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Original question:

BQ25600D: BQ25600

BQ25601: BQ25601 output issue without battery

Nithin james
Prodigy 100 points
Part Number: BQ25601

Hi Sir/Madam

We are using BQ25601 PMIC for one of our project ,

we are facing issue while using without battery (only input power is connected)

Output at SYS pin is 1.88 volt when we operated with USB 5V  500 ma Charger ,( battery is not connected). Maximum load is below 500ma

while probing on STAT Pin we are getting 50% duty cycled pulses, which means fault charge conditions. But we are unable to find out where the fault.

when we are connecting battery of 4.2v (Fully charged) same voltage  is getting at SYS pin  image of circuit is attaching for referring.

Requesting you to suggest solution for above issue.  

  • 0
    TI__Expert 5590 points
    Hi James:

    When the battery is removed, the SYS voltage should oscillate between 3.6V to 4.2V because of BAT pin recharge and discharge. You may try to remove your load from SYS. When battery is connected, the SYS voltage will follow BAT voltage if battery voltage is above 3.5V or so.
  • 0 in reply to Hong Mao
    Prodigy 100 points

    Hi Mao,

    Thanks for your reply.

    As per your first point we suppose to get 3.6v to 4.2v at SYS pin without battery .But we are getting only 1.8v ,this is the issue we are facing.

    Kindly suggest solution. 

    We assuming that there is no problem with our schematic. if there please comment that also.

  • 0 in reply to Hong Mao
    Prodigy 100 points
    we assuming that there is no problem with our schematic. if so please suggest the changes required in schematic.
  • 0 in reply to Nithin james
    Prodigy 100 points
    Hi Mao,

    After removing load we are getting 3.6v at system (Without battery). We have doubt why it is not getting 3.6v with load. Is this IC will support loading system without battery.

    Kindly revert back
  • 0 in reply to Nithin james
    TI__Expert 5590 points
    James:

    As I said, if the battery is removed, you will get voltage between 3.6V to 4.2V. Looks like your load is over the current limits of either adaptor or the charger's input current limit. The schematic looks fine, but QON should not be connected to GND if it is not used. When you have 1.8V at SYS, do you see the charger is switching? Do you have switching waveforms at SW? What is VBUS voltage?