AP3428/A
1.5MHZ, 1A STEP-DOWN DC-DC BUCK CONVERTER
Description
Pin Assignments
NEW PRODUCT
The AP3428/A is a 1A step-down DC-DC converter. At heavy load,
the constant-frequency PWM control performs excellent stability and
transient response. No external compensation components are
required.
(Top View)
The AP3428/A supports a range of input voltages from 2.5V to 5.5V,
allowing the use of a single Li+/Li-polymer cell, multiple Alkaline/NiMH
cell, and other standard power sources. The output voltage is
adjustable from 0.6V to the input voltage. The AP3428/A employs
internal power switch and synchronous rectifier to minimize external
part count and realize high efficiency. During shutdown, the input is
disconnected from the output and the shutdown current is less than
1μA. Other key features include over-temperature and short circuit
protection, and under-voltage lockout to prevent deep battery
discharge.
EN
1
GND
2
LX
3
5
FB
4
VIN
TSOT25 for AP3428
(Top View)
The AP3428/A delivers 1A maximum output current while consuming
only 40μA of no-load quiescent current. Ultra-low RDS(ON) integrated
MOSFETs and 100% duty cycle operation make the AP3428/A an
ideal choice for high output voltage, high current applications which
require a low dropout threshold. Pulse skip mode allows to maintain
high efficiency at light-load conditions.
VIN
1
GND
2
EN
3
5
LX
4
FB
TSOT25 for AP3428A
The AP3428/A is available in TSOT25, U-DFN2020-6 (Type J)
packages.
(Top View)
Features
P in 1 Mark
Output Current: Up to 1A
Output Voltage: 0.6V to VIN
Input Voltage: 2.5V to 5.5V
0.6V Reference Voltage With ±2% Precision
40µA (Typ) No Load Quiescent Current
Shutdown Current: <1µA
100% Duty Cycle Operation
1.5MHz Switching Frequency
Internal Soft Start
No External Compensation Required
Current Limit Protection
Applications
Thermal Shutdown
Post DC-DC Voltage Regulation
TSOT25, U-DFN2020-6 (Type J) Packages
Set Top Boxes
Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)
Notebook Computer
Halogen and Antimony Free. “Green” Device (Note 3)
PAD
Notes:
NC
1
6
FB
EN
2
5
GND
VIN
3
4
LX
U-DFN2020-6 (Type J)
1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.
2. See http://www.diodes.com/quality/lead_free.html for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green"
and Lead-free.
3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and
<1000ppm antimony compounds.
AP3428/A
Document number: DS37417 Rev. 2 - 2
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AP3428/A
Typical Applications Circuit
VIN=2.5V to 5.5V
VIN
NEW PRODUCT
GND
ON
OFF
AP3428/A
CIN
10mF
EN
L1 2.2mH
VOUT=1.8V
LX
C1
22pF
R1
300k
COUT
10mF
FB
R2
150k
Pin Descriptions
Pin Number
TSOT25 for
AP3428
TSOT25 for
AP3428A
U-DFN2020-6
(Type J)
Pin Name
Function
1
3
2
EN
Enable control input. Force this pin voltage above 1.5V enables the
chip, and below 0.4V shuts down the device.
2
2
5
GND
3
5
4
LX
The drains of the internal main and synchronous power MOSFET.
4
1
3
VIN
Bias supply. Chip main power supply pin
5
4
6
FB
Feedback voltage to internal error amplifier, the threshold voltage
is 0.6V.
