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MC34167TH

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20
MC34167, MC33167
http://onsemi.com
10
4
2
1
5
3
+
C
F
R
F
R
1
C
O
4700
V
O
5.05 V/5.0 A
R
2
EA
Reference
Thermal
Oscillator
S
R
Q
PWM
UVLO
ILIMIT
V
in
12 V
C
in
330
+
6.8 k
68 k0.1
Q
1
D
1
1N5825
L
190 mH
+
+
+
Test Conditions Results
Line Regulation V
in
= 10 V to 36 V, I
O
= 5.0 A 4.0 mV = ± 0.039%
Load Regulation V
in
= 12 V, I
O
= 0.25 A to 5.0 A 1.0 mV = ± 0.01%
Output Ripple V
in
= 12 V, I
O
= 5.0 A 20 mV
pp
Short Circuit Current
V
in
= 12 V, R
L
= 0.1 W
6.5 A
Efficiency V
in
= 12 V, I
O
= 5.0 A
V
in
= 24 V, I
O
= 5.0 A
78.9%
82.6%
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. 5903B, or 5930B.
The Step−Down Converter application is shown in Figure 19. The output switch transistor Q
1
interrupts the input voltage, generating a
squarewave at the LC
O
filter input. The filter averages the squarewaves, producing a dc output voltage that can be set to any level between
V
in
and V
ref
by controlling the percent conduction time of Q
1
to that of the total oscillator cycle time. If the converter design requires an output
voltage greater than 5.05 V, resistor R
1
must be added to form a divider network at the feedback input.
Figure 19. Step−Down Converter
(Top View)
V
in
V
O
C
O
C
in
L
C
F
RF
R2
R1
D1
+−
+−
+
+
Figure 20. Step−Down Converter Printed Circuit Board and Component Layout
(Bottom View)
3.0″
″
1.9
MC34167 STEP−DOWN
MC34167, MC33167
http://onsemi.com
11
4
2
1
5
3
+
C
F
R
F
R
1
1.5 k
C
O
2200
V
O
28 V/0.9 A
R
2
EA
Reference
Thermal
Oscillator
S
R
Q
PWM
UVLO
ILIMIT
V
in
12 V
C
in
330
+
6.8 k
4.7 k0.47
Q
1
D
1
1N5825
+
*Gate resistor R
G
, zener diode D
3
, and diode D
4
are required only when V
in
is greater than 20 V.
L
190 mH
*R
G
620
D
3
1N967A
D
2
1N5822
Q
2
MTP3055EL
D
4
1N4148
+
+
Test Conditions Results
Line Regulation V
in
= 10 V to 24 V, I
O
= 0.9 A 10 mV = ± 0.017%
Load Regulation V
in
= 12 V, I
O
= 0.1 A to 0.9 A 30 mV = ± 0.053%
Output Ripple V
in
= 12 V, I
O
= 0.9 A 140 mV
pp
Short Circuit Current
V
in
= 12 V, R
L
= 0.1 W
6.0 A
Efficiency V
in
= 12 V, I
O
= 0.9 A
V
in
= 24 V, I
O
= 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 Q
1
and Q
2
. 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 Q
1
is directly in series with V
in
and the load. Second, the
output voltage can be programmed to be less than V
in
. Notice that during the OFF time, the inductor forward biases diodes D
1
and D
2
, transferring
its energy with respect to ground rather than with respect to V
in
. When operating with V
in
greater than 20 V, a gate protection network is required
for the MOSFET. The network consists of components R
G
, D
3
, and D
4
.
Figure 21. Step−Up/Down Converter
(Top View)
V
in
V
O
C
O
C
in
L
C
F
RF
R2
R1
D1
+−
+−
+
+
D3
D2
R
G
Q2
(Bottom View)
Figure 22. Step−Up/Down Converter Printed Circuit Board and Component Layout
3.45
″
″
1.9
MC34167 STEP UP-DOWN
MC34167, MC33167
http://onsemi.com
12
4
2
1
5
3
+
C
F
R
F
R
2
3.3 k
R
1
EA
Reference
Thermal
Oscillator
S
R
Q
PWM
UVLO
ILIMIT
V
in
12 V
C
in
330
+
2.4 k
4.7 k0.47
Q
1
+
C
O
4700
V
O
−12 V/1.7 A
D
1
1N5825
L
190 mH
C
1
0.047
+
+
Test Conditions Results
Line Regulation V
in
= 10 V to 24 V, I
O
= 1.7 A 15 mV = ± 0.61%
Load Regulation V
in
= 12 V, I
O
= 0.1 A to 1.7 A 4.0 mV = ± 0.020%
Output Ripple V
in
= 12 V, I
O
= 1.7 A 78 mV
pp
Short Circuit Current
V
in
= 12 V, R
L
= 0.1 W
5.7 A
Efficiency V
in
= 12 V, I
O
= 1.7 A
V
in
= 24 V, I
O
= 1.7 A
79.5%
86.2%
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. 5903B, or 5930B.
Two potential problems arise when designing the standard voltage−inverting converter with the MC34167. First, the Switch Output emitter is
limited to −1.5 V with respect to the ground pin and second, the Error Amplifier’s noninverting input is internally committed to the reference and
is not pinned out. Both of these problems are resolved by connecting the IC ground pin to the converter’s negative output as shown in Figure 23.
This keeps the emitter of Q
1
positive with respect to the ground pin and has the effect of reversing the Error Amplifier inputs. Note that the voltage
drop across R
1
is equal to 5.05 V when the output is in regulation.
Figure 23. Voltage−Inverting Converter
+
+
+
+
+
+
+
+
+
+
+
+
(Top View)
V
in
V
O
C
O
C
in
L
C
F
RF
R2
R1
D1
+−
+−
+
+
C1
Figure 24. Voltage−Inverting Converter Printed Circuit Board and Component Layout
(Bottom View)
3.0″
″
1.9
MC34167
VOLTAGE-INVERTING
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20

MC34167TH

Mfr. #:
Buy MC34167TH
Manufacturer:
ON Semiconductor
Description:
Switching Voltage Regulators 40V 5A
Lifecycle:
New from this manufacturer.
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