AP3503
340kHZ 3A SYNCHRONOUS DC-DC BUCK CONVERTER
Description
Pin Assignments
The AP3503 is a 340kHz fixed frequency, current mode, PWM
synchronous buck (step-down) DC-DC converter, capable of driving a
3A load with high efficiency, excellent line and load regulation. The
device integrates N-channel power MOSFET switches with low onresistance. Current mode control provides fast transient response and
cycle-by-cycle current limit.
(Top View)
The AP3503 employs complete protection to ensure system security.
Including output Over Voltage Protection, input Under Voltage
LockOut, programmable soft-start, Over Temperature Protection to
safeguard the circuit.
BS
1
IN
2
SW
3
GND
4
Features
Applications
Input Voltage Range: 4.5V to 18V
LCD TV
Fixed 340kHz Frequency
Set Top Box
High Efficiency: up to 95%
Portable DVD
Output Current: 3A
Digital Photo Frame
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
Document number: DS41526 Rev. 2 - 2
SS
7
EN
6
COMP
5
FB
PSOP-8
This IC is available in PSOP-8 package.
AP3503
EP
8
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AP3503
Typical Applications Circuit
Input Voltage=12V
R4
100k
2
Output Voltage=3.3V
L 10μH
C4
10nF
3
4
C22
C21
22μF/25V 22μF/25V
BS
IN
SW
GND
C5
0.1μF
7
EN
C6
Optional
6
COMP
FB
C11
10μF/25V
8
SS
AP3503
1
C12
10μF/25V
C3
3.3nF
5
R2
D1
Optional
R3
13k
10k
R1
26.1k
Pin Descriptions
Pin Number
Pin Name
1
BS
2
IN
3
SW
Power switch output pin. This pin is connected to the inductor and bootstrap capacitor
4
GND
Ground pin
5
FB
6
COMP
7
EN
8
SS
EP
AP3503
Document number: DS41526 Rev. 2 - 2
Function
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
Supply power input pin. A capacitor should be connected between the IN pin and GND pin to keep the
input voltage constant
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
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 required
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
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
Exposed pad. It should be connected to GND in PCB layout
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AP3503
Functional Block Diagram
2
IN
SHUTDOWN
COMPARATOR
1.5V
VA
INTERNAL
REGULATOR
0.3V
VB
SLOP
COMP
CURRENT
SENSE
AMPLIFIER
VA
+
OSCILLATOR
SCP
1
90 k/340k
BS
M1
CLK
EN
LOCK
COMPARATOR
7
S
Q
R
Q
PWM
COMPARATOR
3
SW
M2
2.5V
VB
1.3V
6 mA
SS
8
FB
Document number: DS41526 Rev. 2 - 2
GND
EA
5
AP3503
4
0.925V
6
COMP
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AP3503
Absolute Maximum Ratings (Note 1)
Symbol
Value
Unit
VIN
IN Pin Voltage
-0.3 to 20
V
VEN
EN Pin Voltage
-0.3 to VIN
V
VSW
SW Pin Voltage
21
V
VBS
BS Pin Voltage
-0.3 to VSW+6
V
VFB
FB Pin Voltage
-0.3 to 6
V
COMP Pin Voltage
-0.3 to 6
V
VSS
SS Pin Voltage
-0.3 to 6
V
θJA
Thermal Resistance
60
ºC/W
TJ
Operating Junction Temperature
+150
ºC
-65 to +150
ºC
VCOMP
Note 1:
Parameter
TSTG
Storage Temperature
TLEAD
Lead Temperature (Soldering, 10sec)
+260
ºC
VHBM
ESD (Human Body Model)
2000
V
VMM
ESD (Machine Model)
200
V
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
Symbol
Parameter
Min
Max
Unit
VIN
Input Voltage
4.5
18
V
TA
Operating Ambient Temperature
-40
+85
ºC
AP3503
Document number: DS41526 Rev. 2 - 2
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AP3503
Electrical Characteristics (TA=+25ºC, VIN=VEN=12V, VOUT=3.3V, unless otherwise specified.)
