Product Specification
Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback
SG6849
FEATURES
Linearly Decreasing PWM Frequency
Green-Mode under Light-Load and Zero-Load
Conditions
Constant Voltage (CV) and Constant Current (CC)
No Secondary Feedback
Low Startup Current (5uA)
Low Operating Current (3.6mA)
Leading-Edge Blanking
Constant Power Limit
Universal AC Input Range
Synchronized Slope Compensation
150°C OTP Sensor with Hysteresis
V
DD
Over Voltage Clamping
Cycle-by-Cycle Current Limiting
Under Voltage Lockout (UVLO)
Fixed PWM Frequency (65kHz/100kHz)
Gate Output Maximum Voltage Clamped at 16.7V
Small SOT-26 Package
DESCRIPTION
This highly integrated PWM controller provides several
features to enhance the performance of low power flyback
converters. To minimize standby power consumption, the
proprietary green-mode function provides off-time
modulation to linearly decrease the switching frequency
under light-load and zero-load conditions. This
green-mode function enables the power supply to easily
meet international power conservation requirements. The
supply voltage V
DD
is also used for feedback
compensation, to regulate the output voltage without
requiring a conventional TL431 and a photo-coupler.
Another advantage of the SG6849 is that the typical
startup current is only 5uA, while the typical operating
current can be as low as 3.6mA. A large startup resistance
could be used to achieve even higher power conversion
efficiency. Built-in synchronized slope compensation
maintains the stability of peak current-mode control.
Proprietary internal compensation ensures constant output
power limiting over a universal range of AC input
voltages, from 90VAC to 264VAC.The SG6849 provides
many protection functions. Pulse-by-pulse current
limiting ensures a constant output current, even if a short
circuit occurs. Also, the internal protection circuit will
disable PWM output, if V
DD
exceeds 22.7V. The gate
output is clamped at 16.7V to protect the power MOS
from over-voltage damage. The built-in over temperature
protection (OTP) function will shutdown the controller at
150°C with a 20°C hysteresis. The SG6849 is designed to
provide a low-cost total solution for flyback converters. It
is available in a small footprint, 6-pin, SOT-26 package.
APPLICATIONS
Low-power flyback power converters, such as
Battery chargers for cellular phones, cordless phones,
PDAs, digital cameras, and power tools.
Power adapters for ink jet printers, video game
consoles, and portable audio players.
Open-frame SMPS for TV/DVD standby and other
auxiliary supplies, home appliances, consumer
electronics, and PC 5V standby-power.
Replacements for linear transformers and RCC
SMPS.
TYPICAL IC APPLICATION
V
IN
R
IN
D
1
VDD
G ATE
D
O
C
O
W
AU X
V
O
Q1
C
IN
SE NSE
GN D
R
S
© System General Corp.
Version 1.2(IRO33.0026.B1)
-1-
www.sg.com.tw
Apr.06, 2004
Product Specification
Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback
SG6849
MARKING INFORMATION
M:
Mask Version
X:
B= SG6849-65T C= SG6849-100T
MXYWW
E= SG6849-65T (Lead free)
F= SG6849-100T (Lead free)
1
8
ZZZ:
65 or 100
Y:
Year
WW:
Work Week
PIN CONFIGURATION
SOT-26
GND
FB
NC
1
2
3
6
5
4
GATE
VDD
SENSE
DIP-8
GATE
VDD
NC
SENSE
1
2
3
4
8
7
6
5
GND
FB
NC
NC
SG6849-ZZZDP
XXXXXXXYYWWV
D:
D=DIP
P :
Z =Lead free
Null=Regular package
XXXXXXX:
Wafer Lot
YY:
Year
WW:
Week
1
ORDERING INFORMATION
Part Number
SG6849-65T
SG6849-100T
SG6849-65D
SG6849-100D
SG6849-65TZ
SG6849-100TZ
SG6849-65DZ
SG6849-100DZ
PWM Frequency
65kHz
100kHz
65kHz
100kHz
65kHz
100kHz
65kHz
100kHz
Package
6-Pin SOT-26
6-Pin SOT-26
8-pin DIP-8
8-pin DIP-8
6-Pin SOT-26 (Lead Free)
6-Pin SOT-26 (Lead Free)
8-pin DIP-8 (Lead Free)
8-pin DIP-8 (Lead Free)
PIN DESCRIPTIONS
Name
GATE
VDD
NC
SENSE
NC
NC
FB
GND
Pin No.
Type
DIP-8 SOT-26
1
2
3
4
5
6
7
8
6
5
NA
4
3
NA
2
1
Supply
Function
Power supply.
NC pin.
