(EDIT: I meant to post this to the projects, designs and technical stuff board - could someone move it please? Thanks!)
Hi guys,
I've been hacking my
Sinclair C5 a bit lately, and at the moment I'm trying to design a control/protection circuit for the battery pack. The main chip on it is going to be a TI bq76920. It looks like a great chip which does most of the things I want to do, but I have one problem with the datasheet.
On page 43 of the
datasheet, it shows a configuration with two anti-series MOSFET to open and close the pack output. What confuses me though is that it's possible to have CHG on and DSG off or vice versa. This means current can flow in one direction through one of the FETs but has to go through the body diode of the other. That body diode would then get very hot. It seems to me that the more sensible way to do it would be to have them both switched together, so they're either both blocking or both conducting.
Does anyone know what they're trying to do here? I'm tempted to just AND up the CHG and DSC pins so that they're always in the same state.
Thanks
Alec