MC33166(2002) 데이터 시트보기 (PDF) - ON Semiconductor

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MC33166
(Rev.:2002)

3.0 A, Step−Up/Down/Inverting Switching Regulators

ON Semiconductor 

MC34166, MC33166

Vin

12 V

+

Oscillator

PWM

Thermal

ILIMIT

S

Q

R

UVLO

Reference

+

EA

4

+ Cin

330

Q1

2

D1

1N5822

D4

1N4148

+

1

D3

1N967A

R2

6.8 k

L

190 µH

*RG

620

Q2

MTP3055EL

D2

1N5822

CO +

1000

VO

28 V/0.6 A

3

5

CF

RF

0.47

4.7 k

*Gate resistor RG, zener diode D3, and diode D4 are required only when Vin is greater than 20 V.

R1

1.5 k

Test

Conditions

Results

Line Regulation

Load Regulation

Output Ripple

Short Circuit Current

Efficiency

Vin = 8.0 V to 24 V, IO = 0.6 A

Vin = 12 V, IO = 0.1 A to 0.6 A

Vin = 12 V, IO = 0.6 A

Vin = 12 V, RL = 0.1 Ω

Vin = 12 V, IO = 0.6 A

23 mV = ± 0.41%

3.0 mV = ± 0.005%

100 mVpp

4.0 A

82.8%

L = Coilcraft M1496–A or General Magnetics Technology GMT–0223, 42 turns of #16 AWG

on Magnetics Inc. 58350–A2 core.

Heatsink = AAVID Engineering Inc. MC34166: 5903B, or 5930B MTP3055EL: 5925B

Figure 21 shows that the MC34166 can be configured as a step–up/down converter with the addition of an external power MOSFET. Energy

is stored in the inductor during the on–time of transistors Q1 and Q2. During the off–time, the energy is transferred, with respect to ground, to

the output filter capacitor and load. This circuit configuration has two significant advantages over the basic step–up converter circuit. The first

advantage is that output short–circuit protection is provided by the MC34166, since Q1 is directly in series with Vin and the load. Second, the

output voltage can be programmed to be less than Vin. Notice that during the off–time, the inductor forward biases diodes D1 and D2, transferring

its energy with respect to ground rather than with respect to Vin. When operating with Vin greater than 20 V, a gate protection network is required

for the MOSFET. The network consists of components RG, D3, and D4.

Figure 21. Step–Up/Down Converter

3.45″

VO

+ Vin -

+

ÎÎÎÎÎÎÎÎÎÎR-FÎÎÎÎÎR+ÎÎÎÎÎ1 CFÎÎÎÎÎ

+

D3

D2 ÎÎÎÎÎRG ÎÎÎÎÎ

(Bottom View)

(Top View)

Figure 22. Step–Up/Down Converter Printed Circuit Board and Component Layout

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