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Datasheet: SG6902 (System General)

Green mode PFC/Forward PWM Controller

 

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Product Specification

Green-mode PFC/Flyback-PWM Controller
SG6902
ęSystem General Corp. - 2 - www.sg.com.tw
Version 1.1(IAO33.0022.B1) Feb.22, 2006
FEATURES
Green-mode PFC and PWM operation
No switching of PFC at light loads for the best
power saving
Low start-up and operating current
Innovative Switching-Charge
multiplier-divider
Multi-vector control for improved PFC output
transient response
Interleaved PFC/PWM switching
Programmable two-level PFC output voltage
Average-current-mode control for PFC
Cycle-by-cycle current limiting for PFC/PWM
PFC over-voltage and under-voltage protections
PFC and PWM feedback open-loop protection
Brownout protection
Over-temperature protection

APPLICATIONS
Switching Power Suppliers with Active PFC
High-Power Adaptors

DESCRIPTION
The highly integrated SG6902 is specially
designed for power supplies consist of boost PFC and
Flyback PWM. It requires very few external
components to achieve green-mode operation and
versatile protections. It is available in 20-pin SOP
and SSOP packages.
The patented interleave-switching feature
synchronizes the PFC and PWM stages and reduces
switching noise. At light loads, the switching
frequency is continuously decreased to reduce power
consumption. If output loading is further reduced, the
PFC stage is turned off to further reduce power
consumption.
For PFC stage, the proprietary multi-vector
control scheme provides a fast transient response in a
low-bandwidth PFC loop, in which the overshoot and
undershoot of the PFC voltage are clamped. If the
feedback loop is broken, the SG6902 will shut off
PFC to prevent extra-high voltage on output.
Programmable two-level output voltage control will
reduce the PFC output voltage at low line input to
increase the efficiency of the power supply.
For the Flyback PWM, the synchronized slope
compensation ensures the stability of the current loop
under continuous-conduction-mode operation.
Built-in line-voltage compensation maintains
constant output-power limit. Hiccup operation during
output overloading is also guaranteed.
In addition, SG6902 provides complete
protection functions such as brownout protection and
RI pin open/short protections.
TYPICAL APPLICATION
Product Specification

Green-mode PFC/Flyback-PWM Controller
SG6902
ęSystem General Corp. - 3 - www.sg.com.tw
Version 1.1(IAO33.0022.B1) Feb.22, 2006
MARKING DIAGRAM PIN CONFIGURATION




ORDERING INFORMATION
Part Number
Package
SG6902SZ
20-pin SOP(Lead Free)
SG6902RZ
20-pin SSOP(Lead Free)
PIN DESCIRPTIONS
Name Pin
No.
Type
Function
VRMS 1
Line-voltage
Detection
Line-voltage detection. The pin is used for PFC multiplier, RANGE control of PFC output
voltage, brownout protection .For brownout protection, the controller will be disabled after
a delay time when the VRMS voltage drops below a threshold.
RI 2 Oscillator
Setting
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
k
. For example, if RI is equal to 24k, then the switching frequency will be 65 kHz.
OTP 3
Over Temperature
Protection
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 will be disabled.
IEA 4
Output for PFC
Current Amplifier
This is the output of the PFC current error amplifier. The signal from this pin will be
compared with an internal saw-tooth and hence determine the pulse width for PFC gate
drive.
IPFC 5
Inverting Input for
PFC Current
Amplifier
The inverting input of the PFC current error amplifier. Proper external compensation
circuits will result in excellent input power factor via average-current-mode control.
IMP 6
Non-inverting Input
for PFC Current
Amplifier
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.
ISENSE 7
Peak Current Limit
Setting for PFC
The peak-current setting for PFC.
T
: S= SOP ,R = SSOP
P :
Z =Lead Free
+ ROHS Compatible
Null=regular package
XXXXXXXX
: Wafer Lot
Y
: Year;
WW
: Week
V
: Assembly Location
SG6902 TP
XXXXXXXXYWWV
Product Specification

Green-mode PFC/Flyback-PWM Controller
SG6902
ęSystem General Corp. - 4 - www.sg.com.tw
Version 1.1(IAO33.0022.B1) Feb.22, 2006
FBPWM 8
PWM Feedback
Input
The control input for voltage-loop feedback of PWM stage. It is internally pulled high
through a resistor. Usually an external opto-coupler from secondary feedback circuit is
connected to this pin.
IPWM
9
PWM Current Sense
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.
AGND 10 Ground
Signal
Ground
SS
11
PWM Soft Start
During startup, the SS pin will charge an external capacitor with a 50uA (RI=24k
)
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.
OPWM
12
PWM Gate Drive
The totem-pole output drive for the Flyback PWM MOSFET. This pin is internally
clamped under 18V to protect the MOSFET
.
GND 13 Ground
Power
Ground
OPFC
14
PFC Gate Drive
The totem-pole output drive for the PFC MOSFET. This pin is internally clamped under
18V to protect the MOSFET
.
VDD
15
Supply
The power supply pin.
RANGE
16
PFC Output-voltage
Control
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 VRMS
voltage is lower than a threshold.
OVP 17
PFC Over Voltage
Input
The PFC stage over voltage input. The comparator will disable 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.
FBPFC 18
Voltage Feedback
Input for PFC
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.
VEA 19
Error-Amp Output
for PFC Voltage
Feedback Loop
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.
IAC
20
Input AC Current
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.
Product Specification

Green-mode PFC/Flyback-PWM Controller
SG6902
ęSystem General Corp. - 5 - www.sg.com.tw
Version 1.1(IAO33.0022.B1) Feb.22, 2006
BLOCK DIAGRAM
Product Specification

Green-mode PFC/Flyback-PWM Controller
SG6902
ęSystem General Corp. - 6 - www.sg.com.tw
Version 1.1(IAO33.0022.B1) Feb.22, 2006
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter
Test
Conditions
Value
Unit
V
DD
DC Supply Voltage*
25
V
I
AC
Input AC Current
2
mA
V
HIGH
OPWM, OPFC, IAC
-0.5 to +25V
V
V
LOW
Others
-0.5 to +7V
V
P
D
Power Dissipation
At T
A
< 50░C
0.8
W
T
J
Operating Junction Temperature
-40 to +125
T
STG
Storage Temperature Range
-55 to +150
SOP 35.44
R
j-C
Thermal resistance (Junction to Case)
SSOP 39.6
/W
SOP 230
T
L
Lead Temperature (soldering 10sec)
SSOP 230
ESD capability, HBM model
4.5
KV
ESD
ESD capability, Machine model
250
V
*All voltage values, except differential voltages, are given with respect to GND pin.
*Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device.
RECOMMENDED OPERATING JUNCTION TEMPERATURE :-30 ~ 85*
*For proper operation
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