q u e n c y a t t h e n o m i n a l l o a d c u r r e n t a s c a l c u l a t e d b e f o r e .
V F = r e c t i f i e r d i o d e f o r w a r d v o l t a g e ( 0 . 3 V t y p )
C O = s e l e c t e d o u t p u t c a p a c i t o r
E S R = o u t p u t c a p a c i t o r E S R v a l u e
1 3S u b m i t D o c u m e n t a t i o n F e e d b a c k
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I n p u t C a p a c i t o r S e l e c t i o n
D i o d e S e l e c t i o n
E f f i c i e n c y
VLED
ILED
VI I
I
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
F o r g o o d i n p u t v o l t a g e f i l t e r i n g , l o w E S R c e r a m i c c a p a c i t o r s a r e r e c o m m e n d e d . A 4 . 7 F c e r a m i c i n p u t c a p a c i t o r i s s u f f i c i e n t f o r m o s t a p p l i c a t i o n s . F o r b e t t e r i n p u t v o l t a g e f i l t e r i n g t h e c a p a c i t o r v a l u e c a n b e i n c r e a s e d . R e f e r t o T a b l e 2 a n d F i g u r e 2 2 t o F i g u r e 2 7 f o r i n p u t c a p a c i t o r s e l e c t i o n .
T a b l e 2 . P o s s i b l e I n p u t a n d O u t p u t C a p a c i t o r s
C a p a c i t o r V o l t a g e r a t i n g C o m p o n e n t S u p p l i e r C o m m e n t s
4 . 7 F / X 5 R / 0 8 0 5 6 . 3 V T a y o Y u d e n J M K 2 1 2 B Y 4 7 5 M G C I
1 0 F / X 5 R / 0 8 0 5 6 . 3 V T a y o Y u d e n J M K 2 1 2 B J 1 0 6 M G C I
1 0 0 n F A n y C O
2 2 0 n F A n y C O
4 7 0 n F A n y C O
1 . 0 F / X 7 R / 1 2 0 6 2 5 V T a y o Y u d e n T M K 3 1 6 B J 1 0 5 K L C O
1 . 0 F / X 7 R / 1 2 0 6 3 5 V T a y o Y u d e n G M K 3 1 6 B J 1 0 5 K L C O
4 . 7 F / X 5 R / 1 2 1 0 2 5 V T a y o Y u d e n T M K 3 2 5 B J 4 7 5 M G C O
T o a c h i e v e h i g h e f f i c i e n c y , a S c h o t t k y d i o d e m u s t b e u s e d . T h e c u r r e n t r a t i n g o f t h e d i o d e m u s t m e e t t h e p e a k c u r r e n t r a t i n g o f t h e c o n v e r t e r a s i t i s c a l c u l a t e d i n t h e p e a k c u r r e n t c o n t r o l s e c t i o n . U s e t h e m a x i m u m v a l u e f o r I ( L i m ) f o r t h i s c a l c u l a t i o n . S e e T a b l e 3 a n d F i g u r e 2 2 t o F i g u r e 2 7 f o r t h e S c h o t t k y d i o d e s e l e c t i o n .
