TJA1041A データシートの表示（PDF） - Philips Electronics

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TJA1041A

High speed CAN transceiver

Philips Electronics 

Philips Semiconductors

High speed CAN transceiver

Product specification

TJA1041A

UVNOM FLAG

UVNOM is the VCC and VI/O undervoltage detection flag.

The flag is set when the voltage on pin VCC drops below

VCC(sleep) for longer than tUV(VCC) or when the voltage on

pin VI/O drops below VI/O(sleep) for longer than tUV(VI/O).

When the UVNOM flag is set, the transceiver will enter

sleep mode to save power and not disturb the bus. In sleep

mode the voltage regulators connected to pin INH are

disabled, avoiding the extra power consumption in case of

a short-circuit condition. After a waiting time (fixed by the

same timers used for setting UVNOM) any wake-up request

or setting of the pwon flag will clear UVNOM and the timers,

allowing the voltage regulators to be reactivated at least

until UVNOM is set again.

UVBAT FLAG

UVBAT is the VBAT undervoltage detection flag. The flag is

set when the voltage on pin VBAT drops below VBAT(stb).

When UVBAT is set, the transceiver will try to enter standby

mode to save power and not disturb the bus. UVBAT is

cleared when the voltage on pin VBAT has recovered. The

transceiver will then return to the operating mode

determined by the logic state of pins STB and EN.

PWON FLAG

Pwon is the VBAT power-on flag. This flag is set when the

voltage on pin VBAT has recovered after it dropped below

VBAT(pwon), particularly after the transceiver was

disconnected from the battery. By setting the pwon flag,

the UVNOM flag and timers are cleared and the transceiver

cannot enter sleep mode. This ensures that any voltage

regulator connected to pin INH is activated when the node

is reconnected to the battery. In pwon/listen-only mode the

pwon flag can be made available on pin ERR. The flag is

cleared when the transceiver enters normal mode.

WAKE-UP FLAG

The wake-up flag is set when the transceiver detects a

local or a remote wake-up request. A local wake-up

request is detected when a logic state change on

pin WAKE remains stable for at least twake. A remote

wake-up request is detected after two bus dominant states

of at least tBUSdom (with each dominant state followed by a

recessive state of at least tBUSrec). The wake-up flag can

only be set in standby mode, go-to-sleep command mode

or sleep mode. Setting of the flag is blocked during the

UVNOM flag waiting time. By setting the wake-up flag, the

UVNOM flag and timers are cleared. The wake-up flag is

immediately available on pins ERR and RXD (provided

that VI/O and VCC are present). The flag is cleared at

power-on, or when the UVNOM flag is set or the transceiver

enters normal mode.

WAKE-UP SOURCE FLAG

Wake-up source recognition is provided via the wake-up

source flag, which is set when the wake-up flag is set by a

local wake-up request via pin WAKE. The wake-up source

flag can only be set after the pwon flag is cleared.

In normal mode the wake-up source flag can be made

available on pin ERR. The flag is cleared at power-on or

when the transceiver leaves normal mode.

BUS FAILURE FLAG

The bus failure flag is set if the transceiver detects a bus

line short-circuit condition to VBAT, VCC or GND during four

consecutive dominant-recessive cycles on pin TXD, when

trying to drive the bus lines dominant. In normal mode the

bus failure flag can be made available on pin ERR. The

flag is cleared when the transceiver re-enters normal

mode.

LOCAL FAILURE FLAG

In normal mode or pwon/listen-only mode the transceiver

can recognize five different local failures, and will combine

them into one local failure flag. The five local failures are:

TXD dominant clamping, RXD recessive clamping, a

TXD-to-RXD short circuit, bus dominant clamping, and

over-temperature. Nature and detection of these local

failures is described in Section “Local failures”.

In pwon/listen-only mode the local failure flag can be made

available on pin ERR. The flag is cleared when entering

normal mode or when RXD is dominant while TXD is

recessive, provided that all local failures are resolved.

Local failures

The TJA1041A can detect five different local failure

conditions. Any of these failures will set the local failure

flag, and in most cases the transmitter of the transceiver

will be disabled. The following sections give the details.

TXD DOMINANT CLAMPING DETECTION

A permanent LOW level on pin TXD (due to a hardware or

software application failure) would drive the CAN bus into

a permanent dominant state, blocking all network

communication. The TXD dominant time-out function

prevents such a network lock-up by disabling the

transmitter of the transceiver if pin TXD remains at a LOW

level for longer than the TXD dominant time-out tdom(TXD).

2004 Feb 20

9

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