BQ24650: BQ24650 not charging

Hi Jan,

   Scope capture 2 shows BQ24650 undergoing battery absent detection, which is correct operation when no battery is connected. R2 and R1 set charge regulation voltage according to 2.1*(1+R2/R1) so witth R2 = 499k and R1 = 100k which would give a charge regulation voltage of 12.58V. The battery you are connecting is 13.6V so this would result in BAT OVP. 

Hello Kedar,

thank you for your message. Schema was taken from reference design with default values, our values I wrote bellow picture.

Our R1 = 16.9kOhm, R2 = 97.6kOhm, so it will be: 2.1 * (1 + R2/R1) = 2,1 * (1 + 97.6/16.9) = 14.22V.

Our current voltage level of battery is 13.6V, but still doesn't charging. Do you want send our scheme?

Thank you,

Jan

Hi Jan,

    Yes I can take a look at the schematic.

Hello Kedar,

thank you, I just sent you our schematic. Please for your review, if is everyting ok.

Thank you,

Jan

I would like to ask you for review.

Thank you,

Jan

Hi Jan,

    Looking at the schematic you have here, you have R34 = 1k, and R35 = 5.86k. From above schematic you have the resistors swapped (Right now your charge regulation would be set for 2.46V). If R35 = 1k, and R34 = 5.86k, then yes you will have a charge regulation voltage of 14.406V. You can review section 8.3.1 Battery Voltage Regulation of the BQ24650 datasheet for the formula.

Hello Kedar,

sorry, I overlooked this. It was old schematic. Here is current schema with R35 = 16.9kOhm, R34 = 97.6kOhm

Current schematic:

Thank you,

Jan

Hello,

for debug propose, we build new PCB without other circuits and we got following behavior:

Picture 1 - Vout without inserted battery 

Picture 2 - SRN Voltage after input turn on. Vout voltage after output diode is constantly on battery voltage level.

Currently measured values with battery:

Vreg = 5.93

VCC = 23V

Vref= 1.94V

TS = 3.29V

MPPset= 1.52V

RSN = 0.85V

Thank you,

Jan