Other Parts Discussed in Thread: TPS61089, TPS61288,
Our design has a one-cell lithium ion capacitor (2.5-3.8V), or two-cell supercapacitors in series (5V in total), as the "last gasp" backup power supply. The system has 12V power supply to old fashioned hard disk, which may require up to 2A peak current during spin-up.
We decide to use two-stage boost to ensure sufficient output at 12V. The first-stage boost converter should squeeze out as much Joules out of capacitors as possible, then boosting to 12V/2A is an easy job for the second stage boost converter (probably the TPS61089).
My question is, among TPS61088 and TPS61288, which one is better to boost from 3V to 6-9V. In datasheets, TPS61088 could generate 27W output at 3.3V Vin, which is very impressive. With ~90% efficiency, the chip squeezes out 30W from the source. For TPS61288, the chip generates 26W output (at 13V) with a better efficiency at 3.6V Vin. Though the output voltage is 1 volt higher, it seems there is no substantial increase in maximum output power compared with TPS61088. This is a surprise since TPS61288 has 15A valley current limit, a whooping 50% increase than that of TPS61088.
All in all we need your advice, which one could generate more output power at around 3V Vin, and how much power could it generate.