We currently make an instrument that uses an LTC3525-3.3V (Linear Technologies) step-up DC/DC converter to generate 3.3V from 2 x AA cells. However, the LTC3525 has become expensive to source in low quantities ($6 for < 500 from digikey and element14) so we are looking for a part to replace it.
The instrument is a data logger designed to run for a very long time. Normally it consumes < 100uA, but there are periodic writes to an SD card which consume up to 100mA for a very short period of time.
The features of the LCT3525 which make it attractive are:
- 100mA out (max) at 1.25V
- 7uA quiescent current
- 92% max efficiency @ 2.4V (85% efficiency @ 0.1mA at 2.4V)
- Vin > Vout operation up to 4.5V
- Min Vin once started of 0.5V
Looking at the TI catalog, it seems the TPS61221 or TPS61097A-33 would be good replacements.
- Are there any other parts I should be looking at?
- Apart from minimum voltage and quiescent current, is there any difference between these two TI parts?
- The TPS61097A has MSP430 in its list of applications, any reason why apart from low Iq?
- What happens during Vin > Vout?
