L5981 datasheet(19/37 Pages) STMICROELECTRONICS

Part #	L5981

Description	1A step-down switching regulator

PDF	37 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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19 / 37 page

Application informations

L5981

19/37

minimize the dc error on regulated output voltage; finally to place other poles far away the

zero dB frequency.

In Figure 10 the type III compensation network is shown. This network introduces two zeros

(fZ1, fZ2) and three poles (fP0, fP1, fP2). They expression are:

Equation 16

Equation 17

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.

π C

()

⋅⋅

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

π R

⋅⋅

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

π R

⋅⋅

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

π R

⋅

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

⋅⋅

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

L5981 Datasheet(PDF) 19 Page - STMicroelectronics