BQ76952: REG18 = 0V

Hey Mohammed,

Do you have a schematic I can look at?

The REG18 LDO should power on when the device is taken out of shutdown mode.

Thanks,
Caleb

Here is the schematic, reg18 = 0V, when I press the wake switch it goes to 1.8 V and when I release it goes to 0V.

This is so strange, never happened to me before.

I also tried changing the IC, the problem still persists

Hi Mohammed,

Is this only happening on one board or is it occurring on multiple boards? Is there a chance that switch S2 is stuck? If the RST_SHUT pin is held high, it can put the device back into Shutdown. Can you measure TP1 and the RST_SHUT pin while pushing the wake switch?

Regards,

Matt

this is happening in only one board, I already removed the reset switch, also changed the IC and see it the problem still persists and unfortunately the problem is still there. when I press the wake switch I am getting 1.8V though, once I release it, it goes away

wake switch not pushed

TP1 Bat voltage is 60 V (very strange, actual battery voltage is 57V)

REG18 =0 V

Wake switch pushed

TP1 Bat voltage is 57 V 

REG18 =1.8 V;

This is really strange. Is there a charger connected to you board? It seems that something is shorted or damaged on this board. Can you measure these points in both states:

When REG18=0V, measure TP1, CP1 pin, RST_SHUT pin, CHG, DSG.

Same measurements when REG18 = 1.8V

I did see in the schematic there is no series resistor on the CHG and DSG pins which can result in very fast switching of the FETs - this can damage the FETs or the IC because it will generate high transients. There are good examples of using multiple FETs in parallel in this app report: https://www.ti.com/lit/an/sluaa09a/sluaa09a.pdf 

Best regards,

Matt