Gate Drive

1-m

UCC24636

Secondary

Current

Gate Drive

VDS Sensing

Driver

5 A

300 ns

15 A

5 Ps

0.85 A

DRV

CS

VDD

GND

VS

VAC

FB

UCC28740

HV

TL431

UCC24636

VPC

DRV

GND

TBLK

VSC

VDD

5

1

4

6

2

3

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Design

An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,

intellectual property matters and other important disclaimers. PRODUCTION DATA.

UCC24636

SLUSCG2A – MARCH 2016 – REVISED MARCH 2016

UCC24636 Synchronous Rectifier (SR) Controller

With Ultra-Low Standby Current

1

1 Features

1

•

Secondary-Side SR Controller Optimized for 5-V

to 24-V Output Discontinuous/Transition Mode

Only Flyback Converters

•

Volt-Second Balance Control Enables Highest

Rectifier Efficiency

•

Compatible with PSR and SSR Flyback

Controllers

•

Ultra Low 110-µA Standby Current Consumption

•

Auto-Detect Standby Mode Disables SR Switching

for Lower No-Load Power Consumption

•

Inductance

•

Operating Frequency Up to 130 kHz

•

Wide VDD Range from 3.6 V to 28 V

•

Adaptive Gate Drive Clamp

•

Open and Short Pin Fault Protection

2 Applications

•

AC/DC Adapters For Smartphones and Tablets

•

USB Chargers with Type-C Connectors

•

Notebook and Ultrabook Adapters

•

High Efficiency Flyback Converters in Industrial

SMPS

•

High Efficiency Auxilliary Power In Server and

Desktop Applications

3 Description

The UCC24636 SR is a compact, 6-pin secondary-

side synchronous rectifier MOSFET controller and

driver for high efficiency Flyback converters operating

in Discontinuous (DCM) and Transition mode (TM).

Unlike traditional SR controllers which measure the

SR MOSFET drain voltage, UCC24636 implements a

volt-second balance control method to determine the

turn off transition of the SR MOSFET; hence, SR

conduction time is independent of the MOSFET

flexibility to designers in component slelction and

PCB layout. This control method enables maximum

SR conduction time and highest rectifier efficiency for

a given MOSFET.

The controller has built in intelligence to detect

converter no load operation and automatically enters

standby mode. While in standby mode, it disables the

SR MOSFET and lowers its bias supply current to

110uA to further reduce overall system standby

power consumption. The wide VDD operating range

for the controller allows direct bias from the converter

output for fixed or variable output voltage designs.

This eliminates the need for an auxilliary winding on

the main transformer, which simplifies the circuit

design and reduces the cost.

Device Information(1)

PART NUMBER

PACKAGE

BODY SIZE (NOM)

UCC24636

SOT23 (6)

2.92 mm x 1.30 mm

(1) For all available packages, see the orderable addendum at

the end of the data sheet.

Simplified Schematic

Gate-Drive Timing vs VDS Sensing SR Driver