Diodes AP3433 User Manual

3A, 2MHz High Performance Synchronous Buck Converter AP3433

Preliminary Datasheet

General Description

The AP3433 is a 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 two N-channel power
MOSFETs with low on-resistance. Current mode
control provides fast transient response and
cycle-by-cycle current limit.

The switching frequency of AP3433 can be
programmable from 300kHz to 2MHz, which allows
small-sized components, such as capacitors and
inductors. A standard series of inductors from several
different manufacturers are available. This feature
greatly simplifies the design of switch-mode power
supplies.

Under voltage lockout is internally set at 2.6V, but
can be increased by programming the threshold with
a resistor network on the enable pin. The output
voltage startup ramp is controlled by the soft-start pin.
An open drain power good signal indicates the output
is within 93% to 107% of its nominal voltage.

The AP3433 is available in QFN-3×3-16 package.

Features

• Input Voltage Range: 2.95V to 5.5V

• 0.827V Reference Voltage with ±3% Precision

• Two 45mΩ(typical) MOSFETs for High
Efficiency at 3A Load

• High Efficiency: up to 94%

• Output Current: 3A

• Programmable Frequency:300kHz to 2MHz

• Current Mode Control

• Synchronizes to External Clock

• Adjustable Soft-start

• Soft Start-up into Pre-biased Output

• UV and OV Power Good Output

• Built-in Over Current Protection

• Built-in Thermal Shutdown Function

• Programmable UVLO Function

• Built-in Over Voltage Protection

• Thermally Enhanced 3mm×3mm 16-pin QFN

Applications

• Low-voltage, High-density Power Systems

• Point of Load Regulation for Consumer
Applications such as Set Top Boxes, LCD
Displays, CPE Equipment

QFN-3×3-16

Figure 1. Package Type of AP3433

Jul. 2012 Rev. 1. 1 BCD Semiconductor Manufacturing Limited

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Preliminary Datasheet

3A, 2MHz High Performance Synchronous Buck Converter AP3433

Pin Configuration

FN Package

(QFN-3×3-16)

Pin 1 Mark

13141516

VIN

1
2

VIN

GND

3
49

GND

EP

5678

SW

12

SW

11

SW

10

SS

Figure 2. Pin Configuration of AP3433 (Top View)

Pin Description

Pin Number Pin Name Function

1,2,16 VIN

3,4 GND

5 AGND

6 FB Feedback pin. Inverting node of the transconductance error amplifier

7 COMP

8 RT/CLK Resistor timing or external clock input pin

9 SS

10,11,12 SW

Supply input pin. A capacitor should be connected between the VIN and GND
pin to keep the DC input voltage constant

Power ground. This pin should be electrically connected to the power pad under
the IC

Analog ground. This pin should be electrically connected to GND close to the
device

Compensation pin. This pin is the output of the transconductance error amplifier
and the input to the current comparator. Connect external compensation elements
to this pin to stabilize the control loop

Soft-start pin. An external capacitor connected to this pin sets the output voltage
rise time. This pin can also be used for tracking

Internal power switch output pin. This pin is connected to the inductor and
bootstrap capacitor

Bootstrap pin. A bootstrap capacitor is connected between the BOOT pin and SW

13 BOOT

pin. The voltage across the bootstrap capacitor drives the internal high-side power
MOSFET

14 PGD

Power good indicator output. Asserts low if output voltage is low due to thermal
shutdown, over-current, over/under-voltage or EN shut down

Enable pin, internal pull-up current source. Pull below 1.2V to disable. Float to

15 EN

enable. Can be used to set the on/off threshold (adjust UVLO) with two additional
resistors

Jul. 2012 Rev. 1. 1 BCD Semiconductor Manufacturing Limited

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Preliminary Datasheet

3A, 2MHz High Performance Synchronous Buck Converter AP3433

Functional Block Diagram

Figure 3. Functional Block Diagram of AP3433

Ordering Information

AP3433 -

Circuit Type

Package

FN: QFN-3

Package

QFN-3×3-16 -40 to 85ºC AP3433FNTR-G1 B1D Tape & Reel

Temperature

×3-16

Range

Part Number Marking ID Packing Type

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

Jul. 2012 Rev. 1. 1 BCD Semiconductor Manufacturing Limited

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G1: Green

TR: Tape & Reel

Preliminary Datasheet

3A, 2MHz High Performance Synchronous Buck Converter AP3433

Absolute Maximum Ratings (Note 1)

Parameter Symbol Value Unit

VIN Pin Voltage VIN -0.3 to 6.5 V

EN Pin Voltage VEN -0.3 to 6.5 V

SW Pin Voltage VSW -0.3 to VIN+0.3 V

FB Pin Voltage VFB -0.3 to 6.5 V

COMP Pin Voltage V

PGD Pin Voltage V

RT/CLK Pin Voltage V

SS Pin Voltage VSS -0.3 to 6.5 V

Thermal Resistance
(Junction to Ambient)
Thermal Resistance
(Junction to Case)

Operating Junction Temperature TJ -40 to 125 ºC

Storage Temperature T

Lead Temperature (Soldering, 10sec) T

ESD (Machine Model) 200 V

ESD (Human Body Model) 2000 V

θ

JC (BOTTOM)

-0.3 to 6.5 V

COMP

-0.3 to 6.5 V

PGD

-0.3 to 6.5 V

RT/ CLK

θ

JA

-65 to 150 ºC

STG

260 ºC

LEAD

70 ºC/W

5 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 2.95 5.5 V

Maximum Output Current I

Operating Ambient Temperature TA -40 85 ºC

OUT(MAX)

3 A

Jul. 2012 Rev. 1. 1 BCD Semiconductor Manufacturing Limited

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