6.5kV Isolated RS485 + 1W Power - Analog Devices · 2018. 3. 20. · The LTM®2885 is an isolated...
2
The LTM ® 2885 is an isolated RS485 transceiver that guards against large ground-to-ground differentials. The LTM2885’s internal inductive isolation barrier breaks ground loops by isolating the logic level interface and line transceiver. An onboard DC/DC converter provides power to the transceiver with an isolated 5V supply output for powering additional system circuitry. With 6500V RMS galvanic isolation, onboard secondary power and a fully compliant RS485 transmitter and receiver, the LTM2885 requires no external components and provides a small, complete µModule ® solution for isolated serial data communications. Features n Isolator µModule Technology n Isolated RS485/RS422 Transceiver: 6500V RMS n Reinforced Insulation n 14.6mm Creepage and Clearance n Integrated Isolated, 1W DC/DC Converter n 5V at Up to 200mA n Low EMI n Integrated Selectable 120Ω Termination n Differential Output Voltage > 2.1V into 54Ω Supports PROFIBUS Applications n 20Mbps or Low EMI 250kbps Data Rate n High ESD: ±15kV HBM n Common Mode Transient Immunity: > 50kV/µs n Maximum Continuous Working Voltage: 690V RMS n Small Footprint (22mm × 9mm × 5.16mm) in Surface Mount BGA Package Complete 20Mbps µModule Transceiver Includes 6500V RMS Isolated Power No External Components Required 6.5kV Isolated RS485 + 1W Power 3.3V or 5V 5V RS485/RS422 Bus RO DI ON REG 6.5kV RMS Galvanic Isolation Isolated LTM2885 Power EMI Performance Chart FREQUENCY (MHz) 0 –30 dBμV/m –20 0 10 20 600 700 800 900 60 –10 100 200 300 400 500 1000 30 40 50 GTEM Radiated Emission Scan Corrected Per IEC 61000-4-20 Detector = Peak RBW = 120kHz, VBW = 300kHz SWEEP TIME = 680ms # OF POINTS = 8084 Measured on LTM2885 Demo Circuit 1794A Driver Terminated R TERM = 120Ω 6dB Safety Margin LTM2885 CISPR 22 Class B Limit L, LT, LTC, LTM, Linear Technology, the Linear logo and µModule are registered trademarks and the Isolator logo is a trademark of Analog Devices, Inc. All other trademarks are the property of their respective owners.
Transcript of 6.5kV Isolated RS485 + 1W Power - Analog Devices · 2018. 3. 20. · The LTM®2885 is an isolated...
-
The LTM®2885 is an isolated RS485 transceiver that guards against large ground-to-ground differentials. The LTM2885’s internal inductive isolation barrier breaks ground loops by isolating the logic level interface and line transceiver. An onboard DC/DC converter provides power to the transceiver with an isolated 5V supply output for powering additional system circuitry. With 6500VRMS galvanic isolation, onboard secondary power and a fully compliant RS485 transmitter and receiver, the LTM2885 requires no external components and provides a small, complete µModule® solution for isolated serial data communications.
Features n Isolator µModule Technology n Isolated RS485/RS422 Transceiver: 6500VRMS n Reinforced Insulation n 14.6mm Creepage and Clearance n Integrated Isolated, 1W DC/DC Converter
n 5V at Up to 200mA n Low EMI
n Integrated Selectable 120Ω Termination n Differential Output Voltage > 2.1V into 54Ω
Supports PROFIBUS Applications n 20Mbps or Low EMI 250kbps Data Rate n High ESD: ±15kV HBM n Common Mode Transient Immunity: >50kV/µs n Maximum Continuous Working Voltage: 690VRMS n Small Footprint (22mm × 9mm × 5.16mm)
in Surface Mount BGA Package
Complete 20Mbps µModule Transceiver Includes 6500VRMS Isolated Power No External Components Required
6.5kV Isolated RS485 + 1W Power3.3V or 5V
5V
RS485/RS422Bus
RO
DI
ON
REG
6.5kVRMS Galvanic Isolation
Isolated
LTM2885
Power
EMI Performance Chart
FREQUENCY (MHz)0
–30
dBµV
/m
–20
0
10
20
600 700 800 900
60
–10
100 200 300 400 500 1000
30
40
50
GTEM Radiated Emission ScanCorrected Per IEC 61000-4-20Detector = PeakRBW = 120kHz, VBW = 300kHzSWEEP TIME = 680ms# OF POINTS = 8084
Measured on LTM2885 Demo Circuit 1794ADriver Terminated RTERM = 120Ω
6dB Safety Margin
LTM2885CISPR 22 Class B Limit
L, LT, LTC, LTM, Linear Technology, the Linear logo and µModule are registered trademarks and the Isolator logo is a trademark of Analog Devices, Inc. All other trademarks are the property of their respective owners.
-
Isolated µModule Technology
Isolated Supply Voltage Output
Common Mode Transient Immunity
Integrated Selectable 120Ω Termination
To achieve greater than 6500VRMS isolation, the LTM2885 utilizes Isolator µModule technology, which includes coupled signal inductors embedded in the µModule substrate. This technique ensures consistent ruggedness and reliability, and will be certified by UL and CSA to guarantee the isolation barrier’s effectiveness. The μModule package integrates several technologies to deliver a cost-effective, advanced solution that minimizes board space and improves electrical and thermal performance.
Unlike other isolated solutions, the LTM2885 allows communication through common mode transient events, greater than 50kV/µs, unaffected by the transient and without introducing any priority data jitter or data corruption.
The LTM2885 is not only self-powered, but also provides a well regulated 5V, up to 1W, isolated supply for powering any supporting components on the isolated bus side. This regulated power is continuously available over the operating temperature range, even while driving full RS485 compliant signal levels.
A pin-selectable 120Ω termination is available for minimizing reflections that may be present on an unterminated transmission line. RS485 networks require 120Ω termination resistors to be installed by the end-user based on the physical layout of the twisted-pair wires and the placement of the nodes. The LTM2885’s pin-selectable termination allows the proper nodes to be terminated by switching the integrated termination on or off, under software control, without the need of physical intervention by the user.
ARO
TE
REB
GALVAN
ICISOL
ATION
TEMPERATURE (°C)–50 –25 0 25 50 75 100 125
50
75
100
125
150
175
200
225
250
275
300
I CC2
CUR
RENT
(mA)
R485 = OPEN, C485 = 0pF, 0Mbps, VCM = 0VR485 = 54Ω, C485 = 500pF, 10Mbps, VCM = –7V
VCC = 5.0V, VCC2 ≥ 4.75V
ON
VL
RO
RE
DE
DI
TE
VCC
DOUT NC NC DIN SLO
GND2 Y
Z
B
A
VCC2
A B P R S TC D E F G H J K L M N
1
2
3
4
5
6
7
GND
BGA PACKAGE42-PIN (22mm × 9mm × 5.2mm)
TOP VIEW
5V/DIV
5V/DIV
20ns/DIV
300V/DIV
DI
MULTIPLE SWEEPSOF COMMON MODE
TRANSIENTS
RO
1116
www.linear.com/2885 n 1-800-4-LINEAR
http://www.linear.com/2885
