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"?