• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 961 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

BQ21040: Question about TTDM mode

BQ21040: Issue: /CHG doesn't goes low when battery insert

chentsu chung
Mastermind 6180 points
Part Number: BQ21040

Hi TI,

Thanks for your previous response.

Now I know /CHG will goes low when battey insert even in TTDM mode.

In our device, /CHG doesn't goes low when battery insert.

1. If AC is present, /CHG doesn't goes low when battery insert

2. If insert battery first then insert AC, /CHG goes low

  • 0
    TI__Guru* 75656 points
    Have you tested with the Ti EVM?
  • 0 in reply to Bill Johns
    Mastermind 6180 points

    Hi Bill,

    Customer has no EVM for testing by now. And we have to add a resister from Ts to GND, then can get /CHG high to low while battery insert.

    But sometimes /CHG still stay low when battery remove, we have to touch it by probe then /CHG goes high.

    Here's the question:

    1. Why we have to add resister from Ts to GND, then can get /CHG high to low while battery insert?

    2. Why keep TS floating, /CHG still keep high when battery insert

    3. Why we add a resister from Ts to GND, sometimes /CHG keep low while battery remove (if we touch the pin with probe, then it goes high)

    BTW, here's the schematic for your reference.

  • 0 in reply to chentsu chung
    TI__Guru* 75656 points
    Hello

    1. Why we have to add resister from Ts to GND, then can get /CHG high to low while battery insert?--Bill J - is this a 237k resistor to disable TTDM mode or 10k resistor to simulate NTC?

    2. Why keep TS floating, /CHG still keep high when battery insert--Bill J - This would be TTDM mode. In this mode does /CHG go low if battery is inserted then (V-in ) AC is cycled?

    3. Why we add a resister from Ts to GND, sometimes /CHG keep low while battery remove (if we touch the pin with probe, then it goes high)--Bill J - The CHG pin is an output should not control an features of the device. Can you describe this probe? If a small capacitor is added near the device on CHG pin, .01uf does this stop this behavior?