TJA1055
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© NXP B.V. 2013. All rights reserved.
Product data sheet
Rev. 5 — 6 December 2013
6 of 26
NXP Semiconductors
TJA1055
Enhanced fault-tolerant CAN transceiver
[1]
A weak termination implies a pull-down current source behavior of 75
A typical.
[2]
A weak termination implies a pull-up current source behavior of 75
A typical.
Failure 6 is detected if the CANL bus line exceeds its comparator threshold for a certain
period of time. This delay is needed to avoid false triggering by external RF fields. After
detection of failure 6, the reception is switched to the single-wire mode through CANH; the
CANL driver is switched off and the RTL bias changes to the pull-up current source.
Recovery from failures 3, 3a and 6 is detected automatically after reading a consecutive
recessive level by corresponding comparators for a certain period of time.
Failures 4 and 7 initially result in a permanent dominant level on pin RXD. After a time-out
the CANL driver is switched off and the RTL bias changes to the pull-up current source.
Reception continues by switching to the single-wire mode via pins CANH or CANL. When
failures 4 or 7 are removed, the recessive bus levels are restored. If the differential
voltage remains below the recessive threshold level for a certain period of time, reception
and transmission switch back to the differential mode.
If any of the wiring failure occurs, the output signal on pin ERR will be set to LOW. On
error recovery, the output signal on pin ERR will be set to HIGH again. In case of an
interrupted open bus wire, this failure will be detected and signalled only if there is an
open wire between the transmitting and receiving node(s). Thus, during open wire
failures, pin ERR typically toggles.
During all single-wire transmissions, EMC performance (both immunity and emission) is
worse than in the differential mode. The integrated receiver filters suppress any HF noise
induced into the bus wires. The cut-off frequency of these filters is a compromise between
propagation delay and HF suppression. In single-wire mode, LF noise cannot be
distinguished from the required signal.
Table 4.
Bus failures
Failure
Description
Termination
CANH (RTH)
Termination
CANL (RTL)
CANH
driver
CANL
driver
Receiver
mode
1
CANH wire
interrupted
on
on
on
on
differential
2
CANL wire interrupted on
on
on
on
differential
3
CANH short-circuited
to battery
weak
on
off
on
CANL
3a
CANH short-circuited
to V
CC
weak
on
off
on
CANL
4
CANL short-circuited
to ground
on
weak
on
off
CANH
5
CANH short-circuited
to ground
on
on
on
on
differential
6
CANL short-circuited
to battery
on
weak
on
off
CANH
6a
CANL short-circuited
to V
CC
on
on
on
on
differential
7
CANL and CANH
mutually
short-circuited
on
weak
on
off
CANH
