TJA1080ATSSLASH2SLASHT datasheet(22/49 Pages) NXP

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TJA1080A

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Product data sheet

Rev. 5 — 24 February 2011

22 of 49

NXP Semiconductors

TJA1080A

FlexRay transceiver

6.6 Fail silent behavior

In order to be fail silent, undervoltage detection and a reset mechanism for the digital state

machine is implemented.

If an undervoltage is detected on pins VCC, VIO and/or VBAT, the transceiver will enter a

low power mode. This ensures a passive and defined behavior of the transmitter and

receiver in case of an undervoltage detection.

In the region between the minimum operating voltage and the undervoltage detection

threshold, the principle function of the transmitter and receiver is maintained. However, in

this region parameters (e.g. thresholds and delays of the transmitter and receiver) may

deviate from the range specified for the operating range.

The digital state machine is supplied by VCC, VIO or VBAT, depending on which voltage is

available. Therefore, the digital state machine will be properly supplied as long as the

voltage on pin VCC or pin VIO remains above 4.75 V or the voltage on pin VBAT remains

above 6.5 V.

If the voltage on all pins VCC, VIO and VBAT breaks down, a reset signal will be given to the

digital state machine as soon as the internal supply voltage for the digital state machine is

not sufficient for proper operation of the state machine. This ensures a passive and

defined behavior of the digital state machine in case of an overall supply voltage

breakdown.

6.6.1 VBAT undervoltage

• Node configuration: If the UVVBAT flag is set the transceiver will enter Sleep mode

(pins INH1 and INH2 are switched off) regardless of the voltage present on pins EN

and STBN. If the undervoltage recovers the wake flag will be set and the transceiver

will enter the mode determined by the voltages on pins EN and STBN.

• Star configuration: The TJA1080A in star configuration is able to transmit and receive

data as long as VCC and VIO are within their operating ranges, regardless of the

undervoltage on VBAT.

6.6.2 VCC undervoltage

• Node configuration: If the UVVCC flag is set the transceiver will enter the Standby

mode (pin INH2 is switched off) regardless of the voltage present on pins EN and

STBN. If the undervoltage recovers or the wake flag is set mode switching via pins EN

and STBN is possible.

• Star configuration: If the UVVCC flag is set the transceiver will enter the Star-sleep

mode.

6.6.3 VIO undervoltage

• Node configuration: If the voltage on pin VIO is lower than Vuvd(VIO) (even if the UVVIO

flag is reset) pins EN, STBN, TXD and BGE are set LOW (internally) and pin TXEN is

set HIGH (internally). If the UVVIO flag is set the transceiver will enter Sleep mode

(pins INH1 and INH2 are switched off). If the undervoltage recovers or the wake flag is

set, mode switching via pins EN and STBN is possible.

TJA1080ATS/2/T Datasheet(PDF) 22 Page - NXP Semiconductors

TJA1080ATS/2/T Datasheet(HTML) 22 Page - NXP Semiconductors

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