© 2015 Exar Corporation

XR76203/5/8

3A/5A/8A Synchronous Step Down COT Regulator

exar.com/XR76203/5/8

Rev 1A

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General Description

The XR76203, XR76205 and XR76208 are synchronous step-down regu-

lators combining the controller, drivers, bootstrap diode and MOSFETs in

a single package for point-of-load supplies. The XR76203, XR76205 and

XR76208 have load current ratings of 3A, 5A and 8A respectively. A wide

5V to 40V input voltage range allows for single supply operation from

industry standard 24V ±10%, 18V-36V, and rectified 18VAC and 24VAC

rails.

With a proprietary emulated current mode Constant On-Time (COT) con-

trol scheme, the XR76203, XR76205 and XR76208 provide extremely

fast line and load transient response using ceramic output capacitors.

They require no loop compensation, simplifying circuit implementation

and reducing overall component count. The control loop also provides

0.07% load and 0.15% line regulation and maintains constant operating

frequency. A selectable power saving mode allows the user to operate in

discontinuous conduction mode (DCM) at light current loads thereby sig-

nificantly increasing the converter efficiency.

A host of protection features, including over-current, over-temperature,

short-circuit and UVLO, helps achieve safe operation under abnormal

operating conditions.

The XR76203/5/8 are available in a RoHS-compliant, green/halogen-free

space-saving QFN 5x5mm package.

FEATURES



Controller, drivers, bootstrap diode and

MOSFETs integrated in one package



3A, 5A and 8A Step Down Regulators



Wide 5V to 40V Input Voltage Range





Proprietary Constant On-Time Control



No Loop Compensation Required



Stable Ceramic Output Capacitor Operation



Programmable 200ns to 2μs On-Time



Constant 100kHz to 800kHz Frequency



Selectable CCM or CCM/DCM



CCM/DCM for high efficiency at light-load



CCM for constant frequency at light-load



Programmable Hiccup Current Limit with

Thermal Compensation



Precision Enable and Power Good flag



Programmable Soft-start



30-pin 5x5mm QFN package

APPLICATIONS



Distributed Power Architecture



Point-of-Load Converters



Power Supply Modules



FPGA, DSP, and Processor Supplies



Base Stations, Switches/Routers, and Servers

Ordering Information – back page

Typical Application

3.260

3.270

3.280

3.290

3.300

3.310

3.320

3.330

3.340

5

10

152025

3035

40

PGND

FB

ILIM

SW

BST

XR76208

VIN

EN/MODE

PGOOD

VCC

SS

TON

AGND

Enable/Mode

Power Good

R

L1

R1

R2

XR76205

PVIN

XR76203

Line Regulation