I have a new design with LM27341 converter.
Vin=15-16V
Vout=12V
Cin=10uF+1uF
Cout=10uF+22uF+22uF
L=3.9uH
Prototypes work well, the regulated output was 12V, but the switching signal was not the best. With Vin=16V the signal has some falling peaks during the Ton time:
If i decrease Vin to 15V, one of the peaks disappears:
It is not until 14.2V, when both peaks desappears.
If I increase the inductance to 10uH, the switching was OK.
Now, we have 30 units preserie and the LM27341 is not switching. We have 4.23 in the output. With the oscilloscope before the inductor, we see a 4.23V continuous signal. The same signal at the boost pin. If we increase the inductante to 10uH, the switching is like the first one, with some falling peaks.
We think the matter is with the minimum load current. This situation occurs when the load current is about 30mA. When the load current increases to 200mA the peaks desappear as well.
For high voltage output a minimum load current is required as it is shown in the datasheet.
How can I calc that min current?
Hope you can help me.
Best Regards,
Iker.