WT32i REFERENCE DESIGN - silabs.com · Bluegiga Technologies Oy Page 6 of 19 ... capacitors with 5%...
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WT32i REFERENCE DESIGN
APPLICATION NOTE
Monday, 26 May 2014
Version 1.1
Bluegiga Technologies Oy
Copyright © 2000-2014 Bluegiga Technologies
All rights reserved.
Bluegiga Technologies assumes no responsibility for any errors which may appear in this manual. Furthermore, Bluegiga Technologies reserves the right to alter the hardware, software, and/or specifications detailed here at any time without notice and does not make any commitment to update the information contained here. Bluegiga’s products are not authorized for use as critical components in life support devices or systems.
The WRAP is a registered trademark of Bluegiga Technologies
The Bluetooth trademark is owned by the Bluetooth SIG Inc., USA and is licensed to Bluegiga Technologies. All other trademarks listed herein are owned by their respective owners.
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VERSION HISTORY
Version Comment
1.0 First version
1.1 Schematic 4/5 corrected
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TABLE OF CONTENTS
1 Introduction ....................................................................................................................................................5
2 Hardware Design of DKWT32i v2 .................................................................................................................6
2.1 Choosing the Capacitors and Resistors Used in the Audio Path .........................................................6
2.2 How to Avoid Pops and Cracks When Powering the Board or Establishing A2DP connection ...........7
2.3 Schematic and Assembly of DKWT32i v2 ............................................................................................9
2.4 Layout of DKWT32i ............................................................................................................................ 15
2.5 RF, EMC and Audio Layout Considerations ...................................................................................... 17
3 Contact Information .................................................................................................................................... 19
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1 Introduction
This documents describes detailed the design of WT32i development kit.
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2 Hardware Design of DKWT32i v2
2.1 Choosing the Capacitors and Resistors Used in the Audio Path
Metal film resistors have lower noise than carbon resistors which makes them more suitable for high quality audio.
Non-linearity of capacitors within the audio path will have an impact on the audio quality at the frequencies where the impedance of the capacitors become dominant. At higher frequencies the amplitude is not determined by the value of the capacitors, but at the lower frequencies the impact of the capacitors will be seen.
Ceramic capacitors should be X5R or X7R type capacitors with relative high voltage rating. The higher the capacitance value, the lower is the frequency where the non-linearity will start to have an impact. Thus it is not a bad idea to select the capacitors value bigger than necessary from the frequency response point of view.
For optimal audio quality the best selection is to use film capacitors. Film capacitors have excellent linearity and they are non-polarized which makes them perfect choice for using in audio path. The drawback of film capacitors is bigger physical size and higher cost.
Figure 1 shows a modulation distortion measurement when using different type of capacitors in the audio paths. Modulation distortion measures the amount of distortion between two closely located sine waves. The difference between the different capacitors is obvious at low frequencies where the impedance of the capacitor is dominant.
Figure 1: Intermodulation distortion with different type of capacitors
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2.2 How to Avoid Pops and Cracks When Powering the Board or Establishing A2DP connection
Figure 2: Extenal audio PA connection
To match the impedances Z1 and Z2 it is important that the capacitors at the input of the amplifier are well matched together. The tolerance of a ceramic chip capacitor is typically in the range of 5% - 20% and generally ceramic capacitors are more accurate than film capacitors. Thus in this case ceramic X7R capacitors with 5% tolerance were chosen for the external audio PA to minimize the pop sound when the A2DP link is established or switched off.
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Figure 3: Equivalent circuit for simulating the transient caused by the impedance mismatch
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2.3 Schematic and Assembly of DKWT32i v2
Figure 4: DKWT32i v2 Schematic (1/5)
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U16 and U17 disconnec t UART converter when the cable is not plugged
2
1
3
5
6
4
U2
USBLC6-2
LDO 3v3
USB to UART
1TXD
2DTR
3RTS
4VDD_325
5RXD
6RI
7G
ND
8NC
9DSR
10DCD
11CTS
12SHTD
13EE_CLK
14EE_DATA
15 D+
16 D-
17VO_33
18
GN
D
19NC
20VDD_5
21
GN
D
22GP0
23GP1
24NC
25
GN
D_
A
26PLL_TEST
27OSC1
28OSC2
U3
PL2303HX
GID
D+
D-5
V
J4
C2
0
2.2
uF
/10
V/X
5R
/10
%
C4
1
2.2
uF
/10
V/X
5R
/10
%
1 2R16
27R, 50V, 0.063W, 1%
1 2R17
27R, 50V , 0.063W , 1%
12
R2
2
1.5
K,
50
V,
0.0
63
W,
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1 2R 25
5.1K , 50V , 0.063W , +/-5%
C4
0.1
uF
/10
V/X
5R
/10
%
2
1
3
5
6
4
U32
USBLC6-2
2
1
5
7
6
3
48 U16
74AUP2G126
2
1
5
7
6
3
48U17
74AUP2G126
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R3
10
K,
50
V,
0.0
63
W,
+/-
5%
GID
D+
D-5
V
J1
R11
3K , 50V , 0.063W , +/-5%
R1
2
5.1
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V,
0.0
63
W,
+/-
5%
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R2
8
1.5
K,
50
V,
0.0
63
W,
+/-
5%
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D3
