SG6902 Fairchild Semiconductor, SG6902 Datasheet - Page 3

no-image

SG6902

Manufacturer Part Number
SG6902
Description
Green-Mode PFC / Flyback-PWM Controller
Manufacturer
Fairchild Semiconductor
Datasheet
www.DataSheet4U.com
Green-Mode PFC / Flyback-PWM Controller
PIN DESCIRPTIONS
© System General Corp.
Version 1.3.1 (IAO33.0022.B3)
Name
VRMS
RI
OTP
IEA
IPFC
IMP
ISENSE
FBPWM
IPWM
AGND
SS
OPWM
GND
OPFC
VDD
RANGE
OVP
FBPFC
VEA
IAC
Pin No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Type
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
PFC Output Voltage Control
PFC Over-Voltage Input
Voltage Feedback Input for
PFC
Error Amplifier Output for
PFC Voltage Feedback Loop
Input AC Current
Function
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 V
Reference setting. One resistor connected between RI and AGND determines the
switching frequency. The switching frequency is equal to [1560 / RI] kHz, where RI is
in kΩ. For example, if R
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
SG6902 is disabled.
This is the output of the PFC current error amplifier. The signal from this pin is
compared with an internal sawtooth and determines the pulse width for PFC gate
drive.
The inverting input of the PFC current error 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 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 resistor. An external opto-coupler from secondary feedback circuit is
usually 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 start-up, the SS pin charges an external capacitor with a 50µA (R
constant-current source. The voltage on FBPWM is clamped by SS during start-up. In
the event of a protection condition occurring and/or PWM being disabled, the SS pin
quickly discharges.
The totem-pole output drive for the flyback PWM MOSFET. This pin is internally
clamped under 18V to protect the
Power ground.
The totem-pole output drive for the PFC MOSFET. This pin is internally clamped
under 18V to protect the
The power supply pin.
Two-level output voltage setting for PFC. The PFC output voltage at low line can be
reduced to improve efficiency. The RANGE pin is of high impedance while the V
voltage is lower than a threshold.
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.
Before start-up, this input is used to provide start-up current for V
operation, this input is used to provide current reference for the multiplier.
- 3 -
I
is 24kΩ, the switching frequency is 65kHz.
MOSFET.
www.sg.com.tw • www.fairchildsemi.com
MOSFET.
RMS
voltage drops below a threshold.
Product Specification
September, 2007
DD
. For normal
SG6902
I
=24kΩ)
RMS

Related parts for SG6902