Diodes AP3408 User Manual

2A, 4MHz High Efficiency Synchronous Buck Converter AP3408

Preliminary Datasheet

General Description

The AP3408 is a current mode, PWM synchronous
buck DC/DC converter, capable of driving a 2A load
with high efficiency, excellent line and load
regulation. It operates in continuous PWM mode.

The AP3408 integrates synchronous P-channel and
N-channel power MOSFET switches with low
on-resistance. It is ideal for portable applications
powered from a single Li-ion battery. 100% duty
cycle and low on-resistance P-channel internal power
MOSFET can maximize the battery life.

The switching frequency of AP3408 can be
programmable from 300kHz to 4MHz, which allows
small-sized components, such as capacitors
inductors
different manufacturers are available. This feature
greatly simplifies the design of switch-mode power
supplies.

The AP3408 is available in DFN-3×3-10 and PSOP-8
packages.

A standard series of inductors from several

.

and

Features

Input Voltage Range: 2.6 to 5.5V

•

• Adjustable Output from 0.8 to 5V

• 0.8V Reference Voltage with ± 2% Precision

• Output Current: 2A

• High Efficiency up to 95%

• Low R

• Programmable Frequency: 300kHz to 4MHz

• Current Mode Control

• Forced Continuous-mode Operation

• 100% Duty Cycle

• Synchronizable Switching Frequency

Power Good Output Voltage Monitoring

•

• Built-in Soft-start

• Built-in Short Circuit Protection

• Built-in Thermal Shutdown Protection

• Built-in Current Limit Function

Internal Switches

DSON

Applications

• Portable Media Player

• Digital Still and Video Cameras

• Notebook

DFN-3×3-10 PSOP-8

Figure 1. Package Types of AP3408

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Preliminary Datasheet

2A, 4MHz High Efficiency Synchronous Buck Converter AP3408

Pin Configuration

DN Package MP Package

(DFN-3×3-10) (PSOP-8)

SHDN/ RT

SYNC

GND

SW

PGND

Pin 1 Mark

1

2

Exposed Pad

3

Connected to

4

56

PGND

10

9

8

7

COMP
FB

PGOOD
VDD
PVDD

SHDN/RT

Figure 2. Pin Configuration of AP3408 (Top View)

COMP

1

GND

2

Exposed Pad
Connected to

SW

3

PGND PVDD

4

PGND

8

FB

7

VDD

6

5

Pin Description

Pin Number

DFN-3×3-10 PSOP-8

1 1 SHDN/RT

2 SYNC

3 2 GND

4 3 SW

5 4 PGND

6 5 PVDD

7 6 VDD

8 PGOOD

9 7 FB

10 8 COMP

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Pin Name Description

Oscillator resistor input. Connect a resistor to GND from
this pin to set the switching frequency. Forcing this pin to
V

to shutdown the device

DD

External clock synchronization input. The oscillation
frequency can be synchronized to an external oscillation
applied to this pin. When tied to VDD, the internal
oscillator is selected
Signal ground. All small-signal ground, such as the
compensation components and the exposed pad should be
connected to this pin, which in turn connects to PGND at
one point
Internal power switch output. Connect this pin with one
terminal of the inductor
Power ground. Connect this pin as close as possible to CIN
and COUT
Power input supply. Decouple this pin to PGND with a
capacitor
Signal input supply. Decouple this pin to GND with a
capacitor. Normally V

is equal to V

DD

Power Good Indicator. Open-drain logic output that is
pulled to ground when the output voltage is not within ±

12.5% of regulation point
Feedback voltage. This pin is the inverting input of internal
error amplifier. It senses the converter output voltage
through an external resistor divider. The internal reference
voltage is 0.8V, which determines the output voltage
through the resistor divider
Compensation input. This pin is the output of internal error
amplifier. Connect external compensation elements to this
pin to stabilize the control loop

BCD Semiconductor Manufacturing Limited

2

PVDD

Preliminary Datasheet

2A, 4MHz High Efficiency Synchronous Buck Converter AP3408

Functional Block Diagram

SHDN/RT

SYNC

2

SD

1(1)

CS

6(5)

PVDD

COMP

FB

PGOOD

A for DFN-3X3-10

B for PSOP-8

10(8)

9(7)

8

A (B)

0.8V

Oscillator

EA

Clamp

SS

0.4V

0.7V

0.9V

SUM

PWM
Control

Logic

V

REF

7(6)

