BQ25570 - latest release details and can the setup be altered to all battery to supply system when not charging

James Hillman

Other Parts Discussed in Thread: BQ25570, BQ24090

Hi everyone,

I have been looking at the energy harvesters to charge low capacity batteries from a DC supply. The BQ25570 looks interesting but my circuit will require more than 1.8V on the load. Is there a way I could adjust the circuit to create something similar to powerpath so the battery powers the load when not charging? I couldn't understand how this, or some of the other devices, would allow the load to operate when not charging. Happy to take recommendations for other devices.

I was interested in knowing when the device will be active.

Thanks,

James

over 12 years ago

0 Jeff F over 12 years ago

TI__Guru**** 166996 points

There is a PMOS FET between the VBAT and VSTOR pins that remains on as long as VBAT > battery undervoltage threshold, internally set to ~2.0V. So, as long as the battery is above 2.0V, VBAT=VSTOR. If the load is attached to VSTOR as recommended, the battery will power the load.

The bq25570 is designed to be powered from a HiZ source, like solar panel, TEG, piezoelectric source. It will operate when powered from a LoZ DC supply but is not optimized for such operation. Perhaps bq24090 family is an option?

0 Joppe Lauriks over 11 years ago in reply to Jeff F

Prodigy 20 points

So if VBAT is > 3.3V and VOUT is set at 3.3V it will stay 3.3V untill VBAT gets below 3.3V?

0 Jeff F over 11 years ago in reply to Joppe Lauriks

TI__Guru**** 166996 points

VOUT is the out of a buck converter that is powered from VSTOR=VBAT. VSTOR=VBAT needs to be slightly greater than VOUT in order for VOUT to rename regulated; otherwise, VOUT = VSTOR - IOUT*RDSON.

0 Joppe Lauriks over 11 years ago in reply to Jeff F

Prodigy 20 points

Wat is the Max/Min Voltage out for VOUT. In the user guide for the evaluation module it states its adjustable between 1.3 - 5.05V. But the value is no where in the data sheet or am I over looking something?

0 Jeff F over 11 years ago in reply to Joppe Lauriks

TI__Guru**** 166996 points

The maximum is 5.5V. The user's guide has a typo.

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BQ25570 - latest release details and can the setup be altered to all battery to supply system when not charging