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BQ2004H, Not exiting hold-off period in fast charge mode?

Zach Jacobs96065
Prodigy 50 points
Other Parts Discussed in Thread: BQ2004H, BQ2004

I have a BQ2004H chip and it seems to not be exiting the Hold-off period after entering fast charge mode.

Upon startup, the following steps happen:

1)  LED1 stays low and LED2 pulses 1/8s high, 1/8s low for a few seconds.

2)  LED1 stays low and LED2 goes high.

3) Pulse train on MOD pin of 12% duty cycle with 260uS high.

Table 1 indicates the hold of period should be 273 seconds but I have let the chip run for about 30 minutes and MOD is still behaving as seen in step 3 above.  Does anyone know why this seems to be stuck in the hold-off period?  How is the safety time used?  Does this stop fast-charge after 650 minutes?

With relevant values:

TM1, TM2 = Vss

temp:

TS = 1.92V

VLTF = 2v

VHTF =1.46V

VTCO = 1.19V

batt voltages:

Vmcv = 4v

Vedv = 2v

Vbat = 2.475v

Vsns = Vss

  • 0
    TI__Mastermind 31220 points

    Hi Zach,

     The safety timer depends on the rate of charge and the status of TM1 and TM2. In your case TM1 and 2 are both high, if the corresponding rate of charge is 2C then 39 minutes is the safety time. What is the status of VDSEL?

    Can you please send me some wave forms to look at? Make sure the temperature sensor is not causing the issue and also please double check your schematic with the EVM.

     -Tahar

  • 0 in reply to Tahar Allag
    TI__Mastermind 31220 points

    Zach

    Any updates or more info regarding this issue...

    -Tahar

  • 0 in reply to Tahar Allag
    Prodigy 50 points

    Hi Tahar,


    Sorry I have been busy debugging lately.  I replaced the BQ2004H with a BQ2004 and that fixed the issue of never exiting the hold-off period since the BQ2004 doesn't have a hold-off mode before fast-charge.  I am using this to drive a LT1618 constant current dc/dc converter and have been trying to debug noise issues since the original post.  If I run into anymore issues, I will report back.  So far, the BQ2004 chip seems to be working as expected.

    Thanks for the follow-up.

    --Zach

  • 0 in reply to Zach Jacobs96065
    Prodigy 50 points

    and by the way, Vss = GND so TM1 and TM2 were tied to GND.

  • 0 in reply to Zach Jacobs96065
    TI__Mastermind 31220 points

    VSS is System ground. If you connect TMR1&2 to VSS, sure they will be grounded to system ground.