Why does UJA1169 output 2.8V and 0.5V

[Baikian]

I am using the UJA1169 as the power supply chip for the S32K311. To test its functionality, I repeatedly perform sleep -> wake-up operations on the UJA1169.

However, during this process, the UJA1169 occasionally enters a strange operating mode: V1 outputs 2.8V, and V2 outputs 0.5V. At this time, the S32K311 does not receive power and cannot function properly. Even cycling the power on the UJA1169 does not restore normal operation. It can sometimes be recovered by forcing the SBC into Forced Normal Mode, but this method does not always work.

Could you explain the reason for this? Does the UJA1169 have a specific mode where it only outputs 2.8V and 0.5V, while the RSTN remains in a low-level state?

Thanks

[JozefKozon]

Dear Baikian,

first please note, that for the S32K3 a recommended SBC is FS26 or FS23. Please refer to this link. I would recommend you to use FS26, because there is even an application note AN13323. 

If you want to stick with the UJA1169, please confirm the full UJA1169 part number. 

Please note, we also have newer UJA1169A. Please confirm if you are not using this one. 

Please share your schematic with voltage levels and part values.

With Best Regards,

Jozef

[Baikian]

I use UJA1169ATK/X

When repeatedly resetting, it is possible that the S32K is affecting the SBC, because after removing the SBC, there is still voltage coming from the S32K, and even after power cycling, it cannot be restored.

[JozefKozon]

Dear Baikian,

thank you for the information. Please share your schematic with voltage levels and part values.

Regarding the UJA1169A using with S32K3, this wasn't tested by our application team. I would still recommend you to change the SBC for the recommended ones, which were tailored and tested to be used with the S32K3.

With Best Regards,

Jozef