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!