VDD

Figure 3. Functional Block Diagram of AP3408

OCP

OTPUVLO

Driver

DC

4(3)

SW

5(4)

PGND

3(2)

GND

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Preliminary Datasheet

2A, 4MHz High Efficiency Synchronous Buck Converter AP3408

Ordering Information

AP3408 -

G1: Green

Circuit Type

Package
DN: DFN-3×3-10
MP: PSOP-8

TR: Tape & Reel
Blank: Tube

Package

DFN-3×3-10

PSOP-8

Temperature

Range

-40 to 125°C

Part Number Marking ID

Green Green

AP3408DNTR-G1 BFA Tape & Reel
AP3408MP-G1 3408MP-G1 Tube
AP3408MPTR-G1 3408MP-G1 Tape & Reel

Packing

Type

BCD Semiconductor's Pb-free products, as designated with "G1" suffix in the part number, are RoHS compliant
and green.

Absolute Maximum Ratings (Note 1)

Parameter Symbol Value Unit

VDD Pin Voltage VDD -0.3 to 6 V
PVDD Pin Voltage V

-0.3 to 6 V

PVDD

FB Pin Voltage VFB -0.3 to 6 V
COMP Pin Voltage V

-0.3 to 6 V

COMP

SW Pin Voltage VSW -0.3 to VIN+0.3 V
SHDN/RT Pin Voltage V

Thermal Resistance

DFN-3×3-10
PSOP-8 75

SHDN/RT

-0.3 to 6 V

θ

JA

110

ºC/W

Operating Junction Temperature TJ 150 ºC
Storage Temperature T
Lead Temperature (Soldering, 10 sec) T

-65 to 150 ºC

STG

260 ºC

LEAD

ESD (Machine Model) 200 V
ESD (Human Body Model) 2000 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 periods may affect device reliability.

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µ

Preliminary Datasheet

2A, 4MHz High Efficiency Synchronous Buck Converter AP3408

Recommended Operating Conditions

Parameter Symbol Min Max Unit

Input Voltage VIN 2.6 5.5 V
Maximum Output Current I
Operating Junction Temperature TJ -40 125 ºC

OUT (MAX)

2 A

Electrical Characteristics

VIN=V

DD =VPVDD

=3.3V, TA=25℃, unless otherwise specified.

Parameters Symbol Conditions Min Typ Max Unit
INPUT SECTION

Input Voltage Range VDD 2.6 5.5 V

=0.75V,

V

Supply Current IQ

Shutdown Supply Current I
Under Voltage Threshold

Lockout
Under Voltage Hysteresis
Lockout

SHDN

V

V

HUVLO

UVLO

FB

No Switching
Shutdown,

VDD Rising 2.2 V

300 mV

V

=5.5V

IN

460

1

µA

µA

FEEDBACK SECTION
Feedback Voltage VFB 0.784 0.8 0.816 V

FB Pin Bias Current IFB 0.1 0.4
Current Sense Transresistance RT 0.2

V

Switching Leakage Current
Error Gain Amplifier Voltage GV 800
Error1Amplifier1Trans-conductance GS 800

SHDN/RT=VIN

=5.5V

1

µA

Ω

µA

A

/V

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Preliminary Datasheet

2A, 4MHz High Efficiency Synchronous Buck Converter AP3408

Electrical Characteristics (Continued)

VIN=V

DD =VPVDD

=3.3V, T

=25℃, unless otherwise specified.

