Diodes AP3418 User Manual
AP3418
Document number: DS37233 Rev. 2 - 2
1 of 11
www.diodes.com
April 2014
© Diodes Incorporated
AP3418
A Product Line of
Diodes Incorporated
Description
The AP3418 is a 1.4MHz fixed frequency, current mode, PWM
synchronous buck (step-down) DC-DC converter, capable of driving a
1.5A load with high efficiency, excellent line and load regulation. The
device integrates synchronous P-channel and N-channel power
MOSFET switches with low on-resistance. It is ideal for powering
portable equipment that runs from a single Li-ion battery.
A standard series of inductors are available from several different
manufacturers optimized for use with the AP3418. This feature greatly
simplifies the design of switch-mode power supplies.
The AP3418 is available in SOT25 package.
Features
Input Voltage Range: 2.5V to 5.5V
Output Voltage: 0.6V to VIN
ADJ Output
Fixed 1.4MHz Frequency
High Efficiency up to 95%
Output Current: 1.5A
Current Mode Control
100% Duty Cycle in Dropout
Built-in Over Current Protection
Built-in Short Circuit Protection
Built-in Thermal Shutdown Protection
Built-in UVLO Function
Built-in Soft-start
Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)
Halogen and Antimony Free. “Green” Device (Note 3)
Pin Assignments
(Top View)
SOT25
Applications
LCD TV
Set-top Box
Datacom
Portable Device
Smart Phone
AP3418-ADJ
L
C
OUT
C
IN
V
IN
R2 R1
V
OUT
4.7F
2.2H
22F
EN
VIN
SW
FB
GND
1
4
3
2
5
1
2
3 4
5
EN
GND
SW
FB
VIN
1.5A, 1.4MHz High Efficiency Synchronous DC-DC Buck Converter
Notes: 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.
Typical Applications Circuit
AP3418
Document number: DS37233 Rev. 2 - 2
2 of 11
www.diodes.com
April 2014
© Diodes Incorporated
AP3418
A Product Line of
Diodes Incorporated
Pin Number
Pin Name
Function
1
EN
Control input pin. Forcing this pin above 1.5V enables the IC. Forcing this
pin below 0.4V shuts down the IC. When the IC is in shutdown mode, all
functions are disabled to decrease the supply current below 1µA
2
GND
Ground pin
3
SW
Power switch output pin. Inductor connection to drain of the internal PFET
and NFET switches
4
VIN
Supply input pin. Bypass to GND with a 4.7µF or greater ceramic
capacitor
5
FB
This is the feedback pin of the device. Connect this pin directly to the
output if the fixed output voltage version is used. For the adjustable
version, an external resistor divider is connected to this pin
VOLTAGE
REFERENCE
OSCILLATOR
CURRENT
SENSE
ERROR
AMPLIFIER
PWM
COMPARATOR
MAX
CURRENT LIMIT
0.6V
V
OCP
0.4V
LOGIC
CLK
DRIVER
SHORT
CIRCUIT
PROTECTION
REVERSE
COMPARATOR
EN
FB
GND
SW
GNDVIN
VIN
1
5
2
4
3
4
2
Pin Descriptions
Functional Block Diagram
AP3418
Document number: DS37233 Rev. 2 - 2
3 of 11
www.diodes.com
April 2014
© Diodes Incorporated
AP3418
A Product Line of
Diodes Incorporated
Symbol
Parameter
Rating
Unit
VIN
Input Voltage
-0.3 to 6.0
V
VFB
Feedback Voltage
-0.3 to VIN +0.3
V
VEN
EN Pin Voltage
-0.3 to VIN+0.3
V
VSW
SW Pin Voltage
-0.3 to VIN+0.3
V
θ
JA
Thermal Resistance
265
ºC/W
TJ
Operating Junction Temperature
+150
ºC
T
STG
Storage Temperature
-65 to +150
ºC
T
LEAD
Lead Temperature (Soldering, 10sec)
+260
ºC
–
ESD(Machine Model)
200
V
–
ESD(Human Body Model)
2000
V
Symbol
Parameter
Min
Max
Unit
VIN
Input Voltage
2.5
5.5
V
TA
Operating Ambient Temperature
-40
+85
ºC
Absolute Maximum Ratings (Note 4)
Note 4: 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
AP3418
Document number: DS37233 Rev. 2 - 2
4 of 11
www.diodes.com
April 2014
© Diodes Incorporated
AP3418
A Product Line of
Diodes Incorporated
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
VIN
Input Voltage
–
2.5 – 5.5
V
IQ
Quiescent Current
V
FB
= 0.65V
–
62
100
µA
I
STBY
Shutdown Supply Current
V
EN
= GND
–
0.1 1 µA
V
REF
Reference Voltage
For Adjustable Output
Voltage
0.588
0.6
0.612
V
I
FB_H
Feedback Bias Current
V
FB
= 1V
-0.1 – 0.1
µA
I
FB_L
V
FB
= 0V
-0.1 – 0.1
R
DS(ON)_ P
PMOSFET RON
ISW = 200mA
–
0.2 – Ω
R
DS(ON) _N
NMOSFET RON
ISW = -200mA
–
0.15 – Ω
I
LIM
Switch Current Limit
V
FB
= 0.55V
1.8
2.3 – A
VH
EN Pin Threshold
–
1.5 – –
V
VL
– – –
0.4
V
UVLO
UVLO Threshold
VIN Rising
–
2.3
–
V
V
HYS
UVLO Hysteresis
– – 0.2
–
f
OSC
Oscillator Frequency
–
1.12
1.40
1.68
MHz
D
MAX
Max. Duty Cycle
–
100 – –
%
D
MIN
Min. Duty Cycle
– – –
0
I
SW_H
SW Leakage Current
VSW = 0V
–
0.1
–
µA
I
SW_L
VSW = 5V
–
0.1
–
tSS
Soft-start Time
– – 1 – ms
T
OTSD
Thermal Shutdown
– – +160 – ºC
T
HYS
Thermal Shutdown Hysteresis
– – +20 – ºC
Electrical Characteristics (V
= 5V, TA = +25ºC, unless otherwise specified.)
IN
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