MC33167 データシートの表示（PDF） - ON Semiconductor
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MC33167 Datasheet PDF : 20 Pages
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MC34167, MC33167
Vin
12 V
+
Oscillator
PWM
ILIMIT
S
Q
R
UVLO
4
+ Cin
330
Q1
D1
1N5825
2
Thermal
Reference
+
EA
D4
1N4148
+
1
D3
1N967A
R2
6.8 k
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
L
190 µH
*RG
620
Q2
MTP3055EL
D2
1N5822
CO +
2200
VO
28 V/0.9 A
Test
Conditions
Results
Line Regulation
Vin = 10 V to 24 V, IO = 0.9 A
10 mV = ± 0.017%
Load Regulation
Vin = 12 V, IO = 0.1 A to 0.9 A
30 mV = ± 0.053%
Output Ripple
Vin = 12 V, IO = 0.9 A
140 mVpp
Short Circuit Current
Vin = 12 V, RL = 0.1 Ω
6.0 A
Efficiency
Vin = 12 V, IO = 0.9 A
Vin = 24 V, IO = 0.9 A
80.1%
87.8%
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. MC34167: 5903B, or 5930B MTP3055EL: 5925B
Figure 21 shows that the MC34167 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 MC34167, 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
″
(Bottom View)
VO
-+
+ Vin -
+
ÎÎÎÎÎÎÎÎÎÎRFÎÎÎÎÎR1ÎÎÎÎÎCFÎÎÎÎÎ
+
(Top View)
D3
D2 ÎÎÎÎÎRG ÎÎÎ
Figure 22. Step–Up/Down Converter Printed Circuit Board and Component Layout
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