Data Sheet
340kHz, 2A Synchronous DC-DC Buck Converter AP3502
May. 2012 Rev. 1. 9 BCD Semiconductor Manufacturing Limited
1
General Description
The AP3502 is a 340kHz fixed frequency, current
mode, PWM synchronous buck (step-down) DC-DC
converter, capable of driving a 2A load with high
efficiency, excellent line and load regulation. The
device integrates N-channel power MOSFET
switches with low on-resistance. Current mode
control provides fast transient response and
cycle-by-cycle current limit.
The AP3502 employs complete protection to ensure
system security, including output Over Voltage
Protection, input Under Voltage LockOut,
programmable soft-start, and Over Temperature
Protection.
This IC is available in SOIC-8 package.
Features
• Input Voltage Range: 4.5V to 18V
• Fixed 340kHz Frequency
• High Efficiency: up to 95%
• Output Current: 2A
• Current Mode Control
• Built-in Over Current Protection
• Built-in Thermal Shutdown Function
• Built-in UVLO Function
• Built-in Over Voltage Protection
• Programmable Soft-start
Applications
• LCD TV
• Set Top Box
• Portable DVD
• Digital Photo Frame
Figure 1. Package Type of AP3502
SOIC-8
Data Sheet
340kHz, 2A Synchronous DC-DC Buck Converter AP3502
May. 2012 Rev. 1. 9 BCD Semiconductor Manufacturing Limited
2
Pin Configuration
M Package
(SOIC-8)
Figure 2. Pin Configuration of AP3502 (Top View)
Pin Description
Pin Number Pin Name Function
1 BS Bootstrap pin. A bootstrap capacitor is connected between the BS pin
and SW pin. The voltage across the bootstrap capacitor drives the
internal high-side power MOSFET
2 IN Supply power input pin. A capacitor should be connected between the
IN pin and GND pin to keep the input voltage constant
3 SW Power switch output pin. This pin is connected to the inductor and
bootstrap capacitor
4 GND Ground pin
5 FB
Feedback pin. This pin is connected to an external resistor divider to
program the system output voltage. When the FB pin voltage exceeds
1.1V, the over voltage protection is triggered. When the FB pin
voltage is below 0.3V, the oscillator frequency is lowered to realize
short circuit protection
6 COMP
Compensation pin. This pin is the output of the transconductance
error amplifier and the input to the current comparator. It is used to
compensate the control loop. Connect a series RC network from this
pin to GND. In some cases, an additional capacitor from this pin to
GND pin is requi red
7 EN Control input pin. EN is a digital input that turns the regulator on or
off. Drive EN high/low to turn on/off the regulator. Pull up with
100kΩ resistor for automatic startup
8 SS
Soft-start control input pin. SS controls the soft-start period. Connect
a capacitor from SS to GND to set the soft-start period. A 0.1µF
capacitor sets the soft-start period to 15ms. To disable the soft-start
feature, leave SS unconnected
1
2
3
4
8
7
6
5
BS
IN
SW
GND FB
COMP
EN
SS
Data Sheet
340kHz, 2A Synchronous DC-DC Buck Converter AP3502
May. 2012 Rev. 1. 9 BCD Semiconductor Manufacturing Limited
3
TR: Tape & Reel
Blank: Tube
Functional Block Diagram
S
R
Q
Q
INTERNAL
REGULATOR
OSCILLATOR
2
7
5
4
3
1
VA
BS
SW
GND
EA
6
COMP
FB
EN
IN
COMPARATOR
8
SS
CURRENT
SENSE
AMPLIFIER
CLK
SLOP
COMP
PWM
COMPARATOR
1.1V
+
SCP
VA
VB
VB
6A
90k/340k
0. 925V
2.5V
M1
M2
0.3V
COMPARATOR
1.5V SHUTDOWN
LOCK
Figure 3. Functional Block Diagram of AP3502
Ordering Information
AP3502 -
Circuit Type
Package Temperature
Range Part Number Marking ID Packing Type
SOIC-8 -40 to 85°C AP3502M-G1 3502M-G1 Tube
AP3502MTR-G1 3502M-G1 Tape & Reel
BCD Semiconductor's Pb-free products, as designated with "G1" suffix in the part number, are RoHS compliant
and green.
