**Part Number:**TPS7A11

**Other Parts Discussed in Thread:**TPS74801

One or the most typical method to design a suitable PDN is the target impedance method. The datasheet does not contain any graph/chart related to impedance output.

It is indeed possible to make a profile of the output impedance with AC analysis by using any of the Spice model available (even when it is pre-configured for Transient Simulation).

However, my question is: **Is that AC curve something I can trust on**? because it seems that the spice model is not initially intended for AC analysis, just transient.

Analyzing the curve, and modeling the LDO as a simple V-R-L circuit (for PDN simulation in Hyperlynx), the resistance is about R = 3.28 mOhm and inductance L= 1.4uH.

The frequency at which the impedance starts sloping up is 290Hz. Even with 22uF as the bulk capacitor, there is a peak of about 358 mOhm around 28.5KHz

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So, this LDO seems to present a flat response just to 300Hz, then, the bulk capacitor delivers the power for higher frequencies. However, to do so, the bulk must be quite big, in the order of several miliFarads. Trying with other LDO like TPS74801 for example. The performance is quite better, I mean, it provides flat impedance up to 1.12KHz

My question Again. can I trunt in these curves? Should I characterize the LDO in my lab?

Ivan