LTC6820
isoSPI Isolated
Communications Interface
FEATURES DESCRIPTION
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1Mbps Isolated SPI Data Communications The LTC 6820 provides bidirectional SPI communications
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Simple Galvanic Isolation Using Standard between two isolated devices through a single twisted-
Transformers pair connection. Each LTC6820 encodes logic states into
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Bidirectional Interface Over a Single Twisted Pair signals that are transmitted across an isolation barrier to
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Supports Cable Lengths Up to 100 Meters another LTC6820. The receiving LTC6820 decodes the
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Very Low EMI Susceptibility and Emissions transmission and drives the slave bus to the appropriate
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Configurable for High Noise Immunity or Low Power logic states. The isolation barrier can be bridged by a simple
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Engineered for ISO26262 Compliant Systems pulse transformer to achieve hundreds of volts of isolation.
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Requires No Software Changes in Most SPI Systems
The LTC6820 drives differential signals using matched
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Ultralow, 2A Idle Current
source and sink currents, eliminating the requirement
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Automatic Wake-Up Detection
for a transformer center tap and reducing EMI. Precision
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Operating Temperature Range: 40C to 125C
window comparators in the receiver detect the differential
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2.7V to 5.5V Power Supply
signals. The drive currents and the comparator thresholds
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Interfaces to All Logic from 1.7V to 5.5V
are set by a simple external resistor divider, allowing the
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Available in 16-Lead QFN and MSOP Packages
system to be optimized for required cable lengths and
desired signal-to-noise performance.
APPLICATIONS
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and isoSPI
is a trademark of Linear Technology Corporation. All other trademarks are the property of their
respective owners. Protected by U.S. patents, including 8908779.
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Industrial Networking
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Battery Monitoring Systems
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Remote Sensors
TYPICAL APPLICATION
Microcontroller to SPI Slave Isolated Interface Data Rate vs Cable Length
1.2
MASTER
CAT-5 ASSUMED
C LTC6820
1.0
MSTR
IP
MOSI
SDO
MISO 120 0.8
SDI
SCK
SCK
IM
CS
CS
0.6
0.4
100 METERS
TWISTED PAIR
REMOTE
0.2
SLAVE IC LTC6820
MSTR
0
IP
1 10 100
SDI
MOSI
120 CABLE LENGTH (METERS)
SDO
MISO
6820 TA01b
SCK IM
SCK
6820 TA01a
CS
CS
6820fb
1
For more information www.linear.com/LTC6820
DATA RATE (Mbps)LTC6820
ABSOLUTE MAXIMUM RATINGS (Notes 1, 2, 3)
Input Supply Voltages (V and V ) to GND ...........6V Specified Temperature Range
DD DDS
Pin Voltages LTC6820I .............................................40C to 85C
SCK, CS, EN ...............0.3V to V + 0.3V (6V Max) LTC6820H .......................................... 40C to 125C
DDS
IBIAS, SLOW, IP, IM .....0.3V to V + 0.3V (6V Max) Storage Temperature Range .................. 65C to 150C
DD
All Other Pin Voltages .............................. 0.3V to 6V Lead Temperature (Soldering, 10 sec)
Maximum Source/Sink Current MSOP ...............................................................300C
IP, IM .................................................................30mA
MOSI, MISO, SCK, CS ........................................20mA
Operating Temperature Range
LTC6820I .............................................40C to 85C
LTC6820H .......................................... 40C to 125C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
16 15 14 13
EN 1 16 IBIAS
MOSI 1 12 SLOW
MOSI 2 15 ICMP
MISO 3 14 GND
MISO 2 11 MSTR
17 SCK 4 13 SLOW
SCK 3 10 IP
CS 5 12 MSTR
V 6 11 IP
DDS
CS IM
4 9
POL 7 10 IM
PHA 8 9 V
5 6 7 8
DD
MS PACKAGE
16-LEAD PLASTIC MSOP
UD PACKAGE
T = 150C, = 120C/W
JMAX JA
16-LEAD (3mm 3mm) PLASTIC QFN
T = 150C, = 58.7C/W
JMAX JA
EXPOSED PAD (PIN 17) PCB CONNECTION TO GND IS OPTIONAL