FAN6749 Fairchild Semiconductor, FAN6749 Datasheet - Page 3

• Manufacturer Part Number: FAN6749
• Description: The FAN6749 highly integrated PWM controller enhances the performance of flyback converters
• Manufacturer: Fairchild Semiconductor

© 2012 Fairchild Semiconductor Corporation
FAN6749 • Rev. 1.0.0
Marking Information
Pin Configuration
Pin Definitions
Pin #
1
2
3
4
5
6
7
8
SENSE
Name Description
GATE
GND
VDD
NC
HV
RT
FB
Ground Pin. A 0.1µF decoupling capacitor between VDD and GND is recommended.
Feedback Pin. The output voltage feedback information from the external compensation circuit is
fed into this pin. The PWM duty cycle is determined by comparing the FB signal with current-
sense signal from the SENSE pin.
No connection
High-Voltage Startup. The HV pin is typically connected to the AC line input through an external
diode and a resistor (R
also to sense the line voltage. The line voltage information is used for brown-out protection and
power limit line compensation.
Over-Temperature Protection. An external NTC thermistor is connected from this pin to the
GND pin. Once the voltage of the RT pin drops below the threshold voltage, the controller latches
off the PWM. The RT pin also provides external latch protection. If the RT pin is not connected to
an NTC resistor for over-temperature protection, place a 100kΩ resistor to ground to prevent
noise interference.
Current Sense. The sensed voltage is used for peak-current-mode control, over-current
protection, short-circuit protection, and cycle-by-cycle current limiting.
Power Supply of IC. A holdup capacitor typically connects from this pin to ground. A rectifier
diode in series with the transformer auxiliary winding connects to this pin to supply bias during
normal operation.
Gate Drive Output. The totem-pole output driver for the power MOSFET; internally limited to
V
GATE-CLAMP
ZXYTT
6749ML
TM
.
Figure 4. Pin Configuration (Top View)
GND
NC
HV
FB
HV
). This pin is used not only to charge V
Figure 3. Top Mark
1
2
3
4
3
8
7
6
5
F - Fairchild Logo
Z - Plant Code
X - 1-Digit Year Code
Y - 1-Digit Week Code
TT - 2-Digit Die Run Code
T - Package Type (M=SOP)
M - Manufacture Flow Code
SENSE
GATE
VDD
RT
DD
capacitor during startup, but
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