L7980ATR datasheet(21/44 Pages) STMICROELECTRONICS

部件名	L7980ATR

功能描述	2 A step-down switching regulator

PDF	44 Pages

Scroll/Zoom	100%

制造商	STMICROELECTRONICS [STMicroelectronics]

网页	http://www.st.com

标志

21 / 44 page

L7980

Application informations

Doc ID 15181 Rev 4

21/44

Equation 20

Figure 10.

Type III compensation network

In Figure 11 the Bode diagram of the PWM and LC filter transfer function (GPW0 · GLC(f))

and the open loop gain (GLOOP(f) = GPW0 · GLC(f) · GTYPEIII(f)) are drawn.

Figure 11.

Open loop gain: module Bode diagram

The guidelines for positioning the poles and the zeroes and for calculating the component

values can be summarized as follow:

Choose a value for R1, usually between 1 kΩ and 5 kΩ.

Choose a gain (R4/R1) in order to have the required bandwidth (BW), that means:

π R

⋅⋅

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

π R

⋅

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

⋅⋅

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

L7980ATR 数据表(PDF) 21 Page - STMicroelectronics