Other Parts Discussed in Thread: TPS61230,
Hello -
I am designing a single-cell li-ion charger and uninterruptable power supply using bq25892 and TPS61230. The TPS61230 takes the output from the bq25892 SYS pin and boosts to 5.1V. I do not plan on using a host (bq25892 default-mode ONLY).
Questions:
-I originally had a 787-ohm resistor between the bq25892 ILIM pin and AGND. This was a mistake I made in WEBENCH and subsequently limited my input current to 0.5A. I replaced it with a 56-ohm (all i had on hand) and this theoretically places the input current limit at 6.96A. After powering back up, the system drew 2.1A total instead of the original 0.5A. In either case, I am struggling to get enough output current on the SYS pin to support my TPS61230 output requirement of 5.15V/2.1A (10.815W). I left PSEL pin floating in my current design.
Since I am not using a host, I am struggling to understand the current input selection. Based on my ILIM resistor, and PSEL left floating, I should have a 3.25A current input limit, correct? at 5V input, this should provide 16.25W to the circuit. When the battery charge is complete, that power should nearly all be available at the SYS pin, correct? Or am I missing a parameter?
Basically, I am trying to understand why the circuit does not pull more current when the SYS pin gets loaded.
Thanks in advance,
~asifjahmed
