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TJA1054AT

Fault-tolerant CAN transceiver

NXP Semiconductors. 

NXP Semiconductors

TJA1054A

Fault-tolerant CAN transceiver

A local wake-up through pin WAKE is detected by a rising or falling edge with a

consecutive level exceeding the maximum specified tWAKE.

On a wake-up request the transceiver will set the output on pin INH to HIGH which can be

used to activate the external supply voltage regulator.

If VCC is provided the wake-up request can be read on the ERR or RXD outputs, so the

external microcontroller can activate the transceiver (switch to normal operating mode) via

pins STB and EN.

To prevent a false remote wake-up due to transients or RF fields, the wake-up voltage

levels have to be maintained for a certain period of time. In the low power modes the

failure detection circuit remains partly active to prevent an increased power consumption

in the event of failures 3, 3a, 4 and 7.

To prevent a false local wake-up during an open wire at pin WAKE, this pin has a weak

pull-up current source towards VBAT. However, in order to protect the transceiver against

any EMC immunity issues, it is recommended to connect a not used pin WAKE to pin

BAT. Pin INH is set to floating only if the goto-sleep command is entered successfully. To

enter a successful goto-sleep command under all conditions, this command must be kept

stable for the maximum specified th(sleep).

Pin INH will be set to a HIGH level again by the following events only:

• VBAT power-on (cold start)

• Rising or falling edge on pin WAKE

• A message frame with a dominant phase of at least the maximum specified t(CANH) or

t(CANL), while pin EN or pin STB is at a LOW level

• Pin STB goes to a HIGH level with VCC active

To provide fail-safe functionality, the signals on pins STB and EN will internally be set to

LOW when VCC is below a certain threshold voltage (VCC(stb)).

7.3 Power-on

After power-on (VBAT switched on) the signal on pin INH will become HIGH and an internal

power-on flag will be set. This flag can be read in the power-on standby mode through

pin ERR (STB = HIGH; EN = LOW) and will be reset by entering the normal operating

mode.

7.4 Protections

A current limiting circuit protects the transmitter output stages against short-circuit to

positive and negative battery voltage.

If the junction temperature exceeds the typical value of 165 °C, the transmitter output

stages are disabled. Because the transmitter is responsible for the major part of the power

dissipation, this will result in a reduced power dissipation and hence a lower chip

temperature. All other parts of the device will continue to operate.

The pins CANH and CANL are protected against electrical transients which may occur in

an automotive environment.

TJA1054A_5

Product data sheet

Rev. 05 — 29 September 2009

© NXP B.V. 2009. All rights reserved.

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