AP1520
PWM Control 2A Step-Down Converter
This datasheet contains new product information. Anachip Corp. reserves the rights to modify the product specification without notice. No liability is assumed as a result of the use of
this product. No rights under any patent accompany the sale of the product.
Rev. 1.5 Apr 10, 2006
1/7
Features
- Input voltage: 3.6V to 23V.
- Output voltage: 0.8V to V
CC
.
- Duty ratio: 0% to 100% PWM control
- Oscillation frequency: 300KHz typ.
- Soft-start, Current Limit, Enable function
- Thermal Shutdown function
- Built-in internal SW P-channel MOS
- SOP-8L Pb-Free Package.
Applications
- PC Motherboard
- LCD Monitor
- Graphic Card
- DVD-Video Player
- Telecom Equipment
- ADSL Modem
- Printer and other Peripheral Equipment
- Microprocessor core supply
- Networking power supply
General Description
AP1520 consists of step-down switching regulator
with PWM control. These devices include a reference
voltage source, oscillation circuit, error amplifier,
internal PMOS and etc.
AP1520 provides low-ripple power, high efficiency,
and excellent transient characteristics. The PWM
control circuit is able to vary the duty ratio linearly
from 0 up to 100%. This converter also contains an
error amplifier circuit as well as a soft-start circuit that
prevents overshoot at startup. An enable function,
an over current protect function and a short circuit
protect function are built inside, and when OCP or
SCP happens, the operation frequency will be
reduced from 300KHz to 30KHz. Also, an internal
compensation block is built in to minimum external
component count.
With the addition of an internal P-channel Power MOS,
a coil, capacitors, and a diode connected externally,
these ICs can function as step-down switching
regulators. They serve as ideal power supply units for
portable devices when coupled with the SOP8L
mini-package, providing such outstanding features as
low current consumption. Since this converter can
accommodate an input voltage up to 23V, it is also
suitable for the operation via an AC adapter.
Pin Assignments
1
2
3
4
8
7
6
5
FB
Output
OCSET
AP1520
Output
EN
Vss
Vss
V
CC
Pin Descriptions
Name
Pin
Description
FB 1
Feedback
pin.
EN
2
Power-off pin
H: Normal operation
(Step-down operation)
L: Step-down operation
stopped
(All circuits deactivated)
OCSET 3
Add an external resistor to set
max output current.
V
CC
4 IC power supply pin
Output
56
Switch Pin. Connect external
inductor/diode here. Minimize
trace area at this pin to reduce
EMI.
V
SS
78 GND Pin
AP1520
PWM Control 2A Step-Down Converter
Anachip Corp.
www.anachip.com.tw Rev. 1.5 Apr 10, 2006
2/7
Ordering Information
AP 1520 X X
Package
Packing
S: SOP-8L
Blank : Tube
A : Taping
Block Diagram
Oscillation
Circuit
Reference Voltage
Source with Soft Start
PWM-Switched
Control Circuit
+
-
Vss
V
EN
EN
100uA
OCSET
FB
Vcc
Thermal
Shutdown
Output
Absolute Maximum Ratings
Symbol
Parameter
Rating
Unit
V
CC
V
CC
Pin Voltage
V
SS
- 0.3 to V
SS
+ 25
V
V
FB
Feedback Pin Voltage
V
SS
- 0.3 to V
CC
V
V
EN
EN Pin Voltage
V
SS
- 0.3 to V
IN
+ 0.3
V
V
OUTPUT
Switch
Pin
Voltage
V
SS
- 0.3 to V
IN
+ 0.3
V
P
D
Power Dissipation
Internally limited
mW
T
OPR
Operating Temperature Range
-20 to +125
o
C
T
STG
Storage Temperature Range
-40 to +150
o
C
Caution: The absolute maximum ratings are rated values exceeding which the product could suffer physical damage. These values must
therefore not be exceeded under any conditions.
AP1520
PWM Control 2A Step-Down Converter
Anachip Corp.
www.anachip.com.tw Rev. 1.5 Apr 10, 2006
3/7
Electrical Characteristics
(V
IN
= 12V, T
a
=25
°C
, unless otherwise specified)
Symbol
Parameter
Conditions
Min.
Typ.
Max.
