1. General description

The NEX81801DA and NEX81802DA

(NEX81801/2DA) are high performance synchronous

rectification controllers used in switching mode power

supplies. It supports operation in Discontinuous

Conduction Mode (DCM), Continuous Conduction

Mode (CCM) and quasi-resonant flyback converters.

The NEX81801/2DA regulates the forward drop

voltage of an external synchronous rectifier (SR)

MOSFET in two stages. This allows the SR FET to turn

off quickly when the VDS becomes positive.

The externally adjustable turn-on blanking time can

effectively prevent the synchronous rectifier from

being falsely turned off due to leakage inductance and

parasitic parameter oscillation.

The adaptive turn-on detection circuit can prevent

the SR from being mistakenly turned on when the

VDS DCM oscillation crosses zero during some load

conditions. The adaptive turn-on detection circuit also

enhances SR conduction efficiency during light load

conditions, thereby improving the average efficiency of

the power supply across the entire load range.

The synchronous switch can be configured at high-side

or low-side output without auxiliary windings or other

power sources, because the NEX81801/2DA has a

self-supply capability.

The NEX81801/2DA uses TSOT23-6 packaging with

low thermal resistance. This can effectively reduce the

junction temperature of the chip, making it suitable for

high-density power supply design.

2. Features and benefits

? Supports DCM, CCM, QR operation

? Supports up to 800 kHz switching frequency

? Standard and logic level MOSFET driving capability

? Wide output range down to 0 V with 2-channel VCC

supply

? No need for auxiliary winding for high-side or lowside

rectification

? Smart proportional gate driver for fast SR turn-off at

CCM

? Adjustable turn-on blanking time for increased

noise immunity

? Proprietary adaptive turn-on detection prevents SR

FET from falsely turning on during DCM operation

? 10 ns typical turn-off propagation delay

? Available in a TSOT23-6 FC package

? ESD protection:

? HBM: ANSI/ESDA/JEDEC JS-001 class 2

exceeds 2000 V

? CDM: ANSI/ESDA/JEDEC JS-002 class C2a

exceeds 500 V

3. Applications

? USB PD/QC chargers

? AC/DC adapters for portable devices

? Flyback SMPS with high-efficiency requirements