Other Parts Discussed in Thread: BQ25616,
Dear TI,
I would like to seek support from you regarding the use of the TPS61027 to power the BQ25616. The BQ25616 works properly when I power it from an external power supply. However, I was not able to make the TPS61027 to work reliably.
If I disconnect the TPS61027 from the BQ25616 (no load, no charging), the TPS61027 output voltage is 4.96, which is quite accurate considering the cable length and multimeter inaccuracy.
However, when I have the TPS61027 connected to BQ25616 (no load, no charging, just idling), the measured output voltage of the TPS becomes about 4.6V.
I do have two output capacitors, one 2.2 uF X5R and the other 47 uF Tantalum. My inductor is 6.2 uH. I wonder if there is something that I can do to make the TPS more stable?
In the second picture, do you think the 2.2 uF (highlighted) and the 47 uF (highlighted) are too far from the chip?
When I replace the 2.2uF capacitor with smaller vaues, I notice that the stabiliy improves. I tried 4.7 uF, 2.2 uF, 1 uF, and 0.5 uF. I notice that 1 uF performs the best. The TPS can take input voltage down to 1.9 V with the output to be approximately 4.9 to 5 V. at 1.8V, the TPS outputs reduced to 4.2V.
Thank you for your time and I look forward to hearing from you.
Khoi
