LM2575-12 Micrel Semiconductor, LM2575-12 Datasheet - Page 7

• Manufacturer Part Number: LM2575-12
• Description: 52kHz Simple 1A Buck Regulator
• Manufacturer: Micrel Semiconductor

LM2575
Typical Performance Characteristics
Test Circuits and Layout Guidelines
Block Diagrams
August 1999
FEED-
BACK
V IN
UNREGULATED
UNREGULATED
As in any switching regulator, layout is very important. Rapidly switching currents associated with wiring inductance generate voltage transients
which can cause problems. For minimal stray inductance and ground loops, the length of the leads indicated by heavy lines should be kept as
short as possible. Single-point grounding (as indicated) or ground plane construction should be used for best results.
DC INPUT
DC INPUT
1
4
Note: Pin numbers are for TO-220 Package
7V - 40V
7V - 40V
Note: Pin numbers are for the TO-220 package
REFERENCE
BAND-GAP
1.23V
3.1k
1.0k
+
-
FIXED GAIN
ERROR AMP
+
+
OSCILLATOR
V
Voltage
Change
Current
Output
Output
OUT
52 kHz
100 µF
100 µF
C
C
IN
IN
Fixed Regulator
= 5V
+V
+V
+100mV
–100mV
+
IN
IN
-
1
GND
1
GND
COMPARATOR
REGULATOR
INTERNAL
RESET
1.0A
0.5A
LM2575-5.0
0
0
LM2575
3
3
ON/OFF
ON/OFF
SHUTDOWN
THERMAL
Load Transient Response
ON/OFF
5
5
DRIVER
CURRENT
4
2
4
2
LIMIT
FEEDBACK
FEEDBACK
100µS/div.
OUTPUT
OUTPUT
1 AMP
SWITCH
D1
MBR360
D1
MBR360
(Circuit of Figure 1 )
330 µH
330 µH
L1
L1
5
2
3
ON/OFF
OUTPUT
GND
Figure 1.
FEED-
BACK
+
+
7
C
470µF
C
220µF
V IN
OUT
OUT
1
4
REFERENCE
A: Output pin voltage 10V/div
B: Output pin current 1A/div
C: Inductor current 0.5A/div
D: Output ripple voltage 20 mV/div. AC coupled
Horizontal Time Base: 5µs/div
V
5.00V
BAND-GAP
A
B
C
D
OUT
1.23V
V
L
O
A
D
OUT = 5V
10V
R2
R1
.5A
1A
1A
0
0
0
+
-
V
5.00V
FIXED GAIN
ERROR AMP
OSCILLATOR
OUT
L
O
A
D
V
52 kHz
IN = 20V
Adjustable Regulator
+
-
Switching Waveforms
COMPARATOR
REGULATOR
INTERNAL
RESET
C
C
D1 — Schottky, MBR360
L1 — 330µH, 415-0926 (AIE)
R1 — 1k, 0.01%
R2 — 3.065k, 0.01%
5-pin TO-220 socket—2936 (Loranger Mfg. Co.)
4-pin TO-3 socket—8112-AG7 (Augat Inc.)
C
C
D1 — Schottky, MBR360
L1 — 330µH, 415-0926 (AIE)
5-pin TO-220 socket—2936 (Loranger Mfg. Co.)
4-pin TO-3 socket—8112-AG7 (Augat Inc.)
IN
OUT
IN
OUT
— 100µF, 75V Aluminum Electrolytic
— 100µF, 75V Aluminum Electrolytic
— 470µF, 15V Aluminum Electrolytic
— 330µF, 15V Aluminum Electrolytic
SHUTDOWN
THERMAL
ON/OFF
DRIVER
CURRENT
LIMIT
1 AMP
SWITCH
5
2
3
ON/OFF
OUTPUT
GND
M2575
Micrel