T a b l e 3 . P o s s i b l e D i o d e s
C o m p o n e n t S u p p l i e r R e v e r s e v o l t a g e
O N S e m i c o n d u c t o r M B R 0 5 3 0 3 0 V
O N S e m i c o n d u c t o r M B R 0 5 2 0 2 0 V
T o s h i b a C R S 0 2 3 0 V
Z e t e x Z H C S 4 0 0 4 0 V
T h e o v e r a l l e f f i c i e n c y o f t h e a p p l i c a t i o n d e p e n d s o n t h e s p e c i f i c a p p l i c a t i o n c o n d i t i o n s a n d m a i n l y o n t h e s e l e c t i o n o f t h e i n d u c t o r . A l o w e r i n d u c t o r v a l u e i n c r e a s e s t h e s w i t c h i n g f r e q u e n c y a n d s w i t c h i n g l o s s e s y i e l d i n g i n a l o w e r e f f i c i e n c y . A l o w e r i n d u c t o r d c r e s i s t a n c e h a s l o w e r c o p p e r l o s s e s , g i v i n g a h i g h e r e f f i c i e n c y . T h e r e f o r e , t h e e f f i c i e n c y c a n t y p i c a l l y v a r y 5 % d e p e n d i n g o n t h e s e l e c t e d i n d u c t o r . F i g u r e 2 a n d F i g u r e 3 c a nb e u s e d a s a g u i d e l i n e f o r t h e a p p l i c a t i o n e f f i c i e n c y . T h e s e c u r v e s s h o w t h e t y p i c a l e f f i c i e n c y p o w e r i n g f o u r L E D s u s i n g a 4 . 7 H i n d u c t o r w i t h j u s t 1 , 2 m m h e i g h t . T h e e f f i c i e n c y c u r v e i n F i g u r e 2 a n d F i g u r e 3 s h o w t h e e f f i c i e n c y d e l i v e r i n g t h e p o w e r t o t h e L E D s r a t h e r t h a n t h e o v e r a l l c o n v e r t e r e f f i c i e n c y a n d i s c a l c u l a t e d a s :
1 4 S u b m i t D o c u m e n t a t i o n F e e d b a c k
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S e t t i n g T h e L E D C u r r e n t
VIN
CTRL
SW
OVP
GND
Rs
FB
LED
RS
PWM
100 Hz to 50 kHz
ILED
VFB
RS
0.252 V
RS
R2
PWM
Signal
C
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Optional Filter for theuse of a PWM Signal
VADJ(Brightness Control)
VIN
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Enable: CTRL = High
Disable: CTRL = Low
R1
I1
Vs
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
T h e c o n v e r t e r r e g u l a t e s t h e L E D c u r r e n t b y r e g u l a t i n g t h e v o l t a g e a c r o s s t h e c u r r e n t s e n s e r e s i s t o r ( R S ) . T h e v o l t a g e a c r o s s t h e s e n s e r e s i s t o r i s r e g u l a t e d t o t h e i n t e r n a l r e f e r e n c e v o l t a g e o f V ( F B ) = 2 5 2 m V .
F i g u r e 1 7 . S e t t i n g t h e L E D C u r r e n t
T h e L E D c u r r e n t c a n b e c a l c u l a t e d :
T h e c u r r e n t p r o g r a m m i n g m e t h o d i s u s e d w h e n t h e b r i g h t n e s s o f t h e L E D s i s f i x e d o r c o n t r o l l e d b y a P W M s i g n a l a p p l i e d t o t h e C T R L p i n . W h e n u s i n g a P W M s i g n a l o n t h e C T R L p i n , t h e L E D b r i g h t n e s s i s o n l y d e p e n d e n t o n t h e P W M d u t y c y c l e , i n d e p e n d e n t o f t h e P W M f r e q u e n c y , o r a m p l i t u d e , w h i c h s i m p l i f i e s t h e s y s t e m .
A l t e r n a t i v e l y , a n a n a l o g v o l t a g e c a n b e u s e d a s w e l l t o c o n t r o l t h e L E D b r i g h t n e s s .
F i g u r e 1 8 . S e t t i n g t h e L E D C u r r e n t
1 5S u b m i t D o c u m e n t a t i o n F e e d b a c k
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R2Vref V
adj(min)
I1
R1 Vref
IO(max)
R2 Vadj(min)
IO(min)
R2 Vadj(max)
Vadj(max)
IO(max)
Vref I
O(min) V
adj(min) I
O(min) V
ref I
O(max)
VS V
ref 1R1
R2R1
R2 V
adj(min)
RS
VS
IO(max)
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
I n F i g u r e 1 8 t h e L E D c u r r e n t i s d e t e r m i n e d b y t h e v o l t a g e a p p l i e d t o R 2 ( V ( a d j ) ) a n d t h e s e l e c t i o n o f R 1 , R 2 a n d t h e s e n s e r e s i s t o r ( R S ) . I n t h i s c o n f i g u r a t i o n , t h e L E D c u r r e n t i s l i n e a r c o n t r o l l e d i n s t e a d o f p u l s e d a s i n t h e c o n f i g u r a t i o n b e f o r e . T o s e l e c t t h e r e s i s t o r v a l u e s f o l l o w i n g s t e p s a r e r e q u i r e d .
