SC4612 데이터 시트보기 (PDF) - Semtech Corporation

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SC4612

Wide Input Range High Performance Synchronous Buck Switching Controller

Semtech Corporation 

SC4612

POWER MANAGEMENT

Application Information (Cont.)

The design guidelines are as following:

1. Set the loop gain crossover frequency wC for given

switching frequency.

2. Place an integrator at the origin to increase DC and low

frequency gains.

3. Select wZ1 and wZ2 such that they are placed near wO to

dampen peaking; the loop gain should cross 0dB at a rate

of -20dB/dec.

4. Cancel wESR with compensation pole wP1 (wP1 = wESR ).

5. Place a high frequency compensation pole wP2 at half

the switching frequency to get the maximum attenuation

of the switching ripple and the high frequency noise with

adequate phase lag at wC.

T

ω Z1

ωo

Loop gain T(s)

ωZ2

Gd

ωc

0dB

ω p1

ω p2

ω ESR

Figure 2. Simplified asymptotic diagram of buck power

stage and its compensated loop gain.

Switching Frequency, FSW vs. COSC.

1200

1100

1000

900

800

700

600

500

400

300

200

100

0

0

100 200 300 400 500 600 700 800 900 1000 1100 1200

Frequency, (kHz)

Table 1

 2007 Semtech Corp.

13

www.semtech.com

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