ISL72026SEH Datasheet, PDF (10/18 Pages) Intersil Corporation – 3.3V Radiation Tolerant CAN Transceiver, 1Mbps, Listen Mode, Loopback

ISL72026SEH
Test Circuits and Waveforms (Continued)
GND _D
CANH
I_O(SRT)
CANL
GND
I_O(SRT)
+- _{VIN = -7V}
OR 12V
0A
V_IN
0V
V_IN
10ms
|I_O(SRT)|
12V
-7V
FIGURE 19A. OUTPUT SHORT CIRCUIT CURRENT TEST CIRCUIT
FIGURE 19B. OUTPUT SHORT CIRCUIT CURRENT WAVEFORMS
FIGURE 19. OUTPUT SHORT CIRCUIT CURRENT
Functional Description
Overview
The Intersil ISL72026SEH is a 3.3V radiation tolerant CAN
transceiver that is compatible with the ISO11898-2 standard for
use in CAN (Controller Area Network) serial communication
systems.
The device performs transmit and receive functions between the
CAN controller and the CAN differential bus. It can transmit and
receive at bus speeds of up to 1Mbps. It is designed to operate
over a common mode range of -7V to +12V with a maximum of
120 nodes. The device is capable of withstanding ±20V on the
CANH and CANL bus pins outside of ion beam and ±16V under
ion beam.
Slope Adjustment
The output driver rise and fall time has three distinct selections
that may be chosen by using a resistor from the RS pin to GND.
Connecting the RS pin directly to GND results in output switching
times that are the fastest, limited only by the drive capability of
the output stage. RS = 10kΩ provides for a typical slew rate of
8V/µs and RS = 50kΩ provides for a typical slew rate of 4V/µs.
Putting a high logic level to the RS pin places the device in a low
current listen mode. The protocol controller uses this mode to
switch between low power listen mode and normal transmit
mode.
Cable Length
The device can work per ISO11898 specification with a 40m
cable and stub length of 0.3m and 60 nodes at 1Mbps. This is
greater than the ISO requirement of 30 nodes. The cable type
specified is twisted pair (shielded or unshielded) with a
characteristic impedance of 120Ω. Resistors equal to this are to
be terminated at both ends of the cable. Stubs should be kept as
short as possible to prevent reflections.
Cold Spare
High reliability system designers implementing data
communications have to be sensitive to the potential for single
point failures. To mitigate the risk of a failure they will use
redundant bus transceivers in parallel. In this arrangement both
active and quiescent devices can be present simultaneously on
the bus. The quiescent devices are powered down for cold spare
and do not affect the communication of the other active nodes.
To achieve this, a powered down transceiver (V_CC < 200mV) has
a resistance between the CANH or CANL bus pin and the V_CC
supply rail of > 480kΩ (max) with a typical resistance > 2MΩ. The
resistance between CANH and CANL of a powered-down
transceiver has a typical resistance of 80kΩ.
Listen Mode
When a high level is applied to the RS pin, the device enters a low
power listen mode. The driver of the transceiver is switched off to
conserve power while the receiver remains active. In listen mode
the transceiver draws 2mA (max) of current.
A low level on the RS pin brings the device back to normal
operation.
Loopback Mode
When a high level is applied to the LBK pin, the device enters the
loopback state. The transceiver CANH and CANL pins are
disconnected from the bus. The driver and receiver circuitry of
the transceiver remains active to allow for diagnostic testing of
the node.
Using 3.3V Devices in 5V Systems
Looking at the differential voltage of both the 3.3V and 5V
devices, the differential voltage is the same, the recessive
common mode output is the same. The dominant common
mode output voltage is slightly lower than the 5V counterparts.
The receiver specs are also the same. Though the electrical
parameters appear compatible it is advised that necessary
system testing be performed to verify interchangeable operation.
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FN8762.1
November 9, 2015