1 . S e l e c t t h e v o l t a g e V ( a d j m a x ) t o t u r n t h e L E D s o f f . V( a d j m a x ) ( e . g . 3 . 3 V )
2 . S e l e c t t h e v o l t a g e V ( a d j m i n ) t o t u r n t h e L E D s f u l l y o n . V( a d j m i n ) ( e . g . 0 . 0 V )
3 . S e l e c t t h e m a x i m u m a n d m i n i m u m L E D c u r r e n t I O ( m a x ) a n d I O ( m i n ) . ( e . g . I O ( m a x ) = 2 0 m A , I O ( m i n ) = 0 m A )
4 . C a l c u l a t e R 2 t o a c h i e v e a f e e d b a c k c u r r e n t i n t h e r a n g e o f I 1 = 3 A t o 1 0 A a s t h e L E D s a r e f u l l y t u r n e d o n :
5 . C a l c u l a t i o n o f R 1
6 . C a l c u l a t i o n o f t h e s e n s e v o l t a g e ( V S ) a t m a x i m u m L E D c u r r e n t
7 . C a l c u l a t i o n o f t h e r e q u i r e d s e n s e r e s i s t o r ( R S )
1 6 S u b m i t D o c u m e n t a t i o n F e e d b a c k
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P W M C o n t r o l W i t h S e p a r a t e E n a b l e
Enable (EN)
VIN
CTRL
SW
OVP
GND
FB
LED
RS
PWM Brightness Control
100 Hz to 50 kHz
Enable (EN)
PWM Brightness Control100 Hz to 50 kHz
VIN
CTRL
SW
OVP
LED
FB
GND
RS
VIN
CTRL
SW
OVP
GND
FB
LED
RS
PWM Brightness Control
100 Hz to 50 kHz
Enable (EN)
L a y o u t C o n s i d e r a t i o n s
T h e r m a l C o n s i d e r a t i o n s
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
T h e c o n t r o l p i n ( C T R L ) c o m b i n e s t h e e n a b l e f u n c t i o n a s w e l l a s t h e P W M b r i g h t n e s s c o n t r o l f u n c t i o n i n o n e p i n . F o r s o m e s y s t e m s a n i n d e p e n d e n t e n a b l e f u n c t i o n i s r e q u i r e d . O n e w a y t o i m p l e m e n t t h i s i s t o u s e t h e b r i g h t n e s s c o n t r o l c o n f i g u r a t i o n a s s h o w n i n t h e p r e v i o u s s e c t i o n F i g u r e 1 8 .
O t h e r p o s s i b l e s o l u t i o n s a r e s h o w n i n F i g u r e 1 9 , F i g u r e 2 0 , F i g u r e 2 1 .
F i g u r e 1 9 . S e p a r a t e E n a b l e a n d P W M C o n t r o l U s i n g a S c h o t t k y D i o d e
F i g u r e 2 0 . S e p a r a t e E n a b l e a n d P W M C o n t r o l U s i n g a T r a n s i s t o r
F i g u r e 2 1 . S e p a r a t e E n a b l e a n d P W M C o n t r o l U s i n g a n A N D G a t e
I n a l l s w i t c h i n g p o w e r s u p p l i e s t h e l a y o u t i s a n i m p o r t a n t s t e p i n t h e d e s i g n , e s p e c i a l l y a t h i g h p e a k c u r r e n t s a n d s w i t c h i n g f r e q u e n c i e s . I f t h e l a y o u t i s n o t c a r e f u l l y d o n e , t h e r e g u l a t o r m i g h t s h o w n o i s e p r o b l e m s a n d d u t y c y c l e j i t t e r .
