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Output Voltage of BQ24075

Apurwa
Intellectual 270 points
Other Parts Discussed in Thread: BQ24075

Hi,

In BQ24075, when VIN is below VBAT + VIN(DT), Q1 FET connected between IN and OUT pins is off, CHG/ and PGOOD/ are high. Q2 FET that connects BAT to OUT is ON.

So Vout for the systems will be 3.7V if we are using a Li Ion battery. (Supplement Mode)

As per the datasheet, Vin> VOUT +VDO, the VOUT(reg) is 5.5V and VBAT(reg) is 4.2V. (Normal Mode)

When Vin is less than VOUT  but greater than VBAT, how will the output of the system vary (DPPM Mode) ?

Vout will  be clamped at 4.3 V ?

And any input voltage below 4.3V will shift it to supplement mode, if not then how will it vary?

Regards, 
Apurwa

  • 0
    TI__Expert 7730 points

    When the input is below 5.5V which is the regulated output voltage, the chip will be in dropout mode. The Vout will track Vin with a voltage drop of Iout* Ron (~300 mohm) and will not clamp at 4.3V.

    The supplement mode only happens when both VIN and VOUT is below VBAT. For example, when VIN = 3.6V, VBAT=3.9V, the VOUT will then be supplemented by VBAT and be very close to 3.9V.

    Thanks,

    Wenjia

  • 0 in reply to Wenjia Liu
    Intellectual 270 points
    Hi Wenjia,
    Thanks for the support.
    I have one more query.
    My input is 4.45v / 2A and as the datasheet suggests Iin Max=1.6A.
    Will it lead to burnout of the IC ?

    Apurwa
  • 0 in reply to Apurwa
    TI__Expert 7730 points
    There's some tolerance at the ILIM, however, whatever is spec'd in the datasheet is the guaranteed operating range. It will not necessarily cause burnout of the IC but it may lead to thermal issue and slow damage to the internal FET. Please use the IC as recommended in the datasheet.

    Thanks,
    Wenjia