BQ25504: Trouble chargin Vstor capacitor

Julia Nueno

Other Parts Discussed in Thread: BQ25504

Hello,
I am using BQ25504 with an input of 0,88V and 0,4mA.
However Chvr input capacitor limits input voltage to 330mV. I supposed this was done in order to charge Vstor capacitor using cold start, however the capacitor charges very slowly until it reaches 330mV and then it discharges. The UV_voltage and OV_voltage are in correct range according to the datasheet. Is it normal to limit the input voltage in such way?

Thanks in advance!!

over 9 years ago

0 Jeff F over 9 years ago

TI__Guru**** 165886 points

Yes, the cold start circuit clamps the input voltage to ~330mV until VSTOR is charged to ~1.8V.

0 Julia Nueno over 9 years ago in reply to Jeff F

Prodigy 20 points

Thanks! But then, is it normal it takes so long to charge the vstor capacitor? I think it might be because I've checked output current and it has a value of 0.2uA, it makes sense that it would take very long, right?

0 Jeff F over 9 years ago in reply to Julia Nueno

TI__Guru**** 165886 points

Output current will be in pulses so may be hard to measure accurately. If you are measuring accurately then use I = C*dv/dt and solve for dt.

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BQ25504: Trouble chargin Vstor capacitor