DIO
/SC
HO
TT
KY
/MB
RA
14
0/1
A/4
0V
12
D7
DIO
/SC
HO
TT
KY
/MB
RA
14
0/1
A/4
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L1
3
1k
oh
m@
10
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Hz
, D
C 0
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hm
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4
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oh
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hm
X 4S HORTING_LIN K
J14-9J14-10
3V 3
3V 3
P IO8/US B _DE T
D-
D+
P IO2/US B _P ULL-UP
U A RT_TX
U A RT_RX
U A RT_RTS
U A RT_CTS
V B U S
Figure 5: DKWT32i v2 Schematic (2/5)
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Figure 6: DKWT32i v2 Schematic (3/5)
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Figure 7: DKWT32i v2 Schematic (4/5)
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Software I2C interface to configure the I2S codec
15MIC B IA S
10MIC 1L/LIN E 1L
12MIC 2L/LIN E 2L
13MIC 2R/LINE 2R
14MIC 3L/LIN E 3L
16MIC 3R/LINE 3R
11MIC 1R/LINE 1R
23
HP
RO
UT
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HP
LO
UT
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HP
LC
OM
22
HP
RC
OM
29
RIG
HT
_L
OP
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RIG
HT
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27
LE
FT
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LE
FT
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21D RV S S
26A V S S _DA C
17A V S S _A DC
6DV S S
32DV DD
7IOV DD
24DRV D D
18DRV D D
25A V DD_DA C
4D
IN
5D
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T
3W
CL
K
2B
CL
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1M
CL
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RE
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DA
8S
CL
33GND
34GND
35GND
36GND
U9
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1RS T
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4MR
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U10
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1
2
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4A
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7
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/10
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/10
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2
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F/6
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R 38
4.7K , 50V , 0.063W , 5%
R 40
4.7K , 50V , 0.063W , 5%
1
2
U11
RCA _RE D
1
2
U12
RCA _W HITE
1S LE E V E
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2TIP
J8
S J-3523-S MT-TR
C 33
330uF/6.3V /20% /TA N/E S R<10mohm
C 34
330uF/6.3V /20% /TA N/E S R<10mohm
1
2
U15
RCA _RE D
1
2
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RCA _W HITE
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C35
1uF/16V /20%
C36
1uF/16V /20%
C39
1uF/16V /20%
C40
1uF/16V /20%
1
3
5
2
4
6
J17
1 3 52 4 6
J1
8
1 3 52 4 6
J1
9
1
3
5
2
4
6
J12
R6
4
1M
, 5
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, 0
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, 5
%
R6
5
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, 5
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, 0
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, 5
%
R6
6
NP
R6
7
NP
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/10
V/X
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/10
%
C5
4
0.1
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/10
V/X
5R
/10
%
12
R 46
1M, 50V , 0.1W , 5%
12
R 49
1M, 50V , 0.1W , 5%
1IN
3G
ND
2OUT
U8
A P 7313C4
2
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F/6
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R/1
0%
C4
3
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F/6
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0%
I2S
_S
CK
I2S
_W
S
I2S
_S
DIN
I2S
_S
DO
UT
R E S E T
3V 3
3V 3
PIO
6/I
2C
_S
CL
PIO
7/I
2C
_S
DA
3V 3
Figure 8: DKWT32i v2 Schematic (5/5)
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Figure 9: WT32i Development Board Assembly Drawing
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2.4 Layout of DKWT32i
Figure 10: Top layer layout of DKWT32i contains signal and audio tracing
Figure 11: 2nd layer layout of DKWT32i contains a solid GND plane
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Figure 12: 3rd layer layout of DKWT32i contains supply voltages
Figure 13: Bottom layer layout of DKWT32i contains GND and signal tracing
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2.5 RF, EMC and Audio Layout Considerations
GND planes are stitched with vias at the edgesOf the PCB to prevent emissions
GND vias are placed right next to any GND pad to connectGND pads directly to the solid GND plane. This is to makesure that the return current path is low impedance withoutany loops.
Figure 14: GND vias in DKWT32i
Differential audio signals are traced parallelto make sure they have perfect common mode rejection . All the audio traces are routed on asolid GND plane.
Figure 15: Routing of differential audio signals
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Metal clearance area under the antenna. Antenna placed at the edge of the PCB.
GND plane is required on both sides of theAntenna. The antenna uses the GND plane as a part of radiator and the lack of GND planewill signifficantly reduce the performance.
Figure 16: Clearance area under the antenna
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3 Contact Information
Sales: [email protected]
Technical Support: www.bluegiga.com/support
Orders: [email protected]
WWW: www.bluegiga.com
www.bluegiga.hk
Head Office / Finland:
Phone: +358-9-4355 060
Fax: +358-9-4355 0660
Sinikalliontie 5A
02630 ESPOO
FINLAND
Postal address / Finland:
P.O. BOX 120
02631 ESPOO
FINLAND
Sales Office / USA:
Phone: +1 770 291 2181
Fax: +1 770 291 2183
Bluegiga Technologies, Inc.
3235 Satellite Boulevard, Building 400, Suite 300
Duluth, GA, 30096, USA
Sales Office / Hong-Kong:
Phone: +852 3972 2186
Bluegiga Technologies Ltd.