Hello,
I have a layout that uses the TPS55340 to boost from a 7.8V Li-ion battery to a 24V output driving 0.7A. I'm having issues:
When I enable the TPS55340, it activates for a very brief period (<10ms) and then immediately disables itself. Just before it turns off I measure about ~0.5A current. It occurs to me that possible there is a current spike happening (that I am not seeing), which may be engaging the over current protection on the switch. Does this seem possible/likely? If so, what is the best way to verify that this is indeed what is occurring? Note: If I artificially limit the current into the converter, it activates like it should and drives the output.
Otherwise, what else could cause this behaviour?
Supplementary info:
Vin=5-7.8V, Vout = 24V, Iout = 0.7A, f=600kHz
Ci=10uF, Co=9.8uF, Css=0.047uF, Ccomp=0.1uF, Chf= 680pF, Rsh=187k, Rsl=10k, Rfreq=78.7k
L = 10uH => I_peak = 4.3A (my inductor is rated for more than this, and my measured input current is less than this).
- For the condition where the output turns on like it should, I measure the switching frequency at SW to be ~579kHz.
- The inductor produces a high pitched whine when it is on.
- My scope measures the duty cycle @ SW to be only ~11-15%. This seems very low based on my design.
