Post Go back to editing

Leave regulated outputs of LTC3554 floating

We're evaluating the LTC3554 for our next design. We need a well-regulated 3.3V, running of a LiPo battery (one cell). The circuit must be able to switch seamlessly between battery supply and charging, as well as powering three high-intensity LEDS (total of ~50mA) during charging, while still being able to determine whether charging the battery or not.

Since the LTC3554 does not boost the battery voltage, we need a separate buck-boost, which we are fine with. However, we don't need the regulated 3.3V and 1.2V that the LTC3554 supplies. We will use Vout to supply a buck-boost (3.3V) and a boost (5V).

Our idea is to do the following.

  • Leave SW1, SW2, FB1 and FB2 floating
  • Tie ~ON, SUSP, PWR_ON1 and PWR_ON2 to ground
  • Tie STBY, and BVIN to VOUT

I'm curious if this will cause any issue during the start-up sequence or (if any adjustments are needed to control the start-up sequence) when "up and running"?

Parents
  • Thank you for your reply.

    I'll update the schematic so that FB1 and FB2 are connected to VOUT.

    The LTC3554 was chosen primarily because of size and power path. Its actually smaller to have the LTC3554 (3x3mm) and the buck-boost we found (1.41x1.41mm), than to have the LTC3566 or LTC3576 (4x4mm). PBSTAT and PGOOD are left floating.

Reply
  • Thank you for your reply.

    I'll update the schematic so that FB1 and FB2 are connected to VOUT.

    The LTC3554 was chosen primarily because of size and power path. Its actually smaller to have the LTC3554 (3x3mm) and the buck-boost we found (1.41x1.41mm), than to have the LTC3566 or LTC3576 (4x4mm). PBSTAT and PGOOD are left floating.

Children
No Data