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BQ24075T: About BAT pins when VIN=0V

Yuta Nishie
Genius 3200 points
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

  • +1
    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 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 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