Dear all,
In need some help finding a part matching all my need.
What I try to achieve: this converter will power a bunch of LEDs controlled by multiple TLC59116 ; it will get its energy from a BQ25895 Li-Ion charger.
What I need:
- Input: 2.7-4.2V in battery-only mode and 3.5-4.2V when plugged-in, from the BQ25895
- Output: from 0 to 2.5A (continuous, not peak, more if possible) @ 4V
- 4V is the absolute minimum, I can go a bit higher (see below)
- Integrated switch
- Not in a BGA package
Following a preliminary search, I found some interesting parts, but none fulfilling all of the above:
- TPS61230: great "zero duty-cycle" mode but not enough current capability ; interestingly, not proposed at all by WeBench
- TPS61230A: Better output current, but "zero duty-cycle" is absent (no idea if it can support Vin>Vout)
- TPS61236P: It's current output is perfect but it requires Vin<Vout-0.6V, meaning an output of 4.8V min
- Other parts were in a BGA package or not were supporting the current requirement
For those wondering why 4V out:
I'm using some TLC59116 LED drivers to, well, drive LEDs. For the constant-current path on each LED to function normally, it needs Vfw+Vol=Vled, with typical blue LED Vfw=3.4V and, @20mA, Vol is between 0.4 and 0.6V, so, in the worst case, I need Vled=4V to have full Vf accross the LED (else the current accross the LEDs would decrease).
Going higher than 4V is just wasting power, dissipated as heat by the chip. For example, using a 5Vout boost converter, we have (5-4)*2.5=2.5W of pure loss, not ideal on battery-powered device.
Considering that, I found that the "zero duty-cycle" of the TPS61230 is excellent, as it allows a simple design, a little overshoot to 4.2V until the battery voltage goes down to 4V, and efficiency.
Best regards,
Guillaume
