LTC6820_15 Datasheet, PDF (1/30 Pages) Linear Technology – isoSPI Isolated Communications Interface

LTC6820
isoSPI Isolated
Communications Interface
Features
Description
n _{1Mbps Isolated SPI Data Communications}
n _{Simple Galvanic Isolation Using Standard}
Transformers
n _{Bidirectional Interface Over a Single Twisted Pair}
n _{Supports Cable Lengths Up to 100 Meters}
n _{Very Low EMI Susceptibility and Emissions}
n _{Configurable for High Noise Immunity or Low Power}
n _{Engineered for ISO26262 Compliant Systems}
n _{Requires No Software Changes in Most SPI Systems}
n _{Ultralow, 2µA Idle Current}
n _{Automatic Wake-Up Detection}
n _{Operating Temperature Range: –40°C to 125°C}
n _{2.7V to 5.5V Power Supply}
n _{Interfaces to All Logic from 1.7V to 5.5V}
n _{Available in 16-Lead QFN and MSOP Packages}
Applications
n _{Industrial Networking}
n _{Battery Monitoring Systems}
n _{Remote Sensors}
The LTC^®6820 provides bidirectional SPI communications
between two isolated devices through a single twisted-
pair connection. Each LTC6820 encodes logic states into
signals that are transmitted across an isolation barrier to
another LTC6820. The receiving LTC6820 decodes the
transmission and drives the slave bus to the appropriate
logic states. The isolation barrier can be bridged by a simple
pulse transformer to achieve hundreds of volts of isolation.
The LTC6820 drives differential signals using matched
source and sink currents, eliminating the requirement
for a transformer center tap and reducing EMI. Precision
window comparators in the receiver detect the differential
signals. The drive currents and the comparator thresholds
are set by a simple external resistor divider, allowing the
system to be optimized for required cable lengths and
desired signal-to-noise performance.
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. Patents pending.
Typical Application
Microcontroller to SPI Slave Isolated Interface
MASTER
µC
SDO
SDI
SCK
CS
LTC6820
MSTR
MOSI ^IP
MISO
SCK _IM
CS
120Ω
REMOTE
SLAVE IC
SDI
SDO
SCK
CS
LTC6820
MSTR
IP
MOSI
MISO
SCK IM
CS
100 METERS
TWISTED PAIR
120Ω
6820 TA01a
Data Rate vs Cable Length
1.2
CAT-5 ASSUMED
1.0
0.8
0.6
0.4
0.2
0
1
10
100
CABLE LENGTH (METERS)
6820 TA01b
For more information www.linear.com/LTC6820
6820fa
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