L5981 데이터 시트보기 (PDF) - STMicroelectronics

부품명

상세내역

제조사

L5981

1A step-down switching regulator

STMicroelectronics 

Application informations

L5981

Figure 9. The error amplifier, the PWM modulator and the LC output filter.

VCC

VREF

FB

VS

E/A

COMP

PWM

GPW0

OUT

L

ESR

GLC

COUT

The transfer function on the LC filter is given by:

Equation 13

1 + ------------s-------------

GLC(s)

=

-----------------------------2----π----⋅---f--z---E---S----R--------------------

1

+

-------------s---------------

2π ⋅ Q ⋅ fLC

+

⎛

⎝

2----π-----s⋅---f--L---C--⎠⎞

2

where:

Equation 14

fLC

=

-----------------------------------1------------------------------------ ,

2π ⋅

L ⋅ COUT ⋅

1 + --E----S----R----

ROUT

fzESR

=

---------------------1----------------------

2π ⋅ ESR ⋅ COUT

Equation 15

Q = -----R----O----U--L--T--+--⋅---CL-----O⋅---C-U----TO----U⋅---R-T---O-⋅---(U--R--T---O--⋅--U-E---T--S--+--R---E----S-----R-----),

ROUT

=

V-----O----U---T--

IOUT

5.4.1

As seen in Chapter 4.3 two different kind of network can compensate the loop. In the two

following paragraph the guidelines to select the Type II and Type III compensation network

are illustrated.

Type III compensation network

The methodology to stabilize the loop consists of placing two zeros to compensate the effect

of the LC double pole, so increasing phase margin; then to place one pole in the origin to

18/37

Share Link: