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BQ32002: Solution for increase of hold-up time

Riley Huang
Prodigy 300 points
Part Number: BQ32002

Hi Team,

My customer are asking for a solution for effectively increasing the hold up time without using supercapacitors (as company policy advises against capacitors with electrolytes) and batteries, are there any other solutions to effectively increase the hold-up time of the RTC backup supply power?

My customers current idea is as follows: placing solid-state capacitors on the 12V side, with a maximum capacitance of 1000uF/2700uF.

But if a hold-up time of several days is required, numerous capacitors would need to be employed.

The customer's target is 30 days,.

Thanks.

  • 0
    TI__Guru* 90560 points

    Hi Riley,

    Did you say, you are not going to use supercap and batteries, but use a big capacitor at the Vback pin?

    Vback current is 1.5µA, assume the initial Vback voltage is 3.3V, so the resistance is 3.3/1.5µ = 2.2MΩ. 

    Vback voltage range is 1.4V to 3.3V. With a 2700µF cap, in approx. 5000s, the voltage will discharge to 1.4V. 

    Even if we use a 0.22F supercap, we can only maintain the operation for 4.8 days.