G1: Green
Package
M: SOIC-8
Data Sheet
340kHz, 2A Synchronous DC-DC Buck Converter AP3502
May. 2012 Rev. 1. 9 BCD Semiconductor Manufacturing Limited
4
Absolute Maximum Ratings (Note 1)
Parameter Symbol Value Unit
IN Pin Voltage VIN -0.3 to 20 V
EN Pin Voltage VEN -0.3 to VIN V
SW Pin Voltage VSW 21 V
BS Pin Voltage VBS -0.3 to VSW+6 V
FB Pin Voltage VFB -0.3 to 6 V
COMP Pin Voltage VCOMP -0.3 to 6 V
SS Pin Voltage VSS -0.3 to 6 V
Thermal Resistance θJA 105 ºC/W
Operating Junction Temperature TJ 150 ºC
Storage Temperature TSTG -65 to 150 ºC
Lead Temperature (Soldering, 10sec) TLEAD 260 ºC
ESD (Human Body Model) VHBM 2000 V
ESD (Machine Model) VMM 200 V
Note 1: Stresses greater than those listed under “Absolute Maximum Ratings” may cause permanent damage to
the device. These are stress ratings only, and functional operation of the device at these or any other conditions
beyond those indicated under “Recommended Operating Conditions” is not implied. Exposure to “Absolute
Maximum Ratings” for extended p eriods may affect device reliability.
Recommended Operating Conditions
Parameter Symbol Min Max Unit
Input Voltage VIN 4.5 18 V
Operating Ambient T emperature TA -40 85 ºC
Data Sheet
340kHz, 2A Synchronous DC-DC Buck Converter AP3502
May. 2012 Rev. 1. 9 BCD Semiconductor Manufacturing Limited
5
Electrical Characteristics
TA=25ºC, VIN=VEN=12V, VOUT=3.3V, un less otherwise specified.
Parameter Symbol Conditions Min Typ Max Unit
SUPPLY VOLTAGE (IN PIN)
Input Voltage VIN 4.5 18 V
Quiescent Current IQ V
FB=1V,VEN=3V 1.2 1.4 mA
Shutdown Supply Current ISHDN V
EN=0V 0.1 10
µA
UNDER V OLTAGE LOCKOUT
Input UVLO Threshold VUVLO VIN Rising 3.65 4.00 4.25 V
Input UVLO Hysteresis VHYS 200 mV
ENABLE (EN PIN)
EN Shutdown Threshold Voltage 1.1 1.5 2 V
EN Shutdown Threshold Voltage Hysteresis
(Note 2) 350 mV
EN Lockout Threshold Voltage 2.2 2.5 2.7 V
EN Lockout Hysteresis 210 mV
VOLTAGE REFERENCE (FB PIN)
Feedback Voltage VFB 0.907 0.925 0.943 V
Feedback Over Voltage Threshold VFBOV 1.1 V
Feedback Bias Current IFB V
FB=1V -0.1 0.1
µA
MOSFET
High-side Switch On-resistance(Note 3) RDSONH ISW=0.2A/0.7A
100 mΩ
Low-side Switch On-resistance(Note 3) RDSONL ISW=-0.2A/-0.7A
100 mΩ
CURRENT LIMIT
High-side Switch Leakage Current ILEAKH VIN=18V,VEN=VSW=0V 0.1 10
µA
High-side Switch Current Limit ILIMH 2.7 3.5 A
Low-side Switch Current Limit ILIML From Drain to Source 1.4 A
SWITCHING REGULATOR
Oscillator Frequency fOSC1 280 340 400 kHz
Short Circuit Oscillator Frequency fOSC2 90 kHz
Max. Duty Cycle DMAX V
FB=0.85V 90 %
Min. Duty Cycle DMIN V
FB=1V 0 %
ERROR AMPLIFIER
Error Amplifier Voltage Gain (Note 2) AEA 400 V/V
Error Amplifier Transconductance GEA 800
µ
A/V
COMP to Current Sense Transconductance GCS 3.5 A/V
THERMAL SHUTDOWN
Thermal Shutdown (Note 2) TOTSD 160 ºC
Thermal Shutdown Hysteresis (Note 2) THYS 30 ºC
SOFT START (SS PIN)
Soft-start Time (Note 2) tSS CSS=0.1µF 15 ms
Soft-start Current VSS=0V 6
µA
Note 2: Not test ed, guaranteed by desig n.
