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TPS63001: TPS63001

Sudhir Gupta
Intellectual 285 points
Part Number: TPS63001

I am designing a circuit with input being supplied by a 3.7 V (nominal) Li-Ion battery and the output is fixed 3.3 V. Majority of time, the input voltage will be greater than 3.3 V but as the battery drains the input voltage may drop to 3 V.  There is also a battery switch that can disconnect the battery from the circuit. Under these conditions, is it possible to eliminate RC circuit between Vin and VINA and have VINA pin directly connected to Vin pin?

I will appreciate clarification on the reason for the RC filter. It appears that with this RC circuit in place, when the battery is switched on the voltage on VINA pin will rise slowly, but when switching off VINA pin will have the full battery voltage, where as Vin pin will have 0 voltage, which will rise slowly by capacitor through the resistor (of RC circuit) and eventually dropping back to zero, as capacitor discharges. 

Kind Regards,

Sudhir Gupta

  • 0
    TI__Mastermind 21565 points

    Hi Sudhir:

    Thanks for asking. 

    For your application, the Vin will be larger than Vo some time. So the converter would operate in Buck mode sometime. For a Buck, the input side has high dI/dT. There will be significant voltage ripple caused by ESL, ESR in the route or battery. (Even the battery and Cin can reduce some of them)  

    The RC filter is to make the control supply clean and stable. If you connect it to Vin directly, I afraid it will be coupled with such ripple. So we still recommend add the RC filter.  

    You can modify the RC time Constance to meet the delay requirements.

  • 0 in reply to Minqiu Xie
    TI__Mastermind 21565 points

    Hi Sudhir:

    As long time no hear from you, I assume you have solved the issue. If not, just reply below. Thank you!