Diodes AP3502 User Manual
340kHz, 2A Synchronous DC-DC Buck Converter AP3502
Data Sheet
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
SOIC-8
Figure 1. Package Type of AP3502
May. 2012 Rev. 1. 9 BCD Semiconductor Manufacturing Limited
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Data Sheet
340kHz, 2A Synchronous DC-DC Buck Converter AP3502
Pin Configuration
M Package
(SOIC-8)
BS
1
IN
SW
2
3
4
GND
Figure 2. Pin Configuration of AP3502 (Top View)
8
7
6
5
SS
EN
COMP
FB
Pin Description
Pin Number Pin Name Function
Bootstrap pin. A bootstrap capacitor is connected between the BS pin
1
2
3
4
5
6
7
8
BS
and SW pin. The voltage across the bootstrap capacitor drives the
internal high-side power MOSFET
IN
SW
Supply power input pin. A capacitor should be connected between the
IN pin and GND pin to keep the input voltage constant
Power switch output pin. This pin is connected to the inductor and
bootstrap capacitor
GND Ground pin
Feedback pin. This pin is connected to an exte rnal resistor divider to
program the system output voltage. When the FB pin voltage exceeds
FB
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
Compensation pin. This pin is the output of the transconductance
error amplifier and the input to the current comparator. It is used to
COMP
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 required
Control input pin. EN is a digital in put that turns the regulator on or
EN
off. Drive EN high/low to turn on/off the regulator. Pull up with
100kΩ resistor for automatic startup
Soft-start control input pin. SS controls the soft-start period. Connect
SS
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
May. 2012 Rev. 1. 9 BCD Semiconductor Manufacturing Limited
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Data Sheet
340kHz, 2A Synchronous DC-DC Buck Converter AP3502
Functional Block Diagram
2
IN
EN
7
1.5V
SHUTDOWN
COMPARATOR
0.3V
LOCK
COMPARATOR
SCP
INTERNAL
REGULATOR
OSCILLATOR
90k/340k
CLK
VA
VB
SLOP
COMP
CURRENT
SENSE
AMPLIFIER
PWM
COMPARATOR
VA
+
1
M1
Q
S
Q
R
3
M2
BS
SW
2.5 V
SS
VB
6
8
A
EA
5
FB
0.
925V
6
COMP
1.1V
4
GND
Figure 3. Functional Block Diagram of AP3502
Ordering Information
AP3502 -
Circuit Type
Package
M: SOIC-8
Package
Temperature
SOIC-8
Range
-40 to 85°C
Part Number Marking ID Packing Type
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
TR: Tape & Reel
Blank: Tube
May. 2012 Rev. 1. 9 BCD Semiconductor Manufacturing Limited
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Data Sheet
340kHz, 2A Synchronous DC-DC Buck Converter AP3502
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 V
SS Pin Voltage VSS -0.3 to 6 V
Thermal Resistance
Operating Junction Temperature TJ 150 ºC
Storage Temperature T
Lead Temperature (Soldering, 10sec) T
ESD (Human Body Model) VHBM 2000 V
ESD (Machine Model) VMM 200 V
-0.3 to 6 V
COMP
θ
JA
-65 to 150 ºC
STG
260 ºC
LEAD
105 ºC/W
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 periods may affect device reliability.
Recommended Operating Conditions
Parameter Symbol Min Max Unit
Input Voltage VIN 4.5 18 V
Operating Ambient Temperature TA -40 85 ºC
May. 2012 Rev. 1. 9 BCD Semiconductor Manufacturing Limited
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