L7985ATR datasheet(23/42 Pages) STMICROELECTRONICS

Part #	L7985ATR

Description	Voltage feed-forward

PDF	42 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

Logo

23 / 42 page

DocID022446 Rev 7

23/42

L7985

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 non-negligible ESR (> 30 m

), so with

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

the stabilization 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 28

fZ1

 R

4 C4



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

fP0 0

fP1

 R

C4 C5



C4 C5

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



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



L7985ATR Datasheet(PDF) 23 Page - STMicroelectronics