PF8500 Using with Apalis IMX8 Module

[samet]

Hi,

We'll use the Apalis IMX8 Board. And in front of these module, we supply Apalis IMX8 module with FS8500 SBC. Because our product must be minimum ASIL B level. But When I read the datasheet of FS8500. The PSYNC pin must connect to PMIC PGOOD pin. We can't see the PGOOD pin on module connector's pinout. Is there any problem when I dont connect to the PMIC PGOOD pin.

[reyes]

Hi,

I think you are referring to the PSYNC of the FS8500 SBC and to the PGOOD pin of the external PMIC (PF81), correct?

According to the datasheet, when PSYNC is used to synchronize one FS85/FS84 and one external PMIC, PSYNC pin of FS85/FS84 shall be connected to PGOOD pin of the external PMIC. Which I think is what you are trying to do, however, the Apalis IMX8 Board doesn’t have access to the PF81 PGOOD pin, correct?

Unfortunately, Alpalis IMX8 Board was not designed by NXP, but by a third party, so we did not review their designs. If this board does not include access to PGOOD pin of the PF81 PMIC, it is not possible to connect it to the FS85 PSYNC pin, which will cause that the PF81 PMIC of the Alpalis board and the FS85 SBC will work separately and never synchronize.

Let me try to explains what happens during the startup when using PF81 and FS85 connected together using PSYNC and PGOOD:

In a typical automotive circuit, main BAT is connected to FS85, then…

1)FS85 is starting: VPRE, BOOST starts

2)PF8100 is starting supplied by VPRE of FS85

3)PGOOD from PF8100 is released when ready

4)FS85 detect the PSYNC event and continue its own power sequence.

Then, if PGOOD and PSYNC are not connected, you need to calculate the time it takes for the PF8100 of the Alpalis to fully turn on the board, and after that start with the FS85 power sequence.

Regards,

Jose