bq25895evm-664 eval board setup

Jeffrey Simon

Other Parts Discussed in Thread: BQ25895EVM-664

I have the bq25895evm-664 eval board and want to configure it for autonomous mode for a charging circuit/power management. I have multiple questions:

First, when i increase the voltage on the vbus, the pmid output also increases. How can the PMID output be steady at a 5V no matter if connected to battery vbus?

How can I set the boost enabled without a host?

Basically my needs are 5V input , regulated 5V output on PMID, and when VBUS no longer is supplied voltage, the 3.7V battery kick in and power the PMID 5V out.

Is there a better way to do this?

thank you for any and all assistance.

over 8 years ago

0 Sergio Iannace over 8 years ago

TI__Intellectual 1520 points

Hi Jeffrey,

as the picture below shows (section 8.1 of the datasheet), the PMID pin has to follow the input voltage at the VBUS pin.

This is true for normal charging operation (buck mode) when the output is basically the SYS pin and/or the BAT pin. When the device enters OTG mode (boost mode), the output is at the PMID pin and it is regulated at 5V.

You can enable the Boost mode if the OTG pin is high (and no input source is detected at VBUS).

Regards,

Sergio.

0 Jeffrey Simon over 8 years ago in reply to Sergio Iannace

Prodigy 20 points

Now when the fet is switching there is a 70ms time at which the voltage dips. is there any way to reduce this supply drop to the load?

0 Sergio Iannace over 8 years ago in reply to Jeffrey Simon

TI__Intellectual 1520 points

Are you referring to the VSYS voltage?
To understand the issue it would really help if you can provide:
- mode of operation (buck or boost mode)
- register settings
- what the current and voltage required by the load
- input current and voltage

Thanks,
Sergio

0 Chris Jordan over 7 years ago in reply to Jeffrey Simon

Prodigy 40 points

Hi Jeff, we have a similar problem though the dip to battery voltage only seems to last for 35mS. See posts: 'BQ25895EVM Switchover to OTG mode voltage dip'

Power management

Power management forum

bq25895evm-664 eval board setup