BQ77915: BMS not turning on

Muki

Part Number: BQ77915

Tool/software:

Hey Guys,

I've used the BQ7791514 IC before to make a 4S BMS but my new design isn't turning on. I've tested multiple boards and I tried charging the pack too.

I'm attaching the new schematic - Test Board Schematic

1. The only mistake i seem to have made is populating the BMS with 10M resistor for R14 instead of 1M. could that be causing the problem ?

2. I removed the NTC sensor in the new design. As per the documents, I left the TS pin floating and tied the VTB pin with a 10K resistor to GND

could you pls look into this and let me know what i can do

Thanks & Regards,

Muki

10 months ago

+1 Luis H. S. 9 months ago

TI__Mastermind 42060 points

Hello Muki,

TS should not be left floating, if unused you should have a 10kOhm connecting it to Vss, with VTB connected to it as well.

Best Regards,

Luis Hernandez Salomon

0 Muki 9 months ago in reply to Luis H. S.

Prodigy 220 points

Hey Luis,

Thank you for the clarification

1. Will go ahead and short VTB to TS

2. Can R14 be left at 10MOhm (or) be changed to 1MOhm ?

P.S. I followed the instructions from this E2E post to eliminate NTC - BQ77915 - Temperature Protection

can you leave a note there so that others don't make the same mistake ?

I checked my board. I've connected TS to 10KOhm and tied it ground but left VTB floating. Will short VTB and TS

Thanks & Kind Regards,

Muki

+1 Luis H. S. 9 months ago in reply to Muki

TI__Mastermind 42060 points

Hello Muki,

Muki said:
1. Will go ahead and short VTB to TS

For VTB, you should connect to TS through a 10kOhm as well.

Muki said:
2. Can R14 be left at 10MOhm (or) be changed to 1MOhm ?

I believe it should be fine to leave as 10MOhm. But I would suggest to make 1MOhm to match our EVM.

Muki said:
can you leave a note there so that others don't make the same mistake ?

I will do so.

Best Regards,

Luis Hernandez Salomon

0 Muki 9 months ago in reply to Luis H. S.

Prodigy 220 points

Hey Luis,

I made the changes

I don't know if its visible, I added a tiny 10kOhm resistor between the VTB and TS pins. The BMS is working now

Thank you for your help

Regards,

Muki

+1 Luis H. S. 9 months ago in reply to Muki

TI__Mastermind 42060 points

Hello Muki,

Good to hear .

Best of luck with the rest of your design!

Best Regards,

Luis Hernandez Salomon

0 Usha K 9 months ago in reply to Luis H. S.

Prodigy 61 points

For more circuit feasibility you can create a voltage divider circuit across CCFG Pin so that you can have different cell configuration and test in the same board

Power management

Power management forum

BQ77915: BMS not turning on