SG6905 Fairchild Semiconductor, SG6905 Datasheet - Page 3

• Manufacturer Part Number: SG6905
• Manufacturer: Fairchild Semiconductor

Green mode PFC/Flyback-PWM Controller
PIN DESCRIPTIONS
© System General Corp.
Version 1.1.1 (IAO33.0060.B1)
Name
VRMS
RI
OTP
IEA
IPFC
IMP
ISENSE
FBPWM
IPWM
AGND
SS
OPWM
GND
OPFC
VDD
RDY
PFC_ON
FBPFC
VEA
IAC
Pin No. Type
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Line-Voltage
Detection
Oscillator Setting
Over Temperature
Protection
Output for PFC
Current Amplifier
Inverting Input for
PFC Current
Amplifier
Non-inverting Input
for PFC Current
Amplifier
Peak Current Limit
Setting for PFC
PWM Feedback
Input
PWM Current Sense
Ground
PWM Soft Start
PWM Gate Drive
Ground
PFC Gate Drive
Supply
Ready signal output
Remote On/Off
Voltage Feedback
Input for PFC
Error-Amp Output for
PFC voltage
feedback loop
Input AC Current
Function
Line voltage detection. The pin is used for PFC multiplier, brownout protection .For
brownout protection; the controller will be disabled after a delay time when the VRMS
voltage drops below a threshold voltage.
Reference setting. One resistor connected between RI and ground determines the
switching frequency. The switching frequency is equal to [1560 / RI] kHz, where RI is in
kΩ. For example, if RI is equal to 24kΩ, then the switching frequency will be 65 kHz.
This pin supplies an over temperature protection signal. A constant current is output from
this pin. An external NTC thermistor must be connected from this pin to ground. The
impedance of the NTC thermistor decreases whenever the temperature increases. Once
the voltage of the OTP pin drops below the OTP threshold, the SG6905 will be disabled.
This is the output of the PFC current amplifier. The signal from this pin will be compared
with an internal saw-tooth and hence determine the pulse width for PFC gate drive.
The inverting input of the PFC current amplifier. Proper external compensation circuits will
result in excellent input power factor via average-current-mode control.
The non-inverting input of the PFC current amplifier and also the output of multiplier.
Proper external compensation circuits will result in excellent input power factor via
average- current- mode control.
The peak-current setting for PFC.
The control input for voltage-loop feedback of PWM stage. It is internally pulled high
through a 6.5kΩ resistance. Usually an external opto-coupler from secondary feedback
circuit is connected to this pin.
The current-sense input for the Flyback PWM. Via a current sense resistor, this pin
provides the control input for peak-current-mode control and cycle-by-cycle current
limiting.
Signal Ground
During startup, the SS pin will charge an external capacitor with a 50µA (RI=24kΩ)
constant current source. The voltage on FBPWM will be clamped by SS during startup. In
the event of a protection condition occurring and/or PWM being disabled, the SS pin will
be quickly discharged.
The totem-pole output drive for the Flyback PWM MOSFET. This pin is internally
clamped under 17V to protect the
Power Ground
The totem-pole output drive for the PFC MOSFET. This pin is internally clamped under
17V to protect the
The power supply pin.
This pin outputs a ready signal to control the power on sequence. Once the SG6905 is
turned on and the FBPFC(PFC Feedback input)voltage is higher than 2.7V, will lock this
pin to high impedance. Disable the SG6905 Will reset this pin to the low.
The PFC stage will disabled whenever the voltage at this pin is exceed 2.45V.
The feedback input for PFC voltage loop. The inverting input of PFC error amp. This pin is
connected to the PFC output through a divider network.
The error-amp output for PFC voltage feedback loop. A compensation network (usually a
capacitor) is connected between this pin and ground. A large capacitor value will result in
a narrow bandwidth and hence improve the power factor.
Before start-up, this input is used to provide startup current for VDD. For normal
operation, this input is used to provide current reference for the multiplier.
MOSFET.
- 3 -
MOSFET.
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Product Specification
September 27, 2007
SG6905