NCP4303AMNTWG ON Semiconductor, NCP4303AMNTWG Datasheet - Page 20

• Manufacturer Part Number: NCP4303AMNTWG
• Description: Power Switch ICs - Power Distribution SEC SIDE SYNC RECT DRV
• Manufacturer: ON Semiconductor

Specifications of NCP4303AMNTWG

• Product Category: Power Switch ICs - Power Distribution

feature any internal filtering and reacts even on very narrow
voltage pulses. Thus it is wise to keep this input on a low
impedance path and provide it with a clean triggering signal.
is operated in deep CCM mode can be seen in Figure 47. In
this application the trigger signal is taken directly from the
flyback controller driver output and transmitted to the
secondary side by pulse transformer TR2. Because the
trigger input is rising edge sensitive, it is not necessary to
transmit the entire primary driver pulse to the secondary.
The coupling capacitor C5 is used to allow pulse transformer
core reset and also to prepare a needle pulse (a pulse with
width lower than 100 ns) to be transmitted to the NCP4303
trigger input. The advantage of needle trigger pulse usage is
that the required volt−second product of the pulse
transformer is very low and that allows the designer to use
very small and cheap magnetics. The trigger transformer can
Figure 47. Optional Application Schematic When NCP4303 is Used in CCM Flyback Converter and Trigger Input is
Note that the trigger input is an ultrafast input that doesn’t
A typical application schematic of a flyback converter that
Figure 46. Operating Waveforms for the Trig/Disable Input with a Trigger Signal that is Periodical and Overlaps
Implemented to Maximize Efficiency
CS (SR MOSFET Vds) High Level
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be for instance prepared on a small toroidal ferrite core with
diameter of 8 mm. Proper safety insulation between primary
and secondary sides can be easily assured by using triple
insulated wire for one or even both windings.
by external circuitry consisting of transistors Q1, Q2 and
surrounding components. The primary MOSFET is thus
turned−on with a slight delay so that the secondary
controller turns−off the SR MOSFET by trigger signal prior
to the primary switching. This method reduces the
commutation losses and the SR MOSFET drain voltage
spike, which results in improved efficiency.
additional capacitor with safety insulation) between the
primary and secondary to transmit the trigger signal. We do
not recommend this technique as the parasitic capacitive
currents between primary and secondary may affect the
trigger signal and thus overall system functionality.
The primary MOSFET gate voltage rising edge is delayed
It is also possible to use capacitive coupling (use