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AP6508

500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER

AP6508

Document number: DS33437 Rev. 5 - 2

1 of 14

www.diodes.com

October 2011

NEW PRODUCT

Description

The AP6508 is a 500kHz switching frequency internal

compensated synchronous DCDC buck converter. It has

integrated compensation, and low R

DSON

high and low side

MOSFETs.

The AP6508 enables continues load current of up to 3A with

efficiency as high as 93%.

The AP6508 features current mode control operation, which

enables fast transient response times and easy loop

stabilization.

The AP6508 has external programmable softstart and a

Power Good indicator enabling sequencing and ramp control.

The AP6508 simplifies board layout and reduces space

requirements with its high level of integration and minimal

need for external components, making it ideal for distributed

power architectures.

The AP6508 is available in a standard Green DFN4030-14

package with exposed PAD for improved thermal

performance and is RoHS compliant.

Pin Assignments

BST

AGND

GND

DFN4030-14

Exposed Pad

(Top View)

VCC

Features

• V

4.5V to 21V

• V

OUT

adjustable to 0.8V

• 500kHz switching frequency

• Enable pin

• External Softstart

• Power Good

• Protection

o OCP

o Thermal Shutdown

• Lead Free Finish/ RoHS Compliant (Note 1)

Applications

• Gaming Consoles

• TV sets and Monitors

• Set Top Boxes

• Distributed power systems

• Home Audio

• Consumer electronics

Note: 1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied. Please visit our website at

http://www.diodes.com/products/lead_free.html.

Typical Application Circuit

100

LOAD CURRENT (A)

Efficiency vs. Load Current

V = 12V

V = 5V

L = 3.3µH

OUT

IEN

(%)

Summary of content (14 pages)

