MC34167 ON Semiconductor, MC34167 Datasheet - Page 11

• Manufacturer Part Number: MC34167
• Description: (MC33167 / MC34167) Step-Up/Down/Inverting Switching Regulators
• Manufacturer: ON Semiconductor

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 Q
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 Q
output voltage can be programmed to be less than V
its energy with respect to ground rather than with respect to V
for the MOSFET. The network consists of components R
*Gate resistor R
G
, zener diode D
+
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.
Figure 22. Step−Up/Down Converter Printed Circuit Board and Component Layout
PWM
Line Regulation
Load Regulation
Output Ripple
Short Circuit Current
Efficiency
Oscillator
(Bottom View)
3
3.45
, and diode D
3
″
Test
Thermal
4
are required only when V
Figure 21. Step−Up/Down Converter
in
. Notice that during the OFF time, the inductor forward biases diodes D
V
V
V
V
V
V
in
in
in
in
in
in
MC34167, MC33167
= 10 V to 24 V, I
= 12 V, I
= 12 V, I
= 12 V, R
= 12 V, I
= 24 V, I
G
, D
S
R
http://onsemi.com
1
in
and Q
5
. When operating with V
3
Q
MC34167: 5903B, or 5930B MTP3055EL: 5925B
, and D
+
Conditions
O
O
O
O
in
L
2
= 0.1 A to 0.9 A
= 0.9 A
is greater than 20 V.
= 0.9 A
= 0.9 A
= 0.1 W
. During the OFF time, the energy is transferred, with respect to ground,
11
ILIMIT
4
UVLO
Reference
0.47
.
C
F
O
= 0.9 A
EA
+
V in
+
4.7 k
R
−
in
F
1
Q
+
greater than 20 V, a gate protection network is required
1
is directly in series with V
Î Î Î Î Î
Î Î Î Î Î
Î Î Î Î Î
Î Î Î Î Î
Î Î Î Î Î
Î Î Î Î Î
4
2
1
10 mV = ± 0.017%
30 mV = ± 0.053%
140 mV
6.0 A
80.1%
87.8%
Î Î Î
Î Î Î
1N5825
+
1N4148
12 V
RF
V
−
D
in
D
1
1N967A
1.5 k
V O
4
R
Results
330
C
6.8 k
pp
D
1
R
in
R1
3
+
2
C F
(Top View)
*R
620
G
2200
C
in
+
O
and the load. Second, the
190 mH
1N5822
MTP3055EL
+
D
L
1
2
and D
Q
D2
28 V/0.9 A
2
V
2
O
Î Î
Î Î Î Î
Î
Î Î
Î Î
R G
, transferring
D3