Other Parts Discussed in Thread: BQ25756
Tool/software:
Hi,
i am developing a new design with the BQ25820. i have the EVK and the performance looks good. i am not using input current sensing or Vsys out just a stand alone charger. i have my own PCB now. 14V battery charging at around 4A. Have used the BQ25756 Buck-Boost Battery Charger Design Calculator to help with part selections.
i am seeing very poor switching signals and also have managed to damage one IC with REGN dying to 0V. Replaced IC.
Clearly the chip is trying to regulate as i can see switching on HIDRV1 and SW1 and LODRV1. the switching signals do not look clean. i am certain i am missing something in the schematic but cannot find it.
TS voltage is 2.98V with REGN 5.0V so within the charge window. Vin 17V
putting a flat battery it does not start to charge, connecting a partially charged battery killed REGN!
i am certain i have missed some thing, probably very obvious but i cannot see where i have gone wrong, a second pair of eyes would help.
Any comments greatly appreciated.
Mark