T h e i n p u t c a p a c i t o r s h o u l d b e p l a c e d a s c l o s e a s p o s s i b l e t o t h e i n p u t p i n f o r g o o d i n p u t v o l t a g e f i l t e r i n g . T h e i n d u c t o r a n d d i o d e m u s t b e p l a c e d a s c l o s e a s p o s s i b l e t o t h e s w i t c h p i n t o m i n i m i z e n o i s e c o u p l i n g i n t o o t h e r c i r c u i t s . S i n c e t h e f e e d b a c k p i n a n d n e t w o r k i s a h i g h i m p e d a n c e c i r c u i t , t h e f e e d b a c k n e t w o r k s h o u l d b e r o u t e d a w a y f r o m t h e i n d u c t o r .
T h e T P S 6 1 0 4 2 c o m e s i n a t h e r m a l l y e n h a n c e d Q F N p a c k a g e . T h e p a c k a g e i n c l u d e s a t h e r m a l p a d i m p r o v i n g t h e t h e r m a l c a p a b i l i t i e s o f t h e p a c k a g e . S e e t h e Q F N / S O N P C B A t t a c h m e n t a p p l i c a t i o n n o t e ( S L U A 2 7 1 ) .
T h e t h e r m a l r e s i s t a n c e j u n c t i o n t o a m b i e n t R J A o f t h e Q F N p a c k a g e g r e a t l y d e p e n d s o n t h e P C B l a y o u t . U s i n g t h e r m a l v i a s a n d w i d e P C B t r a c e s i m p r o v e s t h e t h e r m a l r e s i s t a n c e R J A . U n d e r n o r m a l o p e r a t i o n c o n d i t i o n s n o P C B v i a s a r e r e q u i r e d f o r t h e t h e r m a l p a d . H o w e v e r , t h e t h e r m a l p a d m u s t b e s o l d e r e d t o t h e P C B .
1 7S u b m i t D o c u m e n t a t i o n F e e d b a c k
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L14.7 H
Coilcraft LPO1704472
VIN
1.8 V to 6 V
C(IN)4.7 F
CO1 F
Enable/PWM Brightness
Control 100 HZ to 50 kHz
VIN
CTRL
SW
OVP
LED
D1ZHCS400
FB
GND
RS13
RS
C(IN)4.7 F
Enable/PWM Brightness
Control 100 HZ to 50 kHz
VIN
1.8 V to 6 V
RS13
VIN
CTRL
SW
OVP
LED
D1ZHCS400
FB
GND
L14.7 H
SUMIDA CMD4D11
CO4.7 F
RS
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
F i g u r e 2 2 . T P S 6 1 0 4 2 W i t h 1 , 0 m m T o t a l S y s t e m H e i g h t . E f f i c i e n c y = 8 2 . 7 % @ V I = 3 . 0 V / 1 9 m A
F i g u r e 2 3 . T P S 6 1 0 4 2 W i t h L o w L E D R i p p l e C u r r e n t a n d H i g h e r A c c u r a c y U s i n g a 4 . 7 F O u t p u t C a p a c i t o r
1 8 S u b m i t D o c u m e n t a t i o n F e e d b a c k
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VIN
CTRL
SW
OVP
LED
FB
GND
VIN
2.7 V to 6 V
C(IN)4.7 F
L1Sumida CDRH3D166R8
6.8 H
CO1 F
RS13Enable/PWM Brightness
Control 100 HZ to 50 kHz
RS
D1Zetex ZHCS400
VIN
CTRL
SW
OVP
LED
FB
GND
Rs
R1 R2
VIN
2.7 V to 6 V
CIN4.7 F
L110.0H
Coilcraft DO1605T103MX
CO100 nF
RS6.5 Enable/PWM Brightness
Control 100 HZ to 50 kHz
D1Zetex ZHCS400
30 30
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
F i g u r e 2 4 . T P S 6 1 0 4 2 P o w e r i n g 6 L E D s , E f f i c i e n c y = 8 4 % @ V I = 3 . 6 V / 1 9 m A
F i g u r e 2 5 . T P S 6 1 0 4 2 P o w e r i n g 8 L E D s , E f f i c i e n c y = 8 1 % @ V I = 3 . 6 V / 1 8 . 6 m A
1 9S u b m i t D o c u m e n t a t i o n F e e d b a c k
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L14.7 H
VCC= 1.8 V to 6 V
C(IN)4.7 F
CO100 nF
Analog Brightness Control3.3 V LED Off
0 V ILED = 20 mA
RS13
VIN
CTRL
SW
OVP
LED
D1ZHCS400
FB
GND
R110 k
R2120 k
RS
L14.7 H
CIN4.7 F
CO100 nF
3.3 V PWM Signal
0 % LEDs on
100 % LEDs OffC
R
VIN
CTRL
SW
OVP
LED
D1ZHCS400
FB
GND
VCC= 1.8 V to 6 V
R110 k
R2120 k
RS13
RS
T P S 6 1 0 4 2
S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7
F i g u r e 2 6 . A d j u s t a b l e B r i g h t n e s s C o n t r o l U s i n g a n A n a l o g V o l t a g e
F i g u r e 2 7 . A l t e r n a t i v e A d j u s t a b l e B r i g h t n e s s C o n t r o l U s i n g P W M S i g n a l