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
4.5
_
18
V
SUPPLY VOLTAGE (IN PIN)
VIN
Input Voltage
_
IQ
Quiescent Current
VFB=1V,VEN=3V
_
1.2
1.4
mA
Shutdown Supply Current
VEN=0V
_
0.1
10
μA
3.65
4.00
4.25
V
ISHDN
UNDER VOLTAGE LOCKOUT
VUVLO
Input UVLO Threshold
VIN Rising
VHYS
Input UVLO Hysteresis
_
_
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
Feedback Voltage
_
0.907
0.925
0.943
V
Feedback Over Voltage Threshold
_
_
1.1
_
V
Feedback Bias Current
VFB=1V
-0.1
_
0.1
μA
RDSONH
High-side Switch On-resistance (Note 3)
ISW=0.2A/0.7A
_
100
_
mΩ
RDSONL
Low-side Switch On-resistance (Note 3)
ISW=-0.2A/-0.7A
_
100
_
mΩ
High-side Switch Leakage Current
VIN=18V,VEN=VSW=0V
_
0.1
10
μA
ILIMH
High-side Switch Current Limit
_
4.3
5.6
_
A
ILIML
Low-side Switch Current Limit
From drain to Source
_
1.4
_
A
VOLTAGE REFERENCE (FB PIN)
VFB
VFBOV
IFB
MOSFET
CURRENT LIMIT
ILEAKH
SWITCHING REGULATOR
fOSC1
Oscillator Frequency
_
280
340
400
kHz
fOSC2
Short Circuit Oscillator Frequency
_
_
90
_
kHz
DMAX
Max. Duty Cycle
VFB=0.85V
_
90
_
%
DMIN
Min. Duty Cycle
VFB=1V
_
_
0
%
AP3503
Document number: DS41526 Rev. 2 - 2
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AP3503
Electrical Characteristics (Cont. TA=+25ºC, VIN=VEN=12V, VOUT=3.3V, unless otherwise specified.)
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
ERROR AMPLIFIER
AEA
Error Amplifier Voltage Gain (Note 2)
_
_
400
_
V/V
GEA
Error Amplifier Transconductance
_
_
800
_
μA/V
GCS
COMP to Current Sense Transconductance
_
_
5.2
_
A/V
THERMAL SHUTDOWN
TOTSD
Thermal Shutdown (Note 2)
_
_
+160
_
ºC
THYS
Thermal Shutdown Hysteresis (Note 2)
_
_
+20
_
ºC
Soft-start Time (Note 2)
CSS=0.1μF
_
15
_
ms
Soft-start Current
VSS=0V
_
6
_
μA
SOFT START (SS PIN)
tSS
_
Notes:
2. Not tested, guaranteed by design.
3. RDSON=
VSW1 - VSW2
ISW1 - ISW2
AP3503
Document number: DS41526 Rev. 2 - 2
.
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AP3503
Performance Characteristics (TA=+25ºC, VIN=12V, VOUT=3.3V, unless otherwise noted.)
