MC34167, MC33167 5.0 A, Step−Up/Down/ Inverting ... - RFPhone

MC34167, MC33167
V in
12 V
+
PWM
Oscillator
S
R
Q
ILIMIT
UVLO
4
+
C in
330
Q 1
2 D 1
1N5825
3
Thermal
5
+
C
R 1
Reference
+
EA
R 2
1 6.8 k
C F R F
O
4700
+
L
190 H
V O
5.05 V/5.0 A
0.1
68 k
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 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 A WG
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
3.0″
MC34167 STEP−DOWN
1.9″
V in
+ −
C F
C O
ÉÉÉÉÉ
ÉÉÉÉÉ
RF
R2
C in
D1
L
+
V O
− +
R1
ÉÉÉÉÉ
ÉÉÉÉÉ
+
ÉÉÉÉÉ
ÉÉÉÉÉ
(Bottom View)
(Top View)
Figure 20. Step−Down Converter Printed Circuit Board and Component Layout
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