Note 3: RDSON=
SW2SW1
SW2SW1 I-I V-V .
Data Sheet
340kHz, 2A Synchronous DC-DC Buck Converter AP3502
May. 2012 Rev. 1. 9 BCD Semiconductor Manufacturing Limited
6
Typical Performance Characteristics
TA=25ºC, VIN=12V, VOUT=3.3V, unless otherwise not ed.
Figure 4. Efficiency vs. Output Current Figure 5. Quiescent Current vs. Case Temperature
Figure 6. Feedback Voltage vs. Case Temperature Figure 7. Output Voltage vs. Output Current
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2
30
40
50
60
70
80
90
100
Efficiency (%)
Output Current (A)
VOUT=3.3V, L=10µH, TA=25oC
VIN=5V
VIN=12V
-50 -25 0 25 50 75 100 125 150
0.9
1.0
1.1
1.2
1.3
1.4
Quiescent Current (mA)
Case Te mp er ature (oC)
-50 -25 0 25 50 75 100 125 150
0.6
0.7
0.8
0.9
1.0
1.1
1.2
Feedback Voltage (V)
Case Temper at ur e ( oC)
0.00.20.40.60.81.01.21.41.61.82.02.2
3.0
3.1
3.2
3.3
3.4
3.5
3.6
Output Voltage (V)
Output Current (A)
Data Sheet
340kHz, 2A Synchronous DC-DC Buck Converter AP3502
May. 2012 Rev. 1. 9 BCD Semiconductor Manufacturing Limited
7
Typical Performance Characteristics (Continued)
TA=25ºC, VIN=12V, VOUT=3.3V, unless otherwise not ed.
Figure 8. High-side Switch On-resistance Figure 9. Low-side Switch On-resistance
vs. Case Temperature vs. Case Temperature
Figure 10. Output Ripple (IOUT=2A) Figure 11. Load Transient (IOUT =1A to 2A)
-60 -40 -20 0 20 40 60 80 100 120 140
40
60
80
100
120
140
160
180
200
High-side Switch On-resistance (mΩ)
Case Temper at ur e ( oC)
-60 -40 -20 0 20 40 60 80 100 120 140
40
60
80
100
120
140
160
Low-side Switch O n- resistance (mΩ)
Case Temperature (oC)
VIN_AC
200mV/div
VOUT_AC
20mV/div
IL
1A/div
VSW
10V/div
Time 2µs/div
VOUT_AC
100mV/div
IOUT
1A/div
Time 200µs/div
Data Sheet
340kHz, 2A Synchronous DC-DC Buck Converter AP3502
May. 2012 Rev. 1. 9 BCD Semiconductor Manufacturing Limited
8
Typical Performance Characteristics (Continued)
TA=25ºC, VIN=12V, VOUT=3.3V, unless otherwise not ed.
