Other Parts Discussed in Thread: LMR33620
Hello Team, customer has following question:
we have calculated the minimum output ripple voltage for our buck DCDC design with the LMR33620A-Q1 (LMR33620AQ5RNXRQ1).
Based on our worst case calculation we get an output voltage ripple between 0.19 mV to 4.0 mV.
I have two question:
- a) Is our enclosed calculation correct?
- b) Is there any minimum output voltage ripple required by the LMR33620A, which we shall not fall below?
For the calculation we used the equitation from the datasheet:
With the following parameters:
∆IL: 0.36 (min) / 0.73 (typ) / 1.69 (max) [Ap-p] inductor ripple current
fsw: 340 (min) / 400 (typ) / 460 (max) [khz]
Cout: 169 (min) / 340 (typ) / 507 (max) [µF] (2x 4.7µF / X7R / 16V parallel to 1x 330 µF low ESR electrolytic cap)
ESR: expected as 0, since several ceramic caps used in parallel to one electrolytic cap
So that we get:
Vr: 0.19 (min) / 0.67 (typ) / 4 (max) [mV]
Many Thanks
Josef
