BQ24650EVM-639: BQ24650EVM-639

Hi Krishan,

   If MPPSET voltage is detected at 1.2V, then this means charger is in input voltage regulation loop, where it will reduce charge current to maintain input voltage. BQ24650 employs battery absent detection, and should detect battery insertion.

When battery is inserted, please capture VCC, SRN, PH and charge current on same scope capture.

Observations:

No Load = DC out stable 

On Load = Output Start fluctuating between ON to OFF.

Screenshot cant be taken

Hi Krishan,

   Scope capture will show us the transition event on battery insertion and will give insight into 

1. If battery detection is working
2. What happens on battery insertion

as well as if there are any other possible loops active.

Nothing in the schematic stands out to me as the issue right now.

hello sir,

        please see the scope capture pic of VCC,SRNand ,PH

      Green line -VCC(12V)

     Pink Line-SRN

      Blue Line-PH

First caputre(without battery)

2nd and third capture(after battery insertion)

3rd capture

we have three channel scope.so can not capture cuurent

Hi Krishan,

  The charger operates in non-synchronous mode when the SRP-SRN voltage is below 5 mV (0.5-A inductor current for a 10-mΩ sense resistor). In addition, the charger is forced into non-synchronous mode when battery voltage is lower than 2 V or when the average SRP-SRN voltage is lower than 1.25 mV..

From your scope capture on 2 and 3 after battery is inserted, the PH node is ringning when both FET have been turned off, as average inductor current is less then 0.25A (5mV threshold, across your 20mohm sense resistor)

For scope capture 1, please re-take with 200ms or 500ms scale. Looking at PH node with small time scale will not tell us if battery absent detection is being implemented or not. At larger time scale, we can see if the internal sink and source currents are correctly attempting battery absent detection.