Unit
V
IN
Input
Voltage
--
3.6
-
23 V
V
FB
Feedback
Voltage
I
OUT
=0.1A 0.784
0.8
0.816
V
I
FB
Feedback
Bias
Current I
OUT
=0.1A -
0.1
0.5
ľA
I
SW
Switch
Current
--
2.5
-
-
A
I
SSS
Current Consumption
During Power off
V
EN
=0V -
10
-
ľA
V
OUT
/V
OUT
Line Regulation
V
IN
= 5V~23V
-
1
2
%
V
OUT
/V
OUT
Load Regulation
I
OUT
=0.1 to 2A
-
0.2
0.5
%
f
OSC
Oscillation Frequency
Measure waveform at SW pin
240
300
360
KHz
f
OSC1
Frequency of Current Limit
or Short Circuit Protect
Measure waveform at SW pin
10
-
-
KHz
V
SH
Evaluate oscillation at SW pin
2.0
-
-
V
SL
EN Pin Input Voltage
Evaluate oscillation stop at SW pin
-
-
0.8
V
I
SH
--
-
20
-
ľA
I
SL
EN Pin Input Leakage
Current
--
- -10 - ľA
I
OCSET
OCSET Pin Bias Current
--
75
90
105
ľA
T
SS
Soft-Start
Time
--
0.3
1
2 ms
V
IN
=5V, V
FB
=0V -
110
150
R
DSON
Internal MOSFET Rdson
V
IN
=12V, V
FB
=0V -
70
100
m
EFFI Efficiency
V
IN
= 12V, V
OUT
= 5V
I
OUT
= 2A
- 92 - %
JA
Thermal Resistance
Junction-to-Ambient
-
65
-
o
C/W
Typical Application Circuit
AP1520
+
-
V
SS
EN
C
C
R
A
R
B
D1
FB
Vcc
Output
CVcc
V
OUT
V
IN
R
OCSET
OCSET
C
OUT
C
IN
Optional
C
OCSET
C
EN
R
EN
Option
100K
Note: V
OUT
= V
FB
x (1+R
A
/R
B
)
R
B
=0.7K~5K ohm
L1
22uH
6.8K
1.3K
3K
0.1uF
+
-
C
0.1uF
470uF
680uF
0.1uF
V
IN
=12V, I
MAX
=2A
V
OUT
2.5V 3.3V 5V
L1 Value
22uH 27uH 33uH
AP1520
PWM Control 2A Step-Down Converter
Anachip Corp.
www.anachip.com.tw Rev. 1.5 Apr 10, 2006
4/7
Typical Performance Characteristics
AP1520 Vin v.s. Frequency
(Vout=3.3V; Iout=0.2A)
310
315
320
325
330
335
340
345
350
3.6
4
6
8
10
12
14
16
18
Vin (V)
Fo
sc
(
K
H
z
)
AP1520 Vin v.s. FB
(Vout=3.3V; Iout=0.2A)
0.74
0.75
0.76
0.77
0.78
0.79
0.80
0.81
0.82
0.83
0.84
3.6
4
6
8
10
12
14
16
18
Vin (V)
FB
(
V
)
AP1520 Line Regulation
(Vin=12V; Iout=0.2A)
3.10
3.15
3.20
3.25
3.30
3.35
3.40
3.6
4
6
8
10
12
14
16
18
Vin (V)
V
out (V
)
5.00
5.01
5.02
5.03
5.04
5.05
5.06
5.07
5.08
5.09
5.10
0.0
1.0
2.0
3.0
4.0
Iout (A)
Vout (A)
AP1520 Load Regulation
(Vin=12V)
AP1520 Efficiency
0
10
20
30
40
50
60
70
80
90
100
0.0
0.5
1.0
1.5
2.0
Iout (A)
E
f
f
i
c
i
e
n
cy (
%
)
Vout:5.0V
Vout:3.3V
AP1520
PWM Control 2A Step-Down Converter
Anachip Corp.
www.anachip.com.tw Rev. 1.5 Apr 10, 2006
5/7
Typical Performance Characteristics (Continued)
AP1520 Vout Ripple
(Vin=12V; Vout=3.3V; Iout=0.1A)
AP1520 Vout Ripple
(Vin=12V; Vout=3.3V; Iout=2A)
Test Circuit
A
FB
VCC
VSS
EN
open
open
FB
VCC
VSS
EN
+
-
Osc
i
l
l
a
t
io
n
OUTPUT
OUTPUT
A
FB
VCC
VSS
EN
+
-
+
-
V
OUTPUT
OCSET
OCSET
OCSET
Enable function test
Feedback function test
Operation function test
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