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TJA1021

LIN 2.1/SAE J2602 transceiver

NXP Semiconductors. 

NXP Semiconductors

TJA1021

LIN 2.1/SAE J2602 transceiver

Standby mode is signalled by a LOW-level on pin RXD which can be used as an interrupt

for the microcontroller.

In Standby mode (pin SLP_N is still LOW), the condition of pin TXD (weak pull-down or

strong pull-down) indicates the wake-up source: weak pull-down for a remote wake-up

request and strong pull-down for a local wake-up request.

Setting pin SLP_N HIGH during Standby mode results in the following events:

• An immediate reset of the wake-up source flag; thus releasing the possible strong

pull-down at pin TXD before the actual mode change (after tgotonorm) is performed

• A change into Normal mode if the HIGH level on pin SLP_N has been maintained for

a certain time period (tgotonorm)

• An immediate reset of the wake-up request signal on pin RXD

7.4 Normal mode

In Normal mode the TJA1021 is able to transmit and receive data via the LIN bus line. The

receiver detects the data stream at the LIN bus input pin and transfers it via pin RXD to

the microcontroller (see Figure 1): HIGH at a recessive level and LOW at a dominant level

on the bus. The receiver has a supply-voltage related threshold with hysteresis and an

integrated filter to suppress bus line noise. The transmit data stream of the protocol

controller at the TXD input is converted by the transmitter into a bus signal with optimized

slew rate and wave shaping to minimize EME. The LIN bus output pin is pulled HIGH via

an internal slave termination resistor. For a master application an external resistor in

series with a diode should be connected between pin INH or VBAT on one side and pin LIN

on the other side (see Figure 7).

When in Sleep, Standby or Power-up mode, the TJA1021 enters Normal mode whenever

a HIGH level on pin SLP_N is maintained for a time of at least tgotonorm.

The TJA1021 switches to Sleep mode in case of a LOW-level on pin SLP_N, maintained

for a time of at least tgotosleep.

7.5 Wake-up

When VBAT exceeds the power-on-reset threshold voltage Vth(POR)H, the TJA1021 enters

Power-on mode. Though the TJA1021 is powered-up and INH is HIGH, both the

transmitter and receiver are still inactive. If SLP_N = 1 for t > tgotonorm, the TJA1021 enters

Normal mode.

There are three ways to wake-up a TJA1021 which is in Sleep mode:

1. Remote wake-up via a dominant bus state of at least twake(dom)LIN

2. Local wake-up via a negative edge at pin WAKE_N

3. Mode change (pin SLP_N is HIGH) from Sleep mode to Normal mode

7.6 Remote and local wake-up

A falling edge at pin LIN followed by a LOW level maintained for a certain time period

(twake(dom)LIN) and a rising edge at pin LIN respectively (see Figure 4) results in a remote

wake-up. It should be noted that the time period twake(dom)LIN is measured either in Normal

mode while TXD is HIGH, or in Sleep mode irrespective of the status of pin TXD.

TJA1021

Product data sheet

All information provided in this document is subject to legal disclaimers.

Rev. 6 — 30 December 2010

© NXP B.V. 2010. All rights reserved.

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