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BQ25703A: About the operation that HIDRV1 and LODRV2 turn on at the same time

Tsukui Yusuke
Guru 21930 points
Part Number: BQ25703A

Hi,

I am evaluating BQ25703AEVM under the following conditions.
www.tij.co.jp/.../sluubg6.pdf
・VIN=10V
・CELL＿BATPRES：2cell setting
・VSYS＝8.4V setting
・ISYS＝0 to 5mA
・Charge current = 0.2A

In the evaluation, we confirmed the operation that HIDRV1 and LODRV2 turn on at the same time.
I will attach the waveform.
This phenomenon occurs after setting the charge off (set the CHRG_INHIBIT bit).

BQ25703A HIDRV1 and LODRV2 waveform.pdf

Is this a function of the BQ25703A?
Could you give me a detailed view of this behavior?

Best regards,
Yusuke

  • 0
    TI__Mastermind 24075 points

    Hi Yusuke-san,

        In buck mode, Q1 and Q2 will be switching with Q4 always on, and Q3 "off" (on for very brief periods of time). Q4 is an NFET driven by a +VGS through the BTST2 pin, however the BTST2 cap will need to be recharged when the voltage drops (see BTST refresh spec in EC table). For the recharge of BTST2, Q3 will need to turn on briefly for this to happen, as BTST pin is only charged when LSFET is on and HSFET is off.