tja1021 NXP Semiconductors, tja1021 Datasheet - Page 8

• Manufacturer Part Number: tja1021
• Description: Tja1021 Lin 2.0/sae J2602 Transceiver
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TJA1021_3
Product data sheet
7.10 Fail-safe features
7.8 Wake-up source recognition
7.9 TXD dominant time-out function
The TJA1021 can distinguish between a local wake-up request on pin WAKE_N and a
remote wake-up request via a dominant bus state. The wake-up source flag is set in case
the wake-up request was a local one. The wake-up source can be read on pin TXD in the
standby mode. If an external pull-up resistor on pin TXD to the power supply voltage of the
microcontroller has been added, a HIGH level indicates a remote wake-up request (weak
pull-down at pin TXD) and a LOW level indicates a local wake-up request (strong
pull-down at pin TXD; much stronger than the external pull-up resistor).
The wake-up request flag (signalled on pin RXD) as well as the wake-up source flag
(signalled on pin TXD) are reset immediately after the microcontroller sets pin SLP_N
HIGH.
A TXD dominant time-out timer circuit prevents the bus line from 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
internal timer value (t
recessive state. The timer is reset by a positive edge on pin TXD.
Pin TXD provides a pull-down to GND in order to force a predefined level on input pin TXD
in case the pin TXD is unsupplied.
Pin SLP_N provides a pull-down to GND in order to force the transceiver into sleep mode
in case the pin SLP_N is unsupplied.
Pin RXD is set floating in case of lost power supply on pin V
The current of the transmitter output stage is limited in order to protect the transmitter
against short circuit to pins V
A loss of power (pins V
microcontroller. There are no reverse currents from the bus. The LIN transceiver can be
disconnected from the power supply without influencing the LIN bus.
The output driver at pin LIN is protected against overtemperature conditions. If the
junction temperature exceeds the shutdown junction temperature T
protection circuit disables the output driver. The driver is enabled again when the junction
temperature has dropped below T
If V
enabled again when V
BAT
drops below V
to(dom)TXD
th(VBATL)L
BAT
Rev. 03 — 8 October 2007
BAT
> V
and GND) has no impact on the bus line and the
BAT
th(VBATL)H
, a protection circuit disables the output driver. The driver is
), the transmitter is disabled, driving the bus line into a
or GND.
j(sd)
and a recessive level is present at pin TXD.
and a recessive level is present at pin TXD.
LIN 2.0/SAE J2602 transceiver
BAT
.
j(sd)
, the thermal
© NXP B.V. 2007. All rights reserved.
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