TPS65381 Safety Operation Requirement for WD

Toshio Ushikubo

Hello,

Please advice TPS65381 can satisfy following Safety Operation Requirement from customer.

Please advise if TPS65381 can control NRES for MCU as follows.

Detect Q&A watchdog fail and reset MCU.
Detect Q&A watchdog fail and reset MCU.
If reset count reaches specified number TPS65381 holds NRES=Low.

When watchdog fail condition(WD_FAIL_CNT=7 & WD_RST_EN=1) is satisfied, TPS65381 enter Global Reset Condition and WD reset loop is repeat forever if MCU is still un-responsible to WD requirement. So it may be difficult to satisfy this requirement.

Please advise how to cope with above requirement.

Best Regards.

over 9 years ago

0 Mahmoud Harmouch over 9 years ago

TI__Mastermind 24740 points

I' m not sure if I well understood the question. It seems the Micro is bad and WD fail will continue. In this case the module has to be changed.

0 Toshio Ushikubo over 9 years ago in reply to Mahmoud Harmouch

Mastermind 9620 points

Hello Mahmoud-san,

Thank you for your answer.

When MCU is bad and WD fail will continue ECU must be Safe State( Reset is maintained Low and MCU stops) For functional safety.

So, customer asked me whether TPS65381 can control NRES as I posted before.

Could you please advise whether TPS65381 can control NRES as customer requested.

Best Regards.

0 Mahmoud Harmouch over 9 years ago in reply to Toshio Ushikubo

TI__Mastermind 24740 points

Toshio-san, here is the sequence:

1- MCU failure

2- MCU worm reboot

3- WD time out

4- TPS65381 shuts down

5- Force MCU to cold reboot

0 Toshio Ushikubo over 9 years ago in reply to Mahmoud Harmouch

Mastermind 9620 points

Hello Mahmoud-san,

Thank you for your answer, but It cannot be understood how TPS65381 can satisfy the requirement of customer from your answer. .

-Could you please answer if TPS65381 can satisfy customer's requirement?

-Please explain more detailed sequence using register settings and STATE change with reason.

Best Regards.

0 Toshio Ushikubo over 9 years ago in reply to Toshio Ushikubo

Mastermind 9620 points

Hello Mahmoud-san,

Please answer for my question I posted Jul 10 2014.

Best Regards.

0 Mahmoud Harmouch over 9 years ago in reply to Toshio Ushikubo

TI__Mastermind 24740 points

Requirements #1 and #2 are identical.

All specified requirements can be met

- When WD Fail Count reaches count of 7 (while WD_RST_EN is set to ‘1’) TPS65381 drives NRES low and MCU warm reboot occurs

- MCU ERROR pin monitoring can be used to force system shutdown (and permanent NRES driven low) when persistent MCU failure is observed

When device is in ACTIVE state and MCU ERROR pin monitoring failure is detected device transitions to SAFE state

NOTE: MCU error pin failure is indication of the MCU failure

Every time device enters SAFE state Device Error count is incremented
User has to setup SAFETY_PWD_THR_CFG register for the number of allowed system resets before device transitions to STANDBY state (with NRES driven low)

Note: see diagram (from figure 5-17, Device Controller State Diagram, page 63)

0 Toshio Ushikubo over 9 years ago in reply to Mahmoud Harmouch

Mastermind 9620 points

Hello Mahmoud-san,

Thank you for your answer.

I understand that in case of using MCU ERROR pin monitoring, TPS65381 can drive NRES low permanently after specified reboot times. But WD error cause repeated reboot and can’t drive NRES low permanently.

Thanks and Best Regards.

0 Manoj R over 9 years ago in reply to Toshio Ushikubo

TI__Intellectual 1595 points

Please find the updated version of safety diagnostic library support for the TPS Driver.

http://www.ti.com/tool/safeti_diag_lib
The Product information page is not up to date and will be updated soon.

Please do provide feedback if any on the same.

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TPS65381 Safety Operation Requirement for WD