This is not only for TPS564247 but for 12V VIN cases.
I used WEBENCH and got the report.
-- Input --
VIN 12V
VOUT 1V
IOUT 3A
-- Report --
TPS564247DRLR
CIN GRM21BR61E106MA73L x2
Frequency 1.244 MHz
Vin p-p 33.993 mV
CIN capacitor "GRM21BR61E106MA73L x2" is really good choice?
GRM21BR61E106MA73L self resonant frequency is 2.2MHz.
But the plot shift to the right because the capacitance is 83% lost at 12V bias.
fsw is 1.24MHz, so CIN should be chosen so that the impedance is small enough
from 1.24MHz to aprox. 20MHz, especially should be smallest @ 1.24MHz.
I tried simulation and GRM21BR61E106MA73L x2 impedance was 64mOhm at 1.24MHz.
Whereas my choice "GRM32EB31C476ME15 x2", it was 1.44mOhm.
I attach the transient simulation current from VRM as comparison.
This result shows the hot loop extend to the VRM in GRM21BR61E106MA73L x2 case.
I used 3mOhm and 10nH as VRM resistance and inductance, but I don't think it makes big difference.
Any advice on this, please.
