TJA1042

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© NXP B.V. 2012. All rights reserved.

Product data sheet

Rev. 7 — 8 May 2012

5 of 22

NXP Semiconductors

TJA1042

High-speed CAN transceiver with Standby mode

7.

Functional description

The TJA1042 is a HS-CAN stand-alone transceiver with Standby mode. It combines the

functionality of the PCA82C250, PCA82C251 and TJA1040 transceivers with improved

EMC and ESD handling capability and quiescent current performance. Improved slope

control and high DC handling capability on the bus pins provide additional application

flexibility.

The TJA1042 is available in two versions, distinguished only by the function of pin 5:

existing PCA82C250 and PCA82C251 applications

supply voltages down to 3 V

7.1 Operating modes

The TJA1042 supports two operating modes, Normal and Standby, which are selected via

pin STB. See Table 4 for a description of the operating modes under normal supply

conditions.

7.1.1 Normal mode

A LOW level on pin STB selects Normal mode. In this mode, the transceiver can transmit

and receive data via the bus lines CANH and CANL (see Figure 1 for the block diagram).

The differential receiver converts the analog data on the bus lines into digital data which is

output to pin RXD. The slope of the output signals on the bus lines is controlled and

optimized in a way that guarantees the lowest possible EME.

7.1.2 Standby mode

A HIGH level on pin STB selects Standby mode. In Standby mode, the transceiver is not

able to transmit or correctly receive data via the bus lines. The transmitter and

Normal-mode receiver blocks are switched off to reduce supply current, and only a

low-power differential receiver monitors the bus lines for activity. The wake-up filter on the

output of the low-power receiver does not latch bus dominant states, but ensures that only

pin RXD.

In Standby mode, the bus lines are biased to ground to minimize the system supply

a wake-up request, a transition to Normal mode will not be triggered until STB is forced

LOW.

Table 4.

Operating modes

Mode

Pin STB

Pin RXD

LOW

HIGH

Normal

LOW

bus dominant

bus recessive

Standby

HIGH

wake-up request

detected

no wake-up request

detected