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TPS54519: Effect of the large inductor current ripple

Part Number: TPS54519
Other Parts Discussed in Thread: TPS62825

Hi there,

I have a basic question on the buck topology while designing TPS54519. The design target is 3.3Vin to 1.0V, 0.776Aload. And to get enough margin and achieve small Vout ripple, I designed very large Cout 94uF, while the calculated min value is 3.35uF. Now I'm considering the inductor value between 1.5u and 3.3uH, and the trade-off between two values are calculated in the table below. For 1.5uH, the inductor current ripple seems too large, as it's usually recommended to be 20 - 40% of the load current. For 3.3uH, the Vovershoot seems too large, though. 

I prefer to use 1.5uH inductor because it has small enough Vout ripple and over/undershoot response for my design. But one thing is the large inductor current.

1. Basically, why is the inductor ripple current recommended to be 20-40% of output current? is it just to prevent the inductor from saturation?

2. Do you expect any problem if I use 1.5uH with this large inductor current, 0.774A? Even though the Cout is large enough to embrace this huge ripple, does this still cause any problem in operation?

L [uH]
(previous)
L [uH]
(current)
1.5 3.3
IL.pp [A]
(previous)
IL.pp [A]
(current)
0.774411 0.352005
Vout [mV]
(previous)
Vout [mV]
(current)
2.025643 0.920747
Vundershoot [mV]
(previous)
Vundershoot [mV]
(current)
2.086735 4.590816
Vovershoot [mV]
(previous)
Vovershoot [mV]
(current)
4.79949 10.55888




Your prompt and kind answer will be really appreciated!