AP1522
Step-Up DC/DC 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. 1.0 May. 5, 2005
1/8
Features
- High Efficiency: 84% Typical
- 36V High Output Voltage
- Fast 1MHz Switching Frequency
- Low Profile SOT23-5 Pb-Free Packaging
Applications
- Cellular Phones
- PDAs, Handhelp Computers
- Digital Cameras
- LCD Bias Voltage, Battery Backup
-
General Description
The AP1522 is a step-up DC/DC converter in a
5-Lead low profile SOT23-5 package. The AP1522
switches at 1MHz that allows the use of tiny
external components. A low 1.25V feedback voltage
minimizes power loss in the current setting resistor
for better efficiency.
Pin Assignments
V
IN
SHDN
SW V
SS
FB
Top View
SOT23-5L
Pin Descriptions
Name
Description
SW
Switch Pin. Connect inductor/diode
here. Minimize trace area at this pin
to reduce EMI.
V
SS
GND
pin
FB
Feedback Pin. Reference voltage is
1.25V.
SHDN
Shutdown Pin. Tie to 0.6V or higher
to enable device 0.5Vor less to
disable device.
V
IN
Input Supply Pin. Must be locally
bypassed.
Ordering Information
Package
W: SOT23-5L
AP1522 X X
Packing
Blank : Tube
A : Taping
AP1522
Step-Up DC/DC Converter
Anachip Corp.
www.anachip.com.tw Rev. 1.0 May. 5, 2005
2/8
Block Diagram
1MHz
Oscillator
RAMP
Generator
-
+
-
+
-
+
V
REF
1.25V
V
IN
5
3
FB
R
C
C
C
Comparator
A2
R
S
Q
A1
1
Driver
SW
Q1
2 GND
4
SHDN
Shutdown
Absolute Maximum Ratings
Symbol
Parameter
Rating
Unit
V
IN
V
IN
Pin Voltage
10
V
V
SW
SW Voltage
36
V
V
FB
Feedback Pin Voltage
10
V
V
SHDN
SHDN
Pin
Voltage
10
V
T
J
Maximum Junction Temperature
125
o
C
T
LEAD
Power Dissipation
300
o
C
T
OPR
Operating Temperature Range
-40 to +85
o
C
T
STG
Storage Temperature Range
-40 to +125
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.
AP1522
Step-Up DC/DC Converter
Anachip Corp.
www.anachip.com.tw Rev. 1.0 May. 5, 2005
3/8
Electrical Characteristics
(T
a
=25
°C
, V
IN
= 5V, V
SHDN
= 5V, unless otherwise noted.)
Symbol
Parameter
Conditions
Min.
Typ.
Max.
Unit
V
IN
Minimum Operation Voltage
-
2.5
-
-
V
V
IN
Maximum Operation Voltage
-
-
-
10
V
V
FB
Feedback Pin Voltage
-
1.225
1.25
1.275
V
I
FB
Feedback Pin Bios Current
-
10
45
100
nA
Operation current
-
2
3
mA
Supply
Current
V
SHDN
= 0V
-
0.1
1.0
µA
F
SW
Switching
frequency
0.75
1.0 1.25
MHz
Duty PWM Maximum Duty Cycle
85
90
-
%
I
SW
Switch
Current
Limit
280 320 360 mA
V
SAT
Switch
V
SAT
I
SW
=
250mA
- 350 - mV
Switch
Leakage
Current
V
SW
= 5V
-
0.1
5
µA
V
SHDN
SHDN Pin Voltage High
Enable
0.6
-
-
V
V
SHDN
SHDN Pin Voltage Low
Disable
-
-
0.5
V
I
SHDN
SHDN Pin Bios Current
-
10
-
µA
Typical Application Circuit
Vin
SW
Vss
FB
SHDN
ON OFF
C1
4.7uF
C2
4.7uF
R2
10K
L1
10uH
D1
Vout=10V
R1
70K
Vin=3.3V
Option
V
OUT
=V
FB
(1+ )
R1
R2
1K < R2 < 50K
AP1522
Step-Up DC/DC Converter
Anachip Corp.
www.anachip.com.tw Rev. 1.0 May. 5, 2005
4/8
Typical Application Circuit (Continued)
Step up DC-DC Regulator
V
IN
SW
SHDN
GND
FB
AP1522
C
OUT
4.7uF
20K
L
22uH
D
V
IN
2.5V~3.3V
C
IN
4.7uF
57K
V
OUT
4.8V
4.7pF
1-Cell Li-lon to 3.3V SEPIC Converter
V
IN
SW
SHDN
GND
FB
AP1522
C2
10uF
20K
L1
10uH
D1
V
IN
2.5V to 4.2V
C1
4.7uF
33K
3.3V
50mA
1
5
4
2
3
4.7pF
L2
10uH
C3
1uF
4-Cell to 5V SEPIC Converter
V
IN
SW
SHDN
GND
FB
AP1522
C2
10uF
10K
L1
10uH
D1
V
IN
3V to 6V
C1
4.7uF
30K
5V
40mA
1
5
4
2
3
4.7pF
L2
10uH
C3
1uF
AP1522
Step-Up DC/DC Converter
Anachip Corp.
www.anachip.com.tw Rev. 1.0 May. 5, 2005
5/8
Typical Application Circuit (Continued)
+20V Dual Output Converter with Output Disconnect
V
IN
SW
SHDN
GND
FB
AP1522
C2
10uF
10K
L1
10uH
D1
V
IN
2.5V to 5V
C1
4.7uF
150K
20V
4mA
1
5
4
2
3
4.7pF
C5
1uF
D4
-20V
4mA
D2
D3
C3
1uF
C4
1uF
Applications Information
Inductor Selection
A 10
µ
H inductor is recommended for most AP1522
applications. Although small size and high
efficiency are major concerns, the inductor should
have low core losses at 1MHz and low DCR
(copper wire resistance).
Capacitor Selection
The small size of ceramic capacitors makes them
ideal for AP1522 applications. X5R and X7R types
are recommended because they retain their
capacitance over wider voltage and temperature
ranges than other types such as Y5V or Z5U. A
4.7
µ
F input capacitor and a 4.7
µ
F output capacitor
are sufficient for most AP1522 applications.
Diode Selection
Schottky diodes, with their low forward voltage drop
and fast reverse recovery, are the ideal choices for
AP1522 applications. The forward voltage drop of
a Schottky diode represents the conduction losses
in the diode, while the diode capacitance (C
T
or C
D
)
represents the switching losses. For diode
selection, both forward voltage drop and diode
capacitance need to be considered. Schottky
diodes with higher current ratings usually have
lower forward voltage drop and larger diode
capacitance, which can cause significant switching
losses at the 1MHz switching frequency of the
AP1522. A Schottky diode rated at 100mA to
200mA is sufficient for most AP1522 applications.
Open-Circuit Protection
In the cases of output open circuit, when the R1 are
disconnected from the circuit, the feedback voltage
will be zero. The AP1522 will then switch at a high
duty cycle resulting in a high output voltage, which
may cause the SW pin voltage to exceed its
maximum 36V rating. A zener diode can be used
at the output to limit the voltage on the SW pin
(Figure 1). The zener voltage should be larger
than the maximum forward voltage of the V
OUT
.
The current rating of the zener should be larger
than 0.1mA.
V
IN
SW
SHDN
GND
FB
AP1522
C
OUT
2uF
R3
14K
L
22uH
D
V
IN
C
IN
1uF
R2
1K
R1
200K
4.7pF
Figure 1. With Open-Circuit Protection
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