–
–
1
NC
NC
AP3428/A
Document number: DS37417 Rev. 2 - 2
Ground pin
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AP3428/A
Functional Block Diagram
VIN
EN
1(3){2}
4(1){3}
NEW PRODUCT
Slope
Compensation
OCP
Comparator
Oscillator
Current
Sensing
Shutdown
Comparator
Bias
Generator
Control
Logic
Buffer &
Dead Time
Control
Logic
3(5){4}
LX
PWM
Comparator
Soft
Start
FB
UVLO
5(4){6}
Reverse Inductor
Current Comparator
Error
Amplifier
2(2){5}
GND
VIN OVP Comparator
Bandgap
Reference
A: TSOT25 for AP3428
(B): TSOT25 for AP3428A
{C}: U-DFN2020-6
AP3428/A
Document number: DS37417 Rev. 2 - 2
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AP3428/A
Absolute Maximum Ratings (Note 4)
NEW PRODUCT
Symbol
Rating
Unit
-0.3 to 6
V
VIN
Input Voltage
VEN
EN Pin Voltage
-0.3 to VIN+0.3
V
VLX
LX Pin Voltage
-0.3 to VIN+0.3
V
VFB
Feedback Pin Voltage
-0.3 to VIN+0.3
V
PD
Power Dissipation (on PCB, TA = +25°C)
θJA
Thermal Resistance (Junction to Ambient)
θJC
Thermal Resistance (Junction to Case, Simulation)
TJ
Note 4:
Parameter
TSOT25
0.4
U-DFN2020-6
(Type J)
1.89
TSOT25
220
U-DFN2020-6
(Type J)
53
TSOT25
130
U-DFN2020-6
(Type J)
25
Operating Junction Temperature
W
°C/W
ºC/W
+155
°C
TSTG
Storage Temperature
-55 to +150
°C
VMM
ESD (Machine Model)
200
V
VHBM
ESD (Human Body Model)
2000
V
VCDM
ESD (Charge Device Mode)
1000
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
Supply Voltage
2.5
5.5
V
TJ
Junction Temperature Range
-40
+125
°C
TA
Operating Ambient Temperature
-40
+85
°C
AP3428/A
Document number: DS37417 Rev. 2 - 2
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AP3428/A
Electrical Characteristics (@TA = +25ºC, VIN = 5.0V, VOUT = 2.5V, COUT = 10µF, L = 2.2µH, unless otherwise specified.)
Symbol
Condition
Min
Typ
Max
Unit
Input Voltage Range
–
2.5
–
5.5
V
Output Voltage Range
–
0.6
–
VIN
V
IQ
Quiescent Current
VFB = 0.65V
–
40
–
µA
ISD
Shutdown Current
VEN = 0V
–
0.1
1
µA
VFB
Regulated Feedback Voltage
–
0.588
0.6
0.612
V
IFB
FB Leakage Current
VFB = 1V
–
–
0.2
µA
ILIM
Peak Inductor Current
–
1.3
–
–
A
fOSC
Oscillator Frequency
–
–
1.5
–
MHz
Drain-Source On-State
Resistance
ISW = 100mA High Side
–
250
–
mΩ
ISW = 100mA Low Side
–
170
–
mΩ
Output Discharge Switch On
Resister
–
–
2.1
–
KΩ
VENH
EN Threshold High
–
1.5
–
–
V
VENL
EN Threshold Low
–
–
–
0.4
V
EN Leakage Current
VIN= VEN =5V
-1.0
–
1.0
µA
VUVLO
Input UVLO Threshold
–
–
2.4
2.7
V
VHYS
UVLO Hysteresis
–
–
0.1
–
V
TOTP
Over Temperature Protection
–
–
+160
–
°C
TOTH
OTP Hysteresis
–
–
+15
–
°C
tSS
Soft-start Time
–
–
2
–
ms
VIN
VOUT
NEW PRODUCT
Parameter
RDS(ON)
RDISCH
IEN
AP3428/A
Document number: DS37417 Rev. 2 - 2
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AP3428/A
Performance Characteristics (@TA = +25°C, VIN = 5V, VOUT = 1.8V, unless otherwise specified.)