Figure 12. Enable Turn on Characteristic Figure 13. Enable Turn off Characteristic
(VIN=12V, VEN=3.3V, VOUT=3.3V, IL=2A) (V
IN=12V, VEN=3.3V, VOUT=3.3V, IL=2A)
Figure 14. Short Circuit Protection (IOUT=0A) Figure 15. Short Circuit Recovery (I
OUT=0A)
VOUT
2V/div
IL
2A/div
Time 40µs/div
IL
2A/div
Time 40µs/div
VEN
2V/div
VSS
2V/div
VOUT
2V/div
IL
1A/div
Time 10ms/div Time 200µs/div
VEN
2V/div
VSS
2V/div
VOUT
2V/div
IL
1A/div
VOUT
2V/div
Data Sheet
340kHz, 2A Synchronous DC-DC Buck Converter AP3502
May. 2012 Rev. 1. 9 BCD Semiconductor Manufacturing Limited
9
Typical Application
C3
4.7nF
C11
10µF/25V
C22
22µF/25V D1
Optional
L 10µH
R4
100k
R2 10k
R1
26.1k
R3
13k
C6
Optional
C4
10nF
C5
0.1µF
3
5
1
6
7
8
2
4
AP3502
BS
IN
SW
GND FB
COMP
EN
SS
C21
22µF/25V
Input Voltage=12V
Output Voltage=3.3V
Figure 16. Typical Application of AP3502
Data Sheet
340kHz, 2A Synchronous DC-DC Buck Converter AP3502
May. 2012 Rev. 1. 9 BCD Semiconductor Manufacturing Limited
10
Mechanical Dimensions
SOIC-8 Unit: mm(inch)
0°
8°
1°
5°
R0.150(0.006)
R0.150(0.006)
1.000(0.039)
0.330(0.013)
0.510(0.020)
1.350(0.053)
1.750(0.069)
0.100(0.004)
0.300(0.012)
0.900(0.035)
0.800(0.031)
0.200(0.008)
3.800(0.150)
4.000(0.157)
7°
7°
20:1
D
1.270(0.050)
TYP
0.190(0.007)
0.250(0.010)
8°
D
5.800(0.228)
6.200(0.244)
0.675(0.027)
0.725(0.029)
0.320(0.013)
8°
0.450(0.017)
0.800(0.031)
4.700(0.185)
5.100(0.201)
Note: Eject hole, oriented hole and mold mark is optional.
IMPORTANT NOTICE
BCD Semiconductor Manufacturing Limited reserves the right to make changes without further notice to any products or specifi-
cations herein. BCD Semiconductor Manufacturing Limited does not assume any responsibility fo r use of any its products for any
particular purpose, nor does BCD Semiconductor Man ufacturing Limited assume any liability arising out of the application or use
of any its products or circuits. BCD Semiconductor Manufacturing Limited does not convey any license under its patent rights or
other rights nor the rights of others.
- Wafer Fab
Shanghai SIM-BCD Semiconductor Manufacturing Limited
800, Yi Shan Road, Shanghai 200233, China
Tel: +86-21-6485 1491, Fax: +86-21-5450 0008
BCD Semiconductor Manufacturing Limited
MAIN SITE
REGIONAL SALES OFFICE
Shenzhen Office
Shanghai SIM-BCD Semiconductor Manufacturing Co., Ltd. Shenzhen Office
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Tel: +86-755-8826 7951
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BCD Semiconductor Manufacturing Limited
http://www.bcdsemi.com
BCD Semiconductor Manufacturing Limited
IMPORTANT NOTICE
BCD Semiconductor Manufacturing Limited reserves the right to make changes without further notice to any products or specifi-
cations herein. BCD Semiconductor Manufacturing Limited does not assume any responsibility for use of any its products for any
particular purpose, nor does BCD Semiconductor Manufacturing Limited assume any liability arising out of the application or use
of any its products or circuits. BCD Semiconductor Manufacturing Limited does not convey any license under its patent rights or
other rights nor the rights of others.
- Wafer Fab
Shanghai SIM-BCD Semiconductor Manufacturing Co., Ltd.
800 Yi Shan Road, Shanghai 200233, China
Tel: +86-21-6485 1491, Fax: +86-21-5450 0008
MAIN SITE
REGIONAL SALES OFFICE
Shenzhen Office
Shanghai SIM-BCD Semiconductor Manufacturing Co., Ltd., Shenzhen Office
Unit A Room 1203, Skyworth Bldg., Gaoxin Ave.1.S., Nanshan District, Shenzhen,
China
Tel: +86-755-8826 7951
Fax: +86-755-8826 7865
Taiwan Office
BCD Semiconductor (Taiwan) Company Limited
4F, 298-1, Rui Guang Road, Nei-Hu District, Taipei,
Taiwan
Tel: +886-2-2656 2808
Fax: +886-2-2656 2806
USA Office
BCD Semiconductor Corp.
30920 Huntwood Ave. Hayward,
CA 94544, USA
Tel : +1-510-324-2988
Fax: +1-510-324-2788
- Headquarters
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No. 1600, Zi Xing Road, Shanghai ZiZhu Science-based Industrial Park, 200241, China
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