A

Parameters Symbol Conditions Min Typ Max Unit

OSCILLATOR SECTION

RT Pin Voltage VRT 0.8 V

Switching Frequency f

Maximum Duty Cycle D

R

=330kΩ

OSC

MAX

OSC

ADJ Frequency 0.3 4 MHz

VFB=0.75V 100 %

0.8 1 1.2 MHz

POWER SWITCH SECTION
Switch Current Limit I

Internal P-FET On
Resistance
Internal N-FET On
Resistance

R

R

SHDN/RT SECTION
Shutdown Threshold

PGOOD SECTION
PGOOD Voltage Range

PGOOD Pull Down
Resistance

TOTAL DEVICE

Output Current I
Output Voltage Line

Regulation
Output Voltage Load
Regulation

Soft-start Time tSS
Thermal Shutdown

Temperature

T

Thermal Shutdown
Temperature Hysteresis

VFB=0.75V 2.2 3.8 A

LIMIT

ISW=500mA 0.11 0.16

PDSON

ISW=-500mA 0.11 0.17

NDSON

Ω

Ω

VDD-0.7 VDD-0.4 V

±12.5 ±15 %
120

=2.6 to 5.5V

V

OUT

LNR

LOD I

OTSD

T

HYS

DD

=2.5V

V

OUT

=2.7 to 5.5V

V

DD

=100mA

I

OUT

=0.01 to 2A

OUT

I

＝10mA

OUT

2 A

0.4 %/V

±0.2 %

1.5 ms

160 ºC

20 ºC

Ω

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Preliminary Datasheet

2A, 4MHz High Efficiency Synchronous Buck Converter AP3408

Typical Performance Characteristics

VIN=V

DD =VPVDD

=3.3V, TA=25℃, unless otherwise specified.

600

500

400

300

Supply Current (µA)

200

100

2.53.03.54.04.55.05.56.0

Figure 4. Supply Current vs. Input Voltage

100

90

80

70

60

Efficiency (%)

50

40

30

0 500 1000 1500 2000 2500

Figure 6. Efficiency vs. Output Current Figure 7. PMOS ON Resistance vs.

700

600

500

VFB=0.75V

Input Voltage (V )

400

300

Supply Current (µA)

200

100

-60 -30 0 30 60 90 120 150

Ambient Temperature (oC)

Figure 5. Supply Current vs. Ambient T emperature

140

120

100

80

PMOS ON Resistance (mΩ)

60

-60 -30 0 30 60 90 120 150

Ambient Temperature (oC)

Output Current (mA)

V

OUT

=2.5V

VIN=3.3V
VIN=5.0V

Ambient Temperature

VIN=3.3V
V

=0.75V

FB

VIN=3.3V

=0.75V

V

FB

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Preliminary Datasheet

2A, 4MHz High Efficiency Synchronous Buck Converter AP3408

Typical Performance Characteristics (Continued)

VIN=V

DD =VPVDD

=3.3V, TA=25℃, unless otherwise specified.

140

120

100

80

NMOS ON Resistance (mΩ)

60

-60 -30 0 30 60 90 120 150

Ambient Temperature (oC)

VIN=3.3V
V

FB

=0.85V

1.2

1.1

1.0

0.9

Frequency (MHz)

0.8

0.7

-60 -30 0 30 60 90 120 150

Ambient Temperature (OC)

Figure 8. NMOS ON Resistance vs. Figure 9. Frequency vs. Ambient Temperature

Ambient Temperature

R

=330k

OSC

V

=3.3V

IN

=2.5V

V

OUT

0.9

0.8

(V)
V

0.7

FB

0.6

0.5

-60 -30 0 30 60 90 120 150

Ambient Temperature (OC)

Figure 10. V

FB

VIN=3.3V

=2.5V

V

OUT

5.0

4.5

4.0

3.5

Current Limit (A)

3.0

2.5

-40 0 40 80 120 160

VIN=3.3V

Temperature (OC)

vs. Ambient Temperature Figure 11. Current Limit vs. Ambie nt Temperature

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Preliminary Datasheet

2A, 4MHz High Efficiency Synchronous Buck Converter AP3408

T ypical Application

Figure 12. Typical Application of AP3408

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Preliminary Datasheet

2A, 4MHz High Efficiency Synchronous Buck Converter AP3408

Mechanical Dimensions

DFN-3×3-10 Unit: mm(inch)

0.300(0.012)

0.500(0.020)

PIN #1 IDENTIFICATION

See DETAIL A

N1

DETAIL A

0.700(0.028)

0.800(0.031)

2.900(0.114)

3.100(0.122)

Pin 1 Mark

0.000(0.000)

0.050(0.002)

2.900(0.114)

3.100(0.122)

1.600(0.063)

1.800(0.071)

0.200(0.008)

0.300(0.012)

0.500(0.020)
TYP

N6 N10

2.300(0.090)

2.500(0.098)

N5

0.153(0.006)

0.253(0.010)

12

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Pin 1 options

12

Preliminary Datasheet

2A, 4MHz High Efficiency Synchronous Buck Converter AP3408

Mechanical Dimensions (Continued)

PSOP-8 Unit: mm(inch)

3.202(0.126)

3.402(0.134)

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BCD Semiconductor Manufacturing Limited

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particular purpose, nor does BCD Semiconductor Manufacturing Limited assume any liability arising out of the application or use

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