PAGE 1
AP6508 500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER Description Pin Assignments The AP6508 is a 500kHz switching frequency internal compensated synchronous DCDC buck converter. It has integrated compensation, and low RDSON high and low side MOSFETs. (Top View) The AP6508 features current mode control operation, which enables fast transient response times and easy loop stabilization. The AP6508 has external programmable softstart and a Power Good indicator enabling sequencing and ramp control.
PAGE 2
AP6508 500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER Pin Descriptions Name Description Supply Voltage. The AP6508 operates from a 4.5V to 21V input rail. C1 is needed to decouple the input rail. Use wide PCB trace to make the connection. 1 IN 2,3,4,5 SW Switch Output. Use wide PCB trace to make the connection. 6 BST Bootstrap. A capacitor connected between SW and BS pins is required to form a floating supply across the high-side switch driver. 7 EN EN=1 to enable the chip.
PAGE 3
AP6508 500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER Absolute Maximum Ratings (Note 2) Symbol VIN Supply Voltage VSW Switch Node Voltage VBS VFB VEN Rating Unit 22 V -0.3 to 23 V Bootstrap Voltage VSW + 6 V Feedback Voltage –0.3V to +6 V Enable/UVLO Voltage –0.3V to +6 V Comp Voltage –0.
PAGE 4
AP6508 500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER Electrical Characteristics (VIN = 12V, TA = +25°C, unless otherwise noted) NEW PRODUCT Symbol Parameter Test Conditions IIN Shutdown Supply Current VEN = 0V IIN Supply Current (Quiescent) VEN = 2.0V, VFB = 1.0V RDS(ON)1 High-Side Switch On-Resistance (Note 6) RDS(ON)2 Low-Side Switch On-Resistance (Note 6) SWLKG Switch Leakage Current VEN = 0V, VSW = 0V ILimit Current Limit FSW Oscillator Frequency VFB = 0.
PAGE 5
AP6508 500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER Typical Performance Characteristics 20 SHUTDOWN SUPPLY CURRENT (µA) QUIESCENT SUPPLY CURRENT (mA) 1.25 1.2 1.15 1.1 1.05 1 0 18 16 14 12 10 8 6 4 2 0 0 5 10 15 20 25 INPUT VOLTAGE Quiescent Supply Current vs. Input Voltage 5 10 15 20 25 INPUT VOLTAGE (V) Shutdown Supply Current vs. Input Voltage 7 5.05 VIN = 12V VOUT = 1.2V 6.8 5.045 CURRENT LIMIT (A) 6.6 VCC (V) 5.04 5.035 5.03 6.4 6.2 6 5.8 5.6 5.4 5.025 5.02 5.
PAGE 6
AP6508 500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER Typical Performace Characteristics (cont.) 100 100 VOUT = 1.2V VOUT = 1.8V EFFICIENCY (%) EFFICIENCY (%) 90 80 70 60 50 80 70 60 50 VIN = 12V VIN = 5V 40 0 VIN = 12V VIN = 5V 2 1 LOAD CURRENT (A) Efficiency vs. Load Current 40 3 100 2 1 LOAD CURRENT (A) Efficiency vs. Load Current 3 0 2 1 LOAD CURRENT (A) Efficiency vs. Load Current 3 90 90 EFFICIENCY (%) 0 100 VOUT = 2.
PAGE 7
AP6508 500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER Typcal Performance Characteristics NEW PRODUCT VIN = 12V, VOUT = 1.2V, L = 3.3µH, C1 = 22µF, C2 = 47µF, TA = +25°C, unless otherwise noted. Time- 2µs/div Steady State Test IOUT = 3A Time- 200µs/div Load Transient Test IOUT = 1.5A to 3A. Step at 0.
PAGE 8
AP6508 500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER Typcal Performance Characteristics NEW PRODUCT VIN = 12V, VOUT = 1.2V, L = 3.3µH, C1 = 22µF, C2 = 47µF, TA = +25°C, unless otherwise noted. Time- 1µs/div Input Voltage Ripple Time- 2µs/div Output Voltage Ripple 90% of VFB 72% of VFB Time- 1us/div Powergood Rising Threshold AP6508 Document number: DS33437 Rev. 5 - 2 Time- 1µs/div Powergood FallingThreshold 8 of 14 www.diodes.
PAGE 9
AP6508 500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER NEW PRODUCT Application Information Theory of Operation Enable The AP6508 is a 3A current mode, synchronous buck regulator with built in power MOSFETs. current mode control assures excellent line and load regulation and a wide loop bandwidth for fast response to load transients. Figure. 2 depicts the functional block diagram of AP6508. The enable (EN) input allows the user to control turning on or off the converter.
PAGE 10
AP6508 500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER Application Information (cont.) NEW PRODUCT External Soft Start Soft start is traditionally implemented to prevent the excess inrush current. This in turn prevents the converter output voltage from overshooting when it reaches regulation. The AP6508 has an internal current source with a soft start capacitor to ramp the reference voltage from 0V to 0.807V. The soft start time is internally fixed at 2ms (TYP).
PAGE 11
AP6508 500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER Application Information (cont.) Peak current determines the required saturation current rating, which influences the size of the inductor. Saturating the inductor decreases the converter efficiency while increasing the temperatures of the inductor and the internal MOSFETs. Hence choosing an inductor with appropriate saturation current rating is important.
PAGE 12
AP P6508 50 00kHz 21V 3A SYNCH HRONOUS S DC/DC BU UCK CONV VERTER Ordering Information n NEW PRODUCT AP650 08 FE - 13 Package Packing FE E : DFN4030 13 : Tape & Ree el 13” Tape T and Reel Pa art Number Suffix Device e Pac ckage Code Pa ackaging (Note 7) Qu uantity AP6508FE E-13 FE F DFN N4030-14 3000/Ta ape & Reel Note: -13 7. Pad layout as shown on Diodes Inc. sugg gested pad layout document d AP02001 1, which can be fou und on our website at http://www.diodes.com m/datasheets/ap020 001.
PAGE 13
AP6508 500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER NEW PRODUCT Tape Orientation (Note 8) Note: 8. The taping orientation of the other package type can be found on our website at http://www.diodes.com/datasheets/ap02007.pdf AP6508 Document number: DS33437 Rev. 5 - 2 12 of 14 www.diodes.
PAGE 14
AP6508 500kHz 21V 3A SYNCHRONOUS DC/DC BUCK CONVERTER IMPORTANT NOTICE 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).