Product Specification
Green-mode PFC/Flyback-PWM Controller
SG6902
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.
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
TYPICAL APPLICATION
©System General Corp.
Version 1.2(IAO33.0022.B2)
-1-
www.sg.com.tw
Nov.17, 2006
Product Specification
Green-mode PFC/Flyback-PWM Controller
SG6902
PIN CONFIGURATION
MARKING DIAGRAM
SG6902TP
XXXXXXXXYWWV
T:
S= SOP ,R = SSOP
P :
Z =Lead Free
+ ROHS Compatible
Null=regular package
XXXXXXXX:
Wafer Lot
Y:
Year;
WW:
Week
V:
Assembly Location
ORDERING INFORMATION
Part Number
SG6902SZ
SG6902RZ
Package
20-pin SOP(Lead Free)
20-pin SSOP(Lead Free)
PIN DESCIRPTIONS
Name
VRMS
Pin No. Type
1
Line-voltage
Detection
Function
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.
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 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 SG6902 will be disabled.
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.
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.
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.
RI
2
Oscillator Setting
OTP
3
Over Temperature
Protection
Output for PFC
Current Amplifier
Inverting Input for
IEA
4
IPFC
5
PFC Current
Amplifier
Non-inverting Input
IMP
6
for PFC Current
Amplifier
Peak Current Limit
Setting for PFC
ISENSE
7
©System General Corp.
Version 1.2(IAO33.0022.B2)
-2-
www.sg.com.tw
Nov.17, 2006
Product Specification
Green-mode PFC/Flyback-PWM Controller
PWM Feedback
Input
SG6902
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.
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 50uA (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.
clamped under 18V to protect the MOSFET.
Power Ground
The totem-pole output drive for the PFC MOSFET. This pin is internally clamped under
18V to protect the MOSFET.
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 VRMS
voltage is lower than a threshold.
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.
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.
operation, this input is used to provide current reference for the multiplier.
For normal
This pin is internally
FBPWM
8
IPWM
AGND
SS
9
10
11
PWM Current Sense
Ground
PWM Soft Start
OPWM
GND
OPFC
VDD
RANGE
12
13
14
15
16
PWM Gate Drive
Ground
PFC Gate Drive
Supply
PFC Output-voltage
Control
PFC Over Voltage
Input
Voltage Feedback
Input for PFC
Error-Amp Output
for PFC Voltage
Feedback Loop
OVP
17
FBPFC
18
VEA
19
IAC
20
Input AC Current
©System General Corp.
Version 1.2(IAO33.0022.B2)
-3-
www.sg.com.tw
Nov.17, 2006
Product Specification
Green-mode PFC/Flyback-PWM Controller
SG6902
BLOCK DIAGRAM
©System General Corp.
Version 1.2(IAO33.0022.B2)
-4-
www.sg.com.tw
Nov.17, 2006
Product Specification
Green-mode PFC/Flyback-PWM Controller
SG6902
ABSOLUTE MAXIMUM RATINGS
Symbol
V
DD
I
AC
V
HIGH
V
LOW
P
D
T
J
T
STG
R
θ
j-C
T
L
ESD
Parameter
DC Supply Voltage*
Input AC Current
OPWM, OPFC, IAC
Others
Power Dissipation At T
A
< 50°C
Operating Junction Temperature
Storage Temperature Range
Thermal resistance (Junction to Case)
Lead Temperature (Wave soldering or IR, 10seconds)
ESD capability, HBM model
ESD capability, Machine model
Value
25
2
-0.3 to +25V
-0.3 to +7V
SOP
SSOP
-40 to +125
-55 to +150
SOP
SSOP
260
4.5
250
23.64
39.6
1.15
0.8
Unit
V
mA
V
V
W
℃
℃
℃/W
℃
KV
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 CONDITIONS
Symbol
T
A
Parameter
Operating Ambient Temperature*
Value
-30 to +85
Unit
℃
*For proper operation
ELECTRICAL CHARACTERISTICS (V
DD
=15V,T
A
=25°C UNLESS NOTED)
VDD Section
Symbol
V
DD-OP
I
DD-ST
I
DD-OP
V
TH-ON
V
DD-MIN
V
DD-OVP
T
VDD-OVP
V
DD-TH-G
Parameter
Continuously Operating Voltage
Start-up Current
Operating Current
Start Threshold Voltage
Minimum Operating Voltage
VDD OVP Threshold
Debounce Time of VDD OVP
VDD Low-Threshold Voltage to Exit
Green-OFF Mode
Test Conditions
V
TH-ON
–0.16V
OPFC, OPWM Open, RI =
24kΩ
Min.
Typ.
10
6
Max.
20
25
10
17
11
25.5
25
V
DD-MIN
+2.1
Unit
V
uA
mA
V
V
V
uS
V
15
9
23.5
RI = 24kΩ
8
V
DD-MIN
+0.9
16
10
24.5
V
DD-MIN
+1.5
©System General Corp.
Version 1.2(IAO33.0022.B2)
-5-
www.sg.com.tw
Nov.17, 2006
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