FSEZ1216 Fairchild Semiconductor, FSEZ1216 Datasheet - Page 11

• Manufacturer Part Number: FSEZ1216
• Description: The primary-side PWM integrated Power MOSFET, FSEZ1216, significantly simplifies power supply design that requires CV and CC regulation capabilities
• Manufacturer: Fairchild Semiconductor

© 2009 Fairchild Semiconductor Corporation
FSEZ1216 • Rev. 1.0.1
Cable Voltage Drop Compensation
When it comes to cellular phone charger applications,
the actual battery is located at the end of cable, which
causes, typically, several percent of voltage drop on the
actual battery voltage. FSEZ1216 has a programmable
cable voltage drop compensation, which provides a
constant output voltage at the end of the cable over the
entire load range in CV mode. As load increases, the
voltage drop across the cable is compensated by
increasing the reference voltage of voltage regulation
error amplifier. The amount of compensation is
programmed by the resistor on the COMR pin. The
relationship between the amount of compensation and
the COMR resistor is shown in Figure 26.
Temperature Compensation
Built-in temperature compensation provides constant
voltage regulation over wide a range of temperature
variation.
compensates the forward-voltage drop variation of the
secondary-side rectifier diode.
Green-Mode Operation
The FSEZ1216 uses voltage regulation error amplifier
output (V
modulates the PWM frequency, as shown in Figure 27,
such that the switching frequency decreases as load
decreases. In heavy load conditions, the switching
frequency is fixed at 42KHz. Once V
below 2.8V, the PWM frequency starts to linearly
decrease from 42KHz to 550Hz to reduce the switching
losses. As V
frequency is fixed at 550Hz and FSEZ1216 enters deep
green mode, where the operating current reduces to
1mA, further reducing the standby power consumption.
15
14
13
12
11
10
Figure 26. Cable Voltage Drop Compensation
9
8
7
6
5
4
3
2
1
10
COMV
This
COMV
) as an indicator of the output load and
20
decreases below 0.8V, the switching
30
internal
40
R
COMR
50
(k )
compensation
60
70
COMV
80
decreases
90
current
100
11
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. FSEZ1216 has an internal frequency
hopping circuit that changes the switching frequency
between 39.4kHz and 44.6kHz with a period of 3ms, as
shown in Figure 28.
42kHz
42.0kHz
550H z
44.6kHz
39.4kHz
Switching Frequen cy
Figure 27. Switching Frequency in Green Mode
Green
Mode
Dee p
Gate Drive Signal
f
s
Figure 28. Frequency Hopping
0.8V
t
t
t
s
s
s
Green Mode
3ms
2.8V
Normal Mode
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V
COMV
t