Efficiency vs. Load Current
Feedback Reference Voltage vs. Temperature
0.630
90
0.625
Feedback Reference Voltage（V）
100
80
Efficiency(%)
60
50
40
30
VIN=5V, VOUT=1.0V
20
VIN=5V, VOUT=1.8V
10
VIN=5V, VOUT=3.3V
0
10
100
1000
0.615
0.610
0.605
0.600
0.595
0.590
0.585
0.580
0.575
0.570
-60
-40
-20
0
PFET Drain-Source On-State Resistance vs. Temperature
40
60
80
100
120
140
NFET Drain-Source On-State Resistance vs. Temperature
260
240
240
220
220
200
NFETRdson（mohm）
PFET Rdson （mohm）
20
Temperature（oC）
Output Current(mA)
200
180
160
180
160
140
120
140
100
120
100
-60
80
-60
-40
-20
0
20
40
60
80
100
120
-20
0
20
40
60
80
100
120
140
Temperatrue（oC）
Oscillation Frequency vs. Temperature
100
1.8
90
1.7
Oscillation Frequency（MHz）
80
70
60
50
40
30
20
10
0
-60
-40
140
Temperature（oC）
Quiescent Current vs. Temperature
Quiescent Current（uA）
NEW PRODUCT
70
0.620
-40
-20
0
20
40
60
80
100
120
140
Temperatrue（oC）
AP3428/A
Document number: DS37417 Rev. 2 - 2
1.6
1.5
1.4
1.3
1.2
1.1
1.0
-60
-40
-20
0
20
40
60
80
100
120
Temperature（oC）
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140
AP3428/A
Performance Characteristics (@TA = +25°C, VIN = 5V, VOUT = 1.8V, unless otherwise specified.)
Enable Turn on Characteristic (IOUT=1A)
Enable Turn off Characteristic (IOUT=1A)
EN
(5V/div
)
EN
(5V/div)
NEW PRODUCT
VOUT
(1V/div)
VOUT
(1V/div)
IL
(1A/div)
IL
(1A/div)
SW
(5V/div)
SW
(5V/div)
Time (2ms/div)
Time (2ms /div)
Short Current Protection (IOUT=1A)
SCP Recovery (IOUT=1A)
VOUT
(1V/div)
VOUT
(1V/div)
IL
(1A/div)
IL
(1A/div)
SW
(5V/div)
SW
(5V/div)
Time (2ms /div)
Time (2ms/div)
Load Transient (IOUT=0.1A to 1A)
VOUT_AC
(100mV/div
)
Load Transient (IOUT=0.5A to 1A)
VOUT_AC
(100mV/div)
IO
(1A/div)
IO
(1A/div)
Time (2ms/div)
AP3428/A
Document number: DS37417 Rev. 2 - 2
Time (2ms /div)
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AP3428/A
Application Information
Typical application circuit is shown in the Typical Applications Circuit and for the circuit parameters setting please refers to the following
descriptions.
Under Voltage Lockout (UVLO) Circuit
When the VIN drops lower than the UVLO detector threshold, the UVLO circuit starts to operate, V REF stops, and high-side switch and low-side
switch built-in switch transistors turn “OFF”. As a result, V OUT drops according to the COUT capacitance value and the load. When the V IN is rising
NEW PRODUCT
higher than UVLO released voltage, the IC will restart the operation.
Short Circuit Protection and Recovery
When the AP3428/A output node is shorted to GND that VFB drops under 0.42V, AP3428/A will enter hiccup mode to protect itself. If short circuit is
removed, and VFB rises over 0.42V, the AP3428/A recovers to normal operation again. If the AP3428/A reaches OCP threshold while short circuit,
the AP3428/A will enter cycle by cycle current limit mode until the current under OCP threshold.
Over Temperature Protection
The internal thermal temperature protection circuitry is provided to protect the integrated circuit in the event that the maximum junction
temperature is exceeded. When the junction temperature exceeds +160°C, it shuts down the internal control circuit and switching power MOSFET.
The AP3428/A will restart automatically under the control of soft start circuit when the junction temperature decreases to +145°C.
Setting the Output Voltage
The output voltage can be adjusted from 1 to 5V using an external resistor divider. Table 1 shows a list of resistor selections for common output
voltages. Resistor R1 is selected based on a design tradeoff between efficiency and output voltage accuracy. For high values of R1 there is less
current consumption in the feedback network. However the tradeoff is output voltage accuracy due to the bias current in the error amplifier. R1 can
be determined by the following equation. Meanwhile, the input capacitor should close to IC for preventing unexpected influences.
