BQ24075T: About BAT pins when VIN=0V

Yuta Nishie

Part Number: BQ24075T

Hi,

What is the recommended operating voltage range that can be input to the BAT pin when VIN=0V?

How does Vout operate when the input voltage of the BAT pin falls below min of the recommended operating voltage range? Does Vout=0V?

Best Regards,

Nishie

7 months ago

+1 Rafael Camarillo 7 months ago

TI__Intellectual 910 points

Hello Nishie

Thanks for reaching out on E2E. In regard to the physical aspect of the IC, the absolute Maximum Rating for the VBAT pin is -0.3V to 5V.

If you look at the simplified circuit on the first page of the d/s, for the BAT pin and the OUT pin. There is an NMOS FET that is connected from the BAT pin to the OUT pin. VOUT will be (VBAT - Voltage Drop of BATFET). Please be aware, there must be enough input power to cover the load on OUT.

V/R

Rafael Camarillo

0 Yuta Nishie 7 months ago in reply to Rafael Camarillo

Genius 3200 points

Hi Rafael-san,

Thank you for your reply.

I looked at the data sheet 9.3.1 Undervoltage Lockout (UVLO).

When VIN=0V, VSYS=Low, does the NMOS FET (Q2) always stay on regardless of the VBAT value? I would like to know if it turns off when it is between -0.3V and 5V, which is within the absolute maximum rating range.

Best Regards,

Nishie

+1 Rafael Camarillo 7 months ago in reply to Yuta Nishie

TI__Intellectual 910 points

Hello Nishie,

Yes in that case the NMOS would be on to supply power from the battery. For Q2 to be on then VBAT would have to be >0.4V. Then you would see voltage on VSYS.

V/R

Rafael Camarillo

Power management

Power management forum

BQ24075T: About BAT pins when VIN=0V