February 2012

Doc ID 17811 Rev 2

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SRK2000

Synchronous rectifier smart driver for LLC resonant converters

Features

controller optimized for LLC resonant

converters

and startup condition

1 A source and 3.5 A sink drive current

Applications

Description

The SRK2000 smart driver implements a control

scheme specific to secondary-side synchronous

rectification in LLC resonant converters that use a

transformer with center-tap secondary winding for

full-wave rectification.

It provides two high-current gate-drive outputs,

each capable of driving one or more N-channel

Power MOSFETs. Each gate driver is controlled

separately and an interlocking logic circuit

prevents the two synchronous rectifier MOSFETs

from conducting simultaneously.

The control scheme in this IC allows for each

synchronous rectifier to be switched on as the

corresponding half-winding starts conducting and

switched off as its current goes to zero. A unique

feature of this IC is its intelligent automatic sleep-

mode. It allows the detection of a low-power

operating condition for the converter and puts the

IC into a low consumption sleep-mode where gate

driving is stopped and quiescent consumption is

reduced. In this way, converter efficiency

improves at light load, where synchronous

rectification is no longer beneficial. The IC

automatically exits sleep-mode and restarts

switching as it recognizes that the load for the

converter has increased.

A noticeable feature is the very low external

component count required.

Figure 1.

Internal block diagram

Table 1.

Device summary

Order code

Package

Packing

SRK2000D

SO-8

Tube

SRK2000DTR

Tape and reel

SO-8

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