特性 Features

? Secondary side synchronous rectification

controller optimized for flyback converter

? Suitable for QR and mixed CCM/DCM fixed

frequency operation

? Wide Vcc operating voltage range 3.75 to 32 V

? CC regulation operation down to 2 V output

supported

? Very low quiescent current in low consumption

mode (160 μA)

? High-voltage sensing input for SR MOSFET

drain-source voltage (100 V AMR)

? Operating frequency up to 300 kHz

? High-current gate-drive output for N-MOSFET

? Fast turn-on with minimum delay time and

adaptive turn-off logic

? Programmable min. TON and fixed min. TOFF (3

options: SRK1000, SRK1000A, SRK1000B)

? Low consumption mode entry by primary side

burst-mode detection or by detection of SR

MOSFET conduction lower than programmed

min TON

? SOT23-6L package

Applications

? Battery chargers / quick chargers

? Adapters

? USB power delivery (profile 3)

描述 Description

The SRK1000 is a controller intended for

secondary side synchronous rectification (SR) in

flyback converters, suitable for operation in QR

and mixed CCM/DCM fixed frequency circuits.

It provides a high-current gate-drive output,

capable of driving N-channel Power MOSFETs.

The control scheme of this IC is such that the SR

MOSFET is switched on as soon as current starts

flowing through its body diode and it is then

switched off as current approaches zero.

The fast turn-on, with minimum delay, and the

innovative adaptive turn-off logic allow

maximizing the conduction time of the SR

MOSFET and eliminating the effect of parasitic

inductance in the circuit.

The device enters low consumption mode when it

detects primary controller burst-mode operation,

or when the SR MOSFET conduction becomes

lower than the programmed minimum TON. In this

way, converter efficiency improves at light load

where synchronous rectification is no longer

beneficial.

After the converter restarts switching or the IC

detects that the current conduction in the rectifiers

has increased 20 above the min TON

programmed value, the IC exits low consumption

mode and resumes switching operation.