Hello,
We use the LM22676 in a power supply with the next parameters:
Vin = 20V to 30V
Vout = 5V
Iout max = 0.8A
Due to capacitors allocation we have to replace the output capacitor.
We have a 150uHy/20% inductor, and we don't want to replace it since we can get the one we already have.
I found few capacitors, and wanted your advice whether they can fit to the design as output capacitors.
1 ) 68uF / 16V / 7mOhm / 20% - when taking in consideration the 20% tolerance of the inductor and the capacitor, the F0 of the pole is 1.3kHz. Since the recommended value of the pole is in the range of 1.5kHz to 15kHz, I wanted to know how critical it is that the pole is lower than that. In what manner the lower pole will be seen?
2) Also, the ESR of this capacitor is very low (7mOhm). I know from other devices that a very low ESR can be problematic in the stability loop. In this device the recommendation is a very low ESR. Can a 7mOhm ESR capacitor be sufficient?
3) Accept output ripple voltage, what should be the criteria for the output capacitor ESR? How high or low and the ESR go?
4) The webench recommended a 33uF capacitor, Can this capacitor stand a 0.8A transient for 2uSec?
Thanks for your help,
Asaf Abraham