Current sense. It senses the voltage across a sensed resistor. To provide over-current
Driver Output The totem-pole output driver to drive the power MOSFET.
Analog Input protection, PWM output is disabled if the voltage exceeds an internal threshold. This pin
also provides current information for current-mode control.
NC pin.
NC pin.
Feedback. The FB pin provides feedback information to the internal PWM comparator.
Analog Input This feedback is used to control the duty cycle. When no feedback is provided, this pin is
left open.
Supply
Ground.
© System General Corp.
Version 1.2(IRO33.0026.B1)
-2-
www.sg.com.tw
Apr.06, 2004
Product Specification
Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback
SG6849
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter
DC Supply Voltage*
V
DD
V
FB
V
SENSE
P
D
R
θ
JA
R
θ
JC
T
J
T
STG
T
L
Zener Clamp
Zener Current
FB Pin Input Voltage
Sense Pin Input Voltage
Power Dissipation
Thermal Resistance (Junction to Air)
Thermal Resistance (Junction to Case)
Operating Junction Temperature
Storage Temperature Range
Lead Temperature (Soldering)
ESD Capability, Human Body Model
ESD Capability, Machine Model
*All voltage values, except differential voltages, are given with respect to the network ground terminal.
20 sec
10 sec
SOT-26
DIP-8
SOT-26
DIP-8
SOT-26
DIP-8
Value
25
30
10
-0.3 to 7
-0.3 to 7
300
243.3
113.0
115
67.1
150
-55 to +150
220
260
3.0
300
Unit
V
V
mA
V
V
mW
°C/W
°C/W
°C
°C
°C
kV
V
OPERATING CONDITIONS
Symbol
V
DD
T
A
Parameter
DC Supply Voltage
Operating Ambient Temperature
Value
<22.7
-30 to +85
Unit
V
°C
ELECTRICAL CHARACTERISTICS
(V
DD
=15V, T
A
=25°C)
Feedback Input Section
Symbol
I
OZ
V
FB
R
FB
V
DDZ
Parameter
Zero Duty-Cycle FB Input Current
Open Loop Voltage
Input Impedance
V
DD
Feedback Threshold Voltage*
Test Condition
Min.
Typ.
1.15
4.5
Max.
1.4
Unit
mA
V
kΩ
FB Input Current = 0.1mA
FB Input Current = 0mA
FB Input Current = 0.8mA
20
18
2.4
22.7
20
25
22
V
V
*The feedback input is pulled by a transistor that is controlled by the V
DD
signal while V
DD
≧
V
DDZ
.
© System General Corp.
Version 1.2(IRO33.0026.B1)
-4-
www.sg.com.tw
Apr.06, 2004
Product Specification
Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback
SG6849
Current Sense Section
Symbol
T
PD
Parameter
Propagation Delay
Test Condition
VDD = 20V
Min.
0.84
0.72
0.58
0.76
0.65
0.52
Typ.
100
0.89
0.77
0.63
0.81
0.70
0.57
Max.
0.94
0.82
0.68
0.86
0.75
0.62
Unit
ns
V
V
V
V
V
V
Current Limiting Valley Threshold Voltage for 65kHz VDD = 15V
V
TH,VA
VDD = 10V
VDD = 20V
Current Limiting Valley Threshold Voltage for 100kHz VDD = 15V
VDD = 10V
T
ON
T
OFF
V
LIMIT
Ramp
V
TH,FT
0.77V
High-Line
Sense Voltage
Low-Line Sense
Voltage
V
TH,VA
0V
T
1
T
2
Oscillator Section
Symbol
F
OSC
F
OSC
F
OSC-G-BK
F
OSC-G-OFF
I
FB-G-OFF
F
DV
V
DD-TH-G
Parameter
SG6849–65 Frequency
SG6849–100 Frequency
Green-Mode Burst Back Frequency*
Green-Mode OFF Frequency*
Green-Mode OFF FB Input Current
Frequency Variation versus V
DD
Deviation
V
DD
-Low Threshold Voltage for Exiting
Green-Mode OFF
Test Condition Min.
60
92
20
0.9
V
DD
= 10 to 20V
V
DD OFF
+1.0
Typ.
65
100
25
0
1.15
Max.
70
108
30
1.4
2
Unit
kHz
kHz
kHz
kHz
mA
%
V
DD OFF
+1.5
V
DD OFF
+2.0 V
*Please see the “Green-Mode Burst Back (F
OSC-G-BK
) and Green-Mode OFF Frequency (F
OSC-G-OFF
) vs. V
DD
” curves.
© System General Corp.
Version 1.2(IRO33.0026.B1)
-5-
www.sg.com.tw
Apr.06, 2004
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