I'm trying to use the TPS62290 in a 1S Lipo configuration to provide 2.0v to a microcontroller.
I've ran into a problem however and I don't know if it's my design or the part.
I copied the reference design completely, using the specified parts, it's as simple as that. Input capacitor 10uf x7r, device, output to a 2.2uf coilcraft 3015 inductor, 430k/180k voltage divider with a 22pf across the top resistor, and a 10uF output cap. EN it tied high, and MODE is tied to ground.
if you look at the data sheet the schematic is exactly the same except for the VD to correct for 2.0v.
Output voltage is fine, and current capability is fine... it's an issue with low current that has me perplexed.
With a 2ma load, I'm seeing 7ma draw from the battery, where at at 10ma load, I see approx 10ma draw and at full load - 50ma, I see 35ma of current draw.
It's the low end that I'm trying to figure out, is this just an issue with this part, it being not very efficient when low current is being required?
I've verified the by removing any load and powering the input, indeed I see no current from the battery, now add a 4.7k resistor as the load and I see 5Ma of current.
I built a second board just to rule out any component issues and it behaves exactly the same. it's acting like it's not in PFM, but in PWM mode when the current requirement is low.... OR I'm just in it's extremely under efficient current providing area?
Any help appreciated.
Full circuit is here - https://dl.dropboxusercontent.com/u/6730484/Boost-Solar%20Voltage.pdf... I've removed the last component from the PV controller side to rule out any issues there. That made no difference.
All the above is with a single source, the 3.0-4.2v lipo battery, usb and or PV is NOT connected.
Thanks in advance,
Alan
