I am designing a board to provide 5 volt power to some custom Mega2560 boards from LiPo batteries. I am looking at a TI DC-DC step up converter (TPS61092) to do the job which has a 1 amp output which is plenty for the board. The trouble is that sometimes these Mega boards will have a GSM daughterboard attached which pulls about 2 amps at 3.8 volts (from an LDO being supplied by the 5v rail) transiently when it transmits.
To cater for the high load I wanted to put a 470-1000uF cap across the output of the TPS61092 to buffer power for the transients. However, the cap will be like shorting the TPS61092 on startup. To minimise the inrush current I could use a resistor between the TPS61092 and the cap however when the GSM transmits I would like it to have unchoked access to the full current from both the cap and the TPS61092.
I could go for a more powerful DC-DC chip however they require more components, more space, more cost and dont' run efficiently at the ~20ma draw of the Mega2560 board when its not transmitting (i.e. most of the time).
Has anyone else had this problem in the past and solved it?