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TJA1054T

Fault-tolerant CAN transceiver

Philips Electronics 

Philips Semiconductors

Fault-tolerant CAN transceiver

Preliminary specification

TJA1054

Low power modes

The transceiver provides 3 low power modes which can be

entered and exited via pins STB and EN (see Table 2 and

Fig.3).

The Sleep mode is the mode with the lowest power

consumption. Pin INH is switched to high-impedance for

deactivation of the external voltage regulator. Pin CANL is

biased to the battery voltage via pin RTL. If the supply

voltage is provided pins RXD and ERR will signal the

wake-up interrupt signal.

The standby mode will react the same as the Sleep mode

but with a HIGH-level on pin INH.

The power-on standby mode is the same as the standby

mode with the battery power-on flag instead of the

wake-up interrupt signal on pin ERR. The output on

pin RXD will show the wake-up interrupt. This mode is only

for reading out the power-on flag.

Wake-up requests are recognized by the transceiver when

a dominant signal is detected on either bus line or if

pin WAKE detects an edge (rising or falling) which stays

longer HIGH or LOW respectively during a certain period

of time. On a wake-up request the transceiver will set the

output on pin INH 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

wake-up the transceiver (switch to normal operating

mode) via pins STB and EN.

To prevent false 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.

Pin INH is set to floating only during the goto-sleep

command and stays floating during the Sleep mode. If

pin INH is set to floating, pin INH will not be set to

HIGH-level again just by a mode change to normal

operating mode. Pin INH will be set to HIGH-level by the

following events only:

• power-on (VBAT switching-on at cold start)

• rising or falling edge on pin WAKE

• a message with 5 consecutive dominant bits during

pin EN or pin STB is at LOW-level.

The signals on pins STB and EN will internally be set to

LOW-level when VCC is below a certain threshold voltage

so providing fail safe functionality.

Table 2 Normal operating and low power modes

MODE

Goto-sleep

command

Sleep

Standby

Power-on

standby

Normal

operating

STB

0

0

0

1

1

ERR

EN

LOW

1

wake-up interrupt

0(1)

signal;

notes 2 and 3

0

0 VBAT power-on flag;

notes 2 and 4

HIGH

1 error flag

no error

flag

RXD

LOW

HIGH

RTL

SWITCHED

TO

wake-up interrupt

signal;

notes 2 and 3

wake-up interrupt

signal;

notes 2 and 3

dominant

received data

recessive

received data

VBAT

VBAT

VBAT

VBAT

VCC

Notes

1. In case the goto-sleep command was used before. When VCC drops pin EN will become LOW, but this does not effect

the internal functions due to the fail safe functionality.

2. If the supply voltage VCC is present.

3. Wake-up interrupts are released when entering the normal operating mode.

4. VBAT power-on flag will be reset when entering the normal operating mode.

1999 Feb 11

7

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