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TJA1021

LIN 2.1/SAE J2602 transceiver

NXP Semiconductors. 

NXP Semiconductors

TJA1021

LIN 2.1/SAE J2602 transceiver

Table 4. Operating modes

Mode

SLP_N TXD (output)

Sleep mode 0

weak pull-down

Standby[1]

0

mode

weak pull-down if

remote wake-up;

strong pull-down if

local wake-up[2]

RXD

floating

LOW[3]

INH

floating

HIGH

Normal mode 1

Power-on mode 0

HIGH: recessive state HIGH: recessive state HIGH

LOW: dominant state LOW: dominant state

weak pull-down

floating

HIGH

Transmitter Remarks

off

no wake-up request

detected

off

wake-up request

detected; in this mode

the microcontroller

can read the wake-up

source: remote or

local wake-up

Normal mode [2][3][4]

off

[5]

[1] Standby mode is entered automatically upon any local or remote wake-up event during Sleep mode. Pin INH and the 30 k termination

resistor at pin LIN are switched on.

[2] The internal wake-up source flag (set if a local wake-up did occur and fed to pin TXD) will be reset after a positive edge on pin SLP_N.

[3] The wake-up interrupt (on pin RXD) is released after a positive edge on pin SLP_N.

[4] Normal mode is entered after a positive edge on SLP_N. As long as TXD is LOW, the transmitter is off. In the event of a short-circuit to

ground on pin TXD, the transmitter will be disabled.

[5] Power-on mode is entered after switching on VBAT.

7.2 Sleep mode

This mode is the most power-saving mode of the TJA1021. Despite its extreme low

current consumption, the TJA1021 can still be woken up remotely via pin LIN, or woken

up locally via pin WAKE_N, or activated directly via pin SLP_N. Filters at the inputs of the

receiver (LIN), of pin WAKE_N and of pin SLP_N prevent unwanted wake-up events due

to automotive transients or EMI. All wake-up events must be maintained for a certain time

period (twake(dom)LIN, twake(dom)WAKE_N and tgotonorm).

Sleep mode is initiated by a falling edge on pin SLP_N in Normal mode. To enter Sleep

mode successfully (INH becomes floating), the sleep command (pin SLP_N = LOW) must

be maintained for at least tgotosleep.

In Sleep mode the internal slave termination between pins LIN and VBAT is disabled to

minimize the power dissipation in the event that pin LIN is short-circuited to ground. Only

a weak pull-up between pins LIN and VBAT is present.

Sleep mode can be activated independently from the actual level on pin LIN, pin TXD or

pin WAKE_N. This guarantees that the lowest power consumption is achievable even in

case of a continuous dominant level on pin LIN or a continuous LOW on pin WAKE_N.

When VBAT drops below the power-on-reset threshold Vth(POR)L, the TJA1021 enters

Sleep mode.

7.3 Standby mode

Standby mode is entered automatically whenever a local or remote wake-up occurs while

the TJA1021 is in Sleep mode. These wake-up events activate pin INH and enable the

slave termination resistor at the pin LIN. As a result of the HIGH condition on pin INH the

voltage regulator and the microcontroller can be activated.

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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