SG6901 Fairchild Semiconductor, SG6901 Datasheet - Page 5

• Manufacturer Part Number: SG6901
• Description: The highly integrated SG6901A is designed for power supplies with boost PFC and flyback PWM
• Manufacturer: Fairchild Semiconductor

© 2008 Fairchild Semiconductor Corporation
SG6901A • Rev. 1.0.2
Pin Definitions
Pin #
10
11
12
13
14
15
16
17
18
19
20
1
2
3
4
5
6
7
8
9
FBPWM
ISENSE
RANGE
OPWM
FBPFC
Name
VRMS
AGND
IPWM
OPFC
IPFC
GND
VDD
OVP
OTP
VEA
IMP
IEA
IAC
SS
RI
Description
Line voltage detection. The pin is used for PFC multiplier, RANGE control of PFC output
voltage, and brownout protection. For brownout protection, the controller is disabled after a
delay time when the VRMS voltage drops below a threshold.
Reference setting. One resistor connected between RI and ground determines the switching
frequency. The switching frequency is equal to [1560 / RI] KHz, where R
if R
Over-temperature protection. 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 SG6901A is disabled.
PFC current amplifier output. The signal from this pin is compared with an internal sawtooth
to determine the pulse width for PFC gate drive.
The inverting input of the PFC current amplifier. Proper external compensation circuits result
in excellent input power factor via average-current-mode control.
The non-inverting input of the PFC current amplifier and the output of multiplier. Proper
external compensation circuits results in excellent input power factor via average-current-mode
control.
Current limit. A resistor from this pin to GND sets the current limit.
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.
Soft start. During startup, the SS pin charges an external capacitor with a 50µA (R
constant current source. The voltage on FBPWM is clamped by SS during startup. In the event
of a protection condition occurring and/or PWM being disabled, the SS pin is quickly
discharged.
The totem-pole output drive for the flyback PWM MOSFET. This pin is internally clamped under
17V to protect the MOSFET.
Power ground.
The totem-pole output drive for the PFC MOSFET. This pin is internally clamped under 17V
to protect the MOSFET.
The power supply pin.
The RANGE pin has high impedance whenever the V
The PFC output voltage at low line can be reduced to improve efficiency.
The PFC stage over-voltage input. The comparator disables the PFC output driver if the
voltage at this input exceeds a threshold. This pin can be connected to FBPFC or it can be
connected to the PFC boost output through a divider network.
The feedback input for PFC voltage loop. The inverting input of PFC error amplifier. This pin
is connected to the PFC output through a divider network.
The error amplifier output for PFC voltage feedback loop. A compensation network (usually
a capacitor) is connected between this pin and ground. A large capacitor value results in a
narrow bandwidth and improves the power factor.
This input is used to provide current reference for the multiplier.
I
is equal to 24KΩ, the switching frequency is 65KHz.
5
RMS
voltage is lower than a threshold.
I
is in KΩ. For example,
I
=24KΩ)
www.fairchildsemi.com