BQ76920: SRN vs Vss

Jeffrey Wright

Part Number: BQ76920

Hello;

Just out of curiosity, my client is questioning how the 76920 can measure a negative voltage on its SRN pin, while its VSS is GND. The datasheet explicitly lists the current sense input range of +/- 200mV, but there's confusion as to how this is done by the 920. Any explanation would help assuage my client's concerns ;-D

Thanks!

over 6 years ago

0 Matt Sunna over 6 years ago

TI__Guru* 81035 points

Hi Jeffrey,

This thread might be helpful: https://e2e.ti.com/support/power-management/f/196/t/575178

If it's not enough, let me know and I can try to get a clearer explanation.

best regards,

Matt

0 Jeffrey Wright over 6 years ago

Expert 2875 points

Thanks Matt; Yes, if you could provide information of just how the 920 can measure a negative voltage on its SRN pin during a charge, but has no negative rail, only GND. I "assume" the 920 includes an internal negative voltage generator (like switched cap?) to allow this.

Thanks!

0 Matt Sunna over 6 years ago in reply to Jeffrey Wright

TI__Guru* 81035 points

Hi Jeffrey,

That's right, it uses a switched capacitor integrating delta sigma ADC. The reason it is limited in the negative direction more than the positive is due to the ESD protection diode.

Best regards,

Matt

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BQ76920: SRN vs Vss