1 Description
The iW671 is a high performance synchronous rectifier controller with an integrated MOSFET driver for flyback converters operating at discontinuous conduction mode. Combined with the MOSFET, the iW671 can emulate the diode rectifier at the secondary side of the flyback to reduce conduction loss. The iW671 determines the timing of the driver by sensing the voltage across the RDS(ON) to achieve lossless sensing. The iW671 uses proprietary digital adaptive turnoff control technology to minimize the turn-off deadtime of the synchronous rectifier so that the parallel Schottky diode
required by conventional synchronous rectifiers can be eliminated. The integrated driver has strong driving capability for high efficiency. The operating power consumption of the controller excluding the driver is less than 4mW at no load to achieve the ultra-low no-load power consumption for 5V applications. The iW671 integrates a pulse linear regulator to maintain the operation of the synchronous rectifier at low system output voltage when the system is operating in constant current (CC) mode.
The iW671 also integrates the adaptive voltage position monitor to detect the flyback converter output voltage undershoot, enabling faster recovery from standby. Dialog’s iW1766C1 primary-side controllers are optimized to work with the iW671 for very low output ripple, fast dynamic load response (DLR), and very low no-load power consumption (< 15mW) at 230VAC input in a typical 5V, 2.5A power supply.
2 Features
● Digital adaptive turn-off control minimizes deadtime
and eliminates the parallel Schottky diode
● Integrated pulse linear regulator (PLR) allows SR
operation at low system output voltage down to 2V in
typical 5V, 2.5A USB charger applications
● Wide input operating voltage up to 30V
● Optimized 5V MOSFET gate driver
● Intelligent low power management achieves ultra-low
no-load operating current < 0.65mA
● Lossless MOSFET VDS sensing for SR timing control
● Integrated adaptive voltage position monitor for fast
flyback output voltage undershoot detection
● 8-pin SOIC and 8-pin MSOP packages
3 Applications
● Compact AC/DC adapters/chargers for media tablets and smart phones