FSEZ1016A View Datasheet(PDF) - Fairchild Semiconductor
Part Name
Description
Manufacturer
FSEZ1016A Datasheet PDF : 16 Pages
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Temperature Compensation
Built-in temperature compensation provides constant
voltage regulation over a wide range of temperature
variation. This internal compensation current
compensates the forward-voltage drop variation of the
secondary-side rectifier diode.
Green-Mode Operation
The FSEZ1016A uses voltage regulation error amplifier
output (VCOMV) as an indicator of the output load and
modulates the PWM frequency, as shown in Figure 26,
such that the switching frequency decreases as load
decreases. In heavy-load conditions, the switching
frequency is fixed at 43KHz. Once VCOMV decreases
below 2.8V, the PWM frequency starts to linearly
decrease from 43KHz to 550Hz to reduce the switching
losses. As VCOMV decreases below 0.8V, the switching
frequency is fixed at 550Hz and FSEZ1016A enters
“deep green” mode, where the operating current drops
to 1mA, reducing the standby power consumption.
Gate Drive Signal
ts
ts
ts
fs
45.6kHz
43.0kHz
40.4kHz
Swi tching Frequen cy
43 kH z
3ms
t
Figure 27. Frequency Hopping
Dee p
G ree n
Mod e
Green Mod e
Normal Mod e
550H z
0.8V
2.8V
V COMV
Figure 26. Switching Frequency in Green Mode
Leading-Edge Blanking (LEB)
At the instant the MOSFET is turned on, there is a high-
current spike through the MOSFET, caused by primary-
side capacitance and secondary-side rectifier reverse
recovery. Excessive voltage across the RCS resistor can
lead to premature turn-off of the MOSFET. FSEZ1016A
employs an internal leading-edge blanking (LEB) circuit
to inhibit the PWM comparator for a short time after the
MOSFET is turned on. External RC filtering is not required.
Frequency Hopping
EMI reduction is accomplished by frequency hopping,
which spreads the energy over a wider frequency range
than the bandwidth measured by the EMI test
equipment. FSEZ1016A has an internal frequency-
hopping circuit that changes the switching frequency
between 40.4kHz and 45.6kHz with a period of 3ms, as
shown in Figure 27.
Startup
Figure 28 shows the typical startup circuit and
transformer auxiliary winding for a FSEZ1016A
application. Before FSEZ1016A begins switching, it
consumes only startup current (typically 10μA) and the
current supplied through the startup resistor charges the
VDD capacitor (CDD). When VDD reaches turn-on voltage
of 16V (VDD-ON), FSEZ1016A begins switching, and the
current consumed increases to 3.5mA. Then, the power
required for FSEZ1016A is supplied from the
transformer auxiliary winding. The large hysteresis of
VDD provides more hold-up time, which allows using a
small capacitor for VDD.
VDL
+
Np
CDL
-
RSTART
DDD
AC line
CDD
NA
FSEZ1016A
1
CS
DRAIN 8
2 GND
RS1
3
COMI
6
VDD
4
COMV
5
VS
RS2
Figure 28. Startup Circuit
© 2009 Fairchild Semiconductor Corporation
FSEZ1016A • Rev. 1.0.2
11
www.fairchildsemi.com
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