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bq24193 - IC failing under high current loads

Laura Knight
Prodigy 40 points
Other Parts Discussed in Thread: BQ24193

We are seeing large fallout of bq24193 ICs during DVT when running max loads.

Setup:

Bench power supply set to 14.0V input, 3.0A limit.

bq24193 VBUS measured at 14.0V, 1.16A. (ILIM set in SW to 3.0A. External ILIM resistor 0 Ohms).

- IC is fast charging battery simulator at 4.0V, 0.54A. Battery simulator will continuously sink current.

- SYS output 4.1V with max load attached.

Tests runs successfully (4-16 hour test). Device is powered off and sits overnight. In the morning, the bq24193 emits a buzzing noise and discharges 2A into the battery simulator. If battery is disconnected, SYS output voltage is 4.0V and has 0.5V of ripple.

Replacing bq24193 resolves issue.

It is unknown how or why the bq24193 IC is breaking.

  • 0
    TI__Expert 4285 points

    Hi Laura,

    I'd like to know some more details of your test condition.

    1. what's your load (in A) at SYS? Your input was 14V x 1.16A, close to 14W. your output is BAT + SYS.

    2. When you rebooted next day, what's your power up sequence? for example, in what order VBUS, VSYS, VBAT was turned on and with what settings in current and voltage?

    3. Is this failure mode repeatable?

    Best Regards,

    Linhong

  • 0 in reply to Linhong Qin
    Prodigy 40 points
    1. I believe our peak current is the culprit. We measured SYS supply after external inductor and capacitor 4.15V @ 5.46A (peak) and we are also fast-charging a battery simulator 4.0V @ 0.57A.

    2. We power up VBUS first, then enable VBAT.

    3. Yes, we have gone through 4 ICs (and counting). I was only measuring our average VBUS input power before, but our output current is way above the 4.5A specification.
  • 0 in reply to Laura Knight
    TI__Expert 4285 points

    Hi Laura,

    Can you capture the waveform of inductor current and battery current? 5.46A seems high. But our IC should provide cycle-by-cycle protection.

    Also, can you describe in detail how the failure could be reproduced?  Did all 4 ICs fail at restart after a run in previous day, or some failed during run? Was the SYS load always on? Is your restart setup/procedure the same as your initial startup?

    Regards,

    Linhong

  • 0 in reply to Linhong Qin
    Prodigy 40 points
    Hi Linhong,

    Unfortunately (although expected), the IC was broken this morning from my current measurements yesterday. We will have to swap the IC.

    The failure always occurs after the unit has been sitting powered off, typically overnight. This morning I only powered the unit up with 14V supply to VBUS. There was no battery connected and the load was typical ~0.4A. As soon as I powered the unit on I knew it was a bad IC because I could hear the audible buzzing which indicates a lot of ripple on SYS output. The registers all read 0x20. The system does power up with VBUS for a few minutes, but will start rebooting and eventually shutoff.

    I can alternatively start-up our device with VBUS and then turn-off the input power supply to allow the system to be powered via the battery. This works ok and I can read the registers (all are default and 08=0x00, 09=0x80). I assume our registers are not getting written when we power-up because something about VBUS is now broken.

    It is odd that if we are overstressing the chip, there are no faults or protections. What is cycle-by-cycle protection? Is there a fault that will indicate if the output is over-current?

    Regards,
    Laura
  • 0 in reply to Linhong Qin
    Prodigy 40 points
    Also, how do I provide attachments?
  • 0 in reply to Laura Knight
    TI__Intellectual 1910 points
    Laura,
    Can you contact me by email for best time to have a conference call? My email is s-wong@ti.com . It would help tp speed up the closure with a call.
    Regards,Sam