• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 629 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.

BQ24610: Battery detection

Mason Noh
Expert 2490 points
Part Number: BQ24610

Hi TI,

I'm testing with BQ24610EVM for 2cell charging.

I have a question about battery detection.

Sometimes a charger cannot charge after inserting a battery. At this time, STAT1 is blinking every 1.7sec.

The battery was connected while input power was being applied.

Refer to below waveform. CH1: Vbat(SRN), CH3: LODRV 

But this issue is solved when TTC pin to ground. (TTC setting:1-2)

Please let me know the reason. 

I just changed the feedback resistor on the EVM circuit diagram for 2cell. (R25: 909K-->300K)

  • 0
    TI__Mastermind 24075 points

    Hi Mason,

       In these corner cases you are most likely inserting a battery that is near fully charged. When fully charged battery is inserted, STAT1 will be high indicating charge is not in progress, and as battery discharged, eventually the voltage on VFB will satisfy the VRECHG threshold, triggering a recharge cycle during which STAT1 will be low, which is the oscillation that you see. This is with termination enabled, as when VFB and termination current criteria are satisfied, charger will shut off charge current. During charging if you have impedance between your battery and where charger senses battery voltage, then BQ24610 will sense battery voltage + charge current * impedance. When termination is hit, charge current is turned off, so now battery senses battery voltage as opposed to battery voltage + Iterm*impedance, and this voltage drop triggers the VRECHG threshold starting a new charge cycle.

        This is why pulling TTC low solves your issue, as this disables termination of the charger, so battery is continuously being charged at low currents to keep it topped off, and you don't see the loss of the Iterm*impedance voltage drop, and VRECHG threshold is not triggered. You can also try decreasing termination current or looking at setup to decrease impedance (long wires from battery to board, long traces etc)

  • 0 in reply to Kedar Manishankar
    Expert 2490 points

    Hi Kedar,

    I don't understand exactly.

    When fully charged battery is inserted, STAT1 will be high indicating charge is not in progress,

    --> Is it mean charging complete? But at this time STAT2 is high(OFF). Only STAT1 is changing repeatedly every 1.7 seconds.

  • 0 in reply to Mason Noh
    TI__Mastermind 24075 points

    Hi Mason,

        I have a feeling that STAT2 is slow in registering charge complete, so the toggling just seems on STAT1. If you see the SRN signal, the voltage climbs to your charge regulation set point of 8.46V which would be charge complete. Try overlaying STAT1 on the signal you captured above. Show STAT1, VFB close to IC (offset this signal by 2V), charge current and PH. Let me know your termination current setting when you have the results for this test as well.

  • 0 in reply to Kedar Manishankar
    Expert 2490 points

    Hi Kedar,

    I found that the problem was solved through further tests.

    I added a filter cap(2.2pF) between FB and GND.

    Did the problem impact FB due to the noise caused by impedance?

  • 0 in reply to Mason Noh
    TI__Mastermind 24075 points

    Hi Mason,

       It is possible as impedance is what was probably discharging your battery quicker than expected and causing it to cyclically keep hitting recharge threshold.