Efficiency vs. Output Current
Quiescent Current vs. Case Temperature
100
1.4
90
1.3
Quiescent Current (mA)
80
Efficiency (%)
70
60
50
o
VOUT=3.3V, TA=25 C, L=10mH
VIN=5V
VIN=12V
40
30
1.2
1.1
1.0
20
10
0.0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
0.9
-50
3.2
-25
0
25
Output Current (A)
75
100
125
150
o
Feedback Voltage vs. Case Temperature
Output Voltage vs. Output Current
1.2
3.6
1.1
3.5
Output Voltage (V)
Feedback Voltage (V)
50
Case Temperature ( C)
1.0
0.9
0.8
3.4
3.3
3.2
3.1
0.7
0.6
-50
3.0
0.0
-25
0
25
50
75
100
125
0.4
0.8
1.2
150
1.6
2.0
2.4
2.8
3.2
Output Current (A)
o
Case Temperature ( C)
High-side Switch On-resistance
Low-side Switch On-resistance
vs. Case Temperature
vs. Case Temperature
160
180
Low-side Switch On-resistance (m)
High-side Switch On-resistance (m)
200
160
140
120
100
80
60
40
-60
-40
-20
0
20
40
60
80
100
120
140
120
100
140
40
-60
-40
-20
0
20
40
60
80
100
120
140
Case Temperature ( C)
Case Temperature ( C)
Document number: DS41526 Rev. 2 - 2
60
o
o
AP3503
80
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AP3503
Performance Characteristics (Cont.
VIN=12V, VOUT=3.3V, unless otherwise noted.)
Output Ripple (IOUT=3A)
Load Transient (IOUT =1.5A to 3A)
VIN_A
VOUT_AC
200mV/div
C
200mV/div
VOUT_AC
20mV/div
IL
2A/div
IOUT
1A/div
VSW
10V/div
Time 4ms/div
Time 200ms/div
Enable Turn on Characteristic
(VIN=12V, VEN=3.3V, VOUT=3.3V, IL=3A)
VEN
2V/div
Enable Turn off Characteristic
(VIN=12V, VEN=3.3V, VOUT=3.3V, IL=3A)
VEN
2V/div
VSS
2V/div
VOUT
2V/div
VSS
2V/div
VOUT
2V/div
IL
2A/div
IL
2A/div
Time 10ms/div
Time 200ms/div
Short Circuit Protection (IOUT=0A)
VOUT
2V/div
Short Circuit Recovery (IOUT=0A)
VOUT
2V/div
IL
2A/div
IL
2A/div
Time 40ms/div
AP3503
Document number: DS41526 Rev. 2 - 2
Time 40ms/div
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AP3503
Ordering Information
AP3503 X X - X
Product Name
Package
Packing
RoHS/Green
MP : PSOP-8
TR : Tape & Reel
Blank : Tube
G1:RoHS Compliant
and Green
Temperature
Range
Package
PSOP-8
Part Number
Marking ID
Packing
AP3503MP-G1
3503MP-G1
Tube
AP3503MPTR-G1
3503MP-G1
Tape & Reel
-40 to +85C
Package Outline Dimensions (All dimensions in mm(inch).)
(1)
Package Type: PSOP-8
3.800(0.150)
4.000(0.157)
2.313(0.091)
3.202(0.126)
3.402(0.134)
2.513(0.099)
1.270(0.050)
TYP
4.700(0.185)
5.100(0.201)
0.330(0.013)
0.510(0.020)
5.800(0.228)
6.200(0.244)
0.050(0.002)
0.150(0.006)
1.350(0.053)
1.550(0.061)
1.350(0.053)
0°
8°
1.750(0.069)
0.400(0.016)
1.270(0.050)
0.170(0.007)
0.250(0.010)
Note: Eject hole, oriented hole and mold mark is optional.
AP3503
Document number: DS41526 Rev. 2 - 2
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AP3503
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INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
(AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION).
Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes
without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the
application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or
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website, harmless against all damages.
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This document is written in English but may be translated into multiple languages for reference. Only the English version of this document is the
final and determinative format released by Diodes Incorporated.
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Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express
written approval of the Chief Executive Officer of Diodes Incorporated. As used herein:
A. Life support devices or systems are devices or systems which:
1. are intended to implant into the body, or
2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the
labeling can be reasonably expected to result in significant injury to the user.
B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the
failure of the life support device or to affect its safety or effectiveness.
Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any
use of Diodes Incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems-related
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representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems.
Copyright © 2018, Diodes Incorporated
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AP3503
Document number: DS41526 Rev. 2 - 2
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