Supercap backup using the TPS65217C?

Andrew Perkins is Cool

Other Parts Discussed in Thread: AM3358

I am considering using a supercap on the battery charging circuit, but understand that it will appear as a shorted output. Will this work? What I want is a way to provide uninterruptible power to a 5VDC powered digital system, based on the AM3358.

The main idea being to initiate a power fail mode, where filesystems are put into a stable state before power disappears completely. I want to prevent database corruption at the sudden loss of DC power and need a backup to do so. It only needs to work for a short time, but needs to charge quickly.

I am using the TPS65217C. Would a small battery be a better choice?

over 9 years ago

0 Richard Solarski over 9 years ago

TI__Genius 10885 points

Hi Andrew,

Why do you say it would appear as a short? The PMIC will supply ~7.5mA to the BAT pin until BAT_SENSE reaches ~1.5V. Can your cap reach 1.5V at this current before a valid power-fail condition?

0 Andrew Perkins is Cool over 9 years ago in reply to Richard Solarski

Prodigy 100 points

Thanks for the confirmation. That is what I meant when I said it would be treated as a shorted battery < 1.5V. I know this is for cell conditioning, but it will take a while to charge a 10F capacitor with that current, until it is 1.5V. I may have to trick the sense in some way, such as clamping it at 3.3V, in order to get a higher current of say 500mA. Is that possible?

0 Richard Solarski over 9 years ago in reply to Andrew Perkins is Cool

TI__Genius 10885 points

Hi Andrew,

It is possible to trick the charging scheme by adjusting the voltage on the BAT_SENSE pin, so the current sourced to the cap will depend on how the charging profile is configured.

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Supercap backup using the TPS65217C?