A7985ATR datasheet(25/44 Pages) STMICROELECTRONICS

Teilenummer	A7985ATR

Bauteilbeschribung	2 A step-down switching regulator for automotive applications

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A7985A

Application information

6.4.2

Type II compensation network

If the equivalent series resistance (ESR) of the output capacitor introduces a zero with

a frequency lower than the desired bandwidth (that is: 2

ESR COUT > 1 / BW), this zero

helps stabilize the loop. Electrolytic capacitors show not-negligible ESR (> 30 m

), so with

this kind of output capacitor the Type II network combined with the zero of the ESR allows

the stabilizing of the loop.

In Figure 13 the Type II network is shown.

Figure 13. Type II compensation network

The singularities of the network are:

Equation 30

fZ1

 R

4 C4



------------------------------

fP0 0

fP1

 R

C4 C5



C4 C5

--------------------



--------------------------------------------



A7985ATR Datenblatt(PDF) 25 Page - STMicroelectronics