Out Voltage
1.0V
1.2V
1.5V
1.8V
2.5V
2.8V
3.3V
LX
C1
R1
FB
R2
Figure 1. Feedback Divider Network
AP3428/A
Document number: DS37417 Rev. 2 - 2
R1
91k
100k
150k
300k
380k
440k
430k
R2
120k
100k
100k
150k
120k
120k
100k
C1
22pf
22pf
22pf
22pf
22pf
22pf
22pf
Table 1. Resistor Selection for Common Output
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AP3428/A
Ordering Information
AP3428X X X – X
NEW PRODUCT
Product Name
Package
Product Version
Package
Packing
RoHS/Green
A : AP3428A
Blank : AP3428
KT : TSOT25
DN : U-DFN2020-6
TR : Tape & Reel
G1 : Green
Temperature Range
Part Number
Marking ID
Packing
AP3428AKTTR-G1
L2J
3000/Tape & Reel
AP3428KTTR-G1
L2H
3000/Tape & Reel
AP3428DNTR-G1
CQ
3000/Tape & Reel
TSOT25
-40 to +85°C
U-DFN2020-6
(Type J)
AP3428/A
Document number: DS37417 Rev. 2 - 2
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AP3428/A
Marking Information
(1)
TSOT25 for AP3428
(Top View)
NEW PRODUCT
First Line: Logo and Marking ID
(2)
TSOT25 for AP3428A
(Top View)
First Line: Logo and Marking ID
(3)
U-DFN2020-6 (Type J)
(Top View)
First Line: Logo and Marking ID
AP3428/A
Document number: DS37417 Rev. 2 - 2
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AP3428/A
Package Outline Dimensions
(1)
Package Type: TSOT25
D
e1
01(4x)
E1/2
NEW PRODUCT
E/2
E1
c
E
Gauge Plane
0
L
L2
01(4x)
b
e
Seating Plane
A2
A1
A
Seating Plane
(2)
TSOT25
Dim
Min
Max
Typ
A
1.00
A1
0.01 0.10
A2
0.84 0.90
b
0.30 0.45
c
0.12 0.20
D
2.90
E
2.80
E1
1.60
e
0.95 BSC
e1
1.90 BSC
L
0.30 0.50
L2
0.25 BSC
θ
0°
8°
4°
θ1
4°
12°
All Dimensions in mm
Package Type: U-DFN2020-6 (Type J)
A3
A A1
Seating Plane
D
D2
D2/2
0
.10
R0
E2/2
E E2
U-DFN2020-6
(Type J)
Dim
Min
Max Typ
A
0.50 0.60
-A1
0.00 0.05 0.03
A3
--0.203
b
0.20 0.30 0.25
D
1.95 2.075 2.00
D2
1.45 1.65 1.55
E
1.95 2.075 2.00
E2
0.76 0.96 0.86
e
0.65 BSC
L
0.30 0.40 0.35
All Dimensions in mm
L
e
AP3428/A
Document number: DS37417 Rev. 2 - 2
b
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AP3428/A
Suggested Pad Layout
(1)
Package Type: TSOT25
NEW PRODUCT
C
Dimensions Value (in mm)
C
0.950
X
0.700
Y
1.000
Y1
3.199
Y1
Y
X
(2)
Package Type: U-DFN2020-6 (Type J)
X1
C
G
Dimensions
Y2
Y1
Y
C
G
X
X1
Y
Y1
Y2
Value
(in mm)
0.650
0.120
0.350
1.650
0.550
0.960
2.300
X
AP3428/A
Document number: DS37417 Rev. 2 - 2
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AP3428/A
IMPORTANT NOTICE
NEW PRODUCT
DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT,
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
trademark rights, nor the rights of others. Any Customer or user of this document or products described herein in such applications shall assume
all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on Diodes Incorporated
website, harmless against all damages.
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Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and
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indirectly, any claim of personal injury or death associated with such unintended or unauthorized application.
Products described herein may be covered by one or more United States, international or foreign patents pending. Product names and markings
noted herein may also be covered by one or more United States, international or foreign trademarks.
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.
LIFE SUPPORT
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
information or support that may be provided by Diodes Incorporated. Further, Customers must fully indemnify Diodes Incorporated and its
representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems.
Copyright © 2016, Diodes Incorporated
www.diodes.com
AP3428/A
Document number: DS37417 Rev. 2 - 2
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