2 0 S u b m i t D o c u m e n t a t i o n F e e d b a c k
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PACKAGING INFORMATION
Orderable Device Status (1) PackageType
PackageDrawing
Pins PackageQty
Eco Plan (2) Lead/Ball Finish MSL Peak Temp(3)
TPS61042DRBR ACTIVE SON DRB 8 3000 Green (RoHS &
no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
TPS61042DRBRG4 ACTIVE SON DRB 8 3000 Green (RoHS &no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
TPS61042DRBT ACTIVE SON DRB 8 250 Green (RoHS &no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
TPS61042DRBTG4 ACTIVE SON DRB 8 250 Green (RoHS &no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
(1) The marketing status values are defined as follows:ACTIVE:Product device recommended for new designs.LIFEBUY:TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.NRND:Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part ina new design.PREVIEW:Device has been announced but is not in production. Samples may or may not be available.OBSOLETE:TI has discontinued the production of the device.
(2)Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontentfor the latest availability information and additional product content details.TBD:The Pb-Free/Green conversion plan has not been defined.Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirementsfor all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be solderedat high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die andpackage, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHScompatible) as defined above.Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flameretardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it isprovided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to theaccuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to takereasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis onincoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limitedinformation may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TIto Customer on an annual basis.
PACKAGE OPTION ADDENDUM
www.ti.com 5-Mar-2007
Addendum-Page 1
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TAPE AND REEL INFORMATION
*All dimensions are nominal
Device PackageType
PackageDrawing
Pins SPQ ReelDiameter
(mm)
ReelWidth
W1 (mm)
A0 (mm) B0 (mm) K0 (mm) P1(mm)
W(mm) Q
TPS61042DRBR SON DRB 8 3000 330.0 12.4 3.3 3.3 1.1 8.0 12.0
TPS61042DRBT SON DRB 8 250 180.0 12.4 3.3 3.3 1.1 8.0 12.0
PACKAGE MATERIALS INFORMATION
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*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
TPS61042DRBR SON DRB 8 3000 346.0 346.0 29.0
TPS61042DRBT SON DRB 8 250 190.5 212.7 31.8
PACKAGE MATERIALS INFORMATION
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IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements,and other changes to its products and services at any time and to discontinue any product or service without notice. Customers shouldobtain the latest relevant information before placing orders and should verify that such information is current and complete. All products aresold subject to TIs terms and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TIs standardwarranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where
mandated by government requirements, testing of all parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products andapplications using TI components. To minimize the risks associated with customer products and applications, customers should provideadequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right,or other TI intellectual property right relating to any combination, machine, or process in which