I'm using TPS61023 + BQ24075 in a power management circuit so that when a USB cable is plugged in the system will charge a LiPo battery while still powering the system with 3.3V.

When the USB cable is removed, the system will use the battery as the power source. This switching is done by the BQ24075 whose output voltage is dependent on the input voltage, it means, not regulated.

I'm using a TPS61023, which is a boost converter, to make sure that my output voltage will always be 3.3V regardless of the input voltage. However, that's not what's happening. When I plug in the USB (5V,)the output voltage from the TPS61023 is also next to this voltage. When I remove the USB, the output voltage from TPS61023 is really close to the desired voltage.

Should this behave this way? I thought the TPS61023 would regulate its output regardless of the input voltage and based on the selected resistors on the FB pin.

My circuit is as shown below.

Am I doing something wrong?

The L1 is 1 uH

enter image description here enter image description here

  • 2
    \$\begingroup\$ Unless TPS61023 has output disconnect built in or you pull POWER_CTRL high, you should expect a boost converter to provide output voltage >= input voltage at all times. \$\endgroup\$ – winny Jun 14 at 12:43

Okay, I think I got the answer, directly from the datasheet! I missed that part, unfortunately.

When the VIN > VOUT, the TPS61023 will work in a pass-through operation, so the output voltage will be the VIN - Vdrop (across the DCR of the input and Rds(on) of the PMOS FET).

enter image description here


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