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TPS22948: Control load switch from 0.8hz open drain signal

zunuran nasrullah
Prodigy 150 points
Part Number: TPS22948

Tool/software:

We are working on a wearable device project where we we are using wireless charging system. Wireless receiver IC is LTC4124. Now We want to control this TPS22948 load switch from this CHRG status Pin. Without using MCU. Now real issue is this CHRG pin has 4 possible states. I want that when LTC4124 receives power from transmitter then load switch should disconnect the load so that whole transmitter current is used to charge battery. And as soon as charging is done or transmitter is removed then load switch turns on the load so that battery can provide power to load. But i dont know how this CHRG pin can be utilized to control TPS22948. 

Because when charging starts then it blinks at 0.8Hz. Will this signal good enough to disconnect load switch? End of charge will make this pin pull down so i guess this state is easy to control. 

Or i have to add some external circuit to control load switch from these CHRG pin states?

  • 0
    TI__Mastermind 22300 points

    Hi!

    Yes, you will have to use some external circuit to control the load switch. ON pin will need constant signal and this blink type input won't be reliable. 

    Best Regards,
    Arush

  • 0 in reply to Arush Gupta
    Prodigy 150 points

    Thanks for your reply. Can you suggest what sort of External circuit can be used that can convert this low frequency signal to continuous signal?

  • 0 in reply to zunuran nasrullah
    TI__Mastermind 22300 points

    Hi! You can use a clock and counter or something similar. I am no expert in that domain so I don't think I will be able to tell you the best solution.

    Another solution can be use a cap with this charge signa such that fast blinking signa do not go below certain threshold but slow blinking one goes below the threshold. This won't be a good solution but is one possibility.

    I hope this helps. Please feel free to share with me the final solution which you go with. Also can you tell me more about the end application. I am curious. 

    Best Regards,
    Arush