NCV7342

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7

Over−temperature Detection

A thermal protection circuit protects the IC from damage

by switching off the transmitter if the junction temperature

exceeds a value of approximately 180

°C. Because the

transmitter dissipates most of the power, the power

dissipation and temperature of the IC is reduced. All other

IC functions continue to operate. The transmitter off−state

resets when the temperature decreases below the shutdown

threshold and pin TxD goes High. The thermal protection

circuit is particularly needed in case of a bus line failure.

TxD Dominant Time−out Function

A TxD dominant time−out timer circuit prevents the bus

lines being driven to a permanent dominant state (blocking

all network communication), if pin TxD is forced

permanently Low by a hardware and/or software application

failure. The timer is triggered by a negative edge on pin TxD.

If the duration of the low−level on pin TxD exceeds the

driving the bus into a recessive state. The timer is reset by a

positive edge on pin TxD.

minimum possible bit rate to 8 kbps.

Bus Dominant Time−out Function

Bus dominant time−out timer is started in the standby

mode when CAN bus changes from recessive to dominant

state. If the dominant state on the bus is kept for longer time

timer is reset when CAN bus changes from dominant to

recessive state. This feature prevents generating permanent

wake−up request by the bus clamped to the dominant level.

Fail Safe Features

A current−limiting circuit protects the transmitter output

stage from damage caused by an accidental short circuit to

either positive or negative supply voltage, although power

dissipation increases during this fault condition.

level will force transceiver to switch into the standby mode.

The logic level on pin STB will be ignored as long as

undervoltage condition is not recovered. (NCV7342−3

version only)

detection level will cause the transceiver to disengage from

(NCV7342−3 version only)

The pins CANH and CANL are protected against

automotive electrical transients (according to ISO 7637; see

Figure 6). Pins TxD and STB are pulled High internally

should the input become disconnected. Pins TxD, STB and

RxD will be floating, preventing reverse supply should the