Product Specification
High-integrated Green-mode PWM Controller
SG6841
FEATURES
Green-mode PWM to support “Blue Angel” Norm
Low start up current 30uA
Low operation current 3mA
Leading-edge blanking
Built-in synchronized slope compensation
Constant output power limit for universal AC input
Current mode operation
Cycle-by-cycle current limiting
Under voltage lockout (UVLO)
Programmable PWM frequency
GATE output maximum voltage clamped at 18V
Totem pole output includes soft driving for better
EMI
Build-in limited-power-control to meet safety
requirement
Programmable over-temperature protection
Few external components & low cost solution
DESCRIPTION
This highly integrated PWM controllers, SG6841 series,
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
conditions. This green-mode function assists the power
supply to easily meet the power conservation
requirement. Due to BiCMOS process, the start-up
current and operation current is reduced to 30uA and
3mA, respectively, to improve power conversion
efficiency. Large start-up resistance can be used for
further power saving. Built-in synchronized slope
compensation ensures the stability of peak current mode
control. A proprietary internal compensation ensures
constant output power limit for universal AC input
voltage from 90VAC to 264VAC.
SG6841 provides many protection functions.
Pulse by pulse current limit ensures a constant output
current under short circuit. If a short circuit failure or
over load happens, the SG6841 will shut off after a
continuous high voltage detection on FB pin. The gate
output is clamped at 18V to protect the power MOS
from over voltage damage.
An external NTC
thermistor can be applied to sense the ambient
temperature for over-temperature protection. The
SG6841 series are available in 8-pin DIP and SO
packages.
APPLICATIONS
General-purpose switching mode power supplies
and flyback power converters, and
Power Adapter
Open-frame SMPS
Battery Charger Adapter
TYPICAL APPLICATION
From bridge rectifier
127~ 373VDC
RIN
VIN
RT
RA
RI
SG6842
SENSE
R
S
FB
GND
VDD
GATE
C
IN
D1
From auxiliary
winding
Rg
Q1
RT
RI
©System General Corp.
Version 1.7 (IRO33.0001.B1)
-1-
www.sg.com.tw
JUL.25,2003
Product Specification
High-integrated Green-mode PWM Controller
SG6841
MARKING DIAGRAMS
8
PIN CONFIGURATION
T:
D = DIP, S = SOP
XXXXXXX:
Wafer Lot
YY:
Year;
WW:
Week
V:
Assembly Location
GND
FB
V IN
Ri
1
2
3
4
8
7
6
5
G a te
VDD
S ense
RT
SG6841T
XXXXXXXYYWWV
1
ORDERING INFORMATION
Part Number
SG6841S
SG6841D
Package
8-Pin SOP
8-Pin DIP
PIN DESCRIPTIONS
Pin No.
1
2
Symbol Function
GND
FB
Ground
Feedback
Description
Ground.
The signal from external compensation circuit is feed into this pin. The PWM duty cycle is
determined by this FB pin and current sense signal from Pin 6.
This pin is pulled high to the rectified line input through a resistor for start-up. Since the
start-up current requirement for SG6841 is very small, a large start-up resistance can be
used to minimize power loss. Under normal operation, this pin is also used to detect line
voltage to compensate for constant output power limit for universal AC input.
A resistor from RI pin to ground will generate a constant current source forSG6841. This
current is used to charge an internal capacitor and hence the switching frequency are
3
VIN
Start-Up
Input
4
Ri
Reference Setting
determined. Increasing the resistance will decrease the current source and reduce the
switching frequency. A 26kΩ resistor R
i
creates a 50uA constant current I
i
and generates
65kHz switching frequency.
For over-temperature protection. An external NTC thermistor is connected from this pin
to ground. The impedance of the NTC will decrease under high temperature. Once the
voltage on RT pin drops below a fixed limit, the PWM output will be disabled.
Current sense. The sensed voltage is used for current mode control and pulse-by-pulse
current limiting. If a short circuit failure happens on current sense resistor, the SG6841
will shut off after a continuous low voltage detection on SENSE pin.
Power Supply.
The totem-pole output driver for the power MOSFET. A soft driving waveform is
implemented to improve EMI.
5
RT
Temperature
Protection
6
7
8
SENSE
VDD
GATE
Current Sense
Power supply
Driver Output
©System General Corp.
Version 1.7 (IRO33.0001.B1)
-2-
www.sg.com.tw
JUL.25,2003
Product Specification
High-integrated Green-mode PWM Controller
SG6841
BLOCK DIAGRAM
RI
4
VDD
0.85V
VIN
3
+
_
ON/OFF
Driver
8
GATE
Internal
BIAS
Q
S
R
OSC
Green Mode
Controller
VDD
7
+
_
UVLO
16V/10V
Comp
Slope
Compensation
I
RT
2R
+
_
6
SENSE
6V
RT
5
Limited Power
Controller
4.2V
1
2
Comp
R
FB
0.65V
GND
©System General Corp.
Version 1.7 (IRO33.0001.B1)
-3-
www.sg.com.tw
JUL.25,2003
Product Specification
High-integrated Green-mode PWM Controller
SG6841
ABSOLUTE MAXIMUM RATINGS
Symbol
V
DD
Parameter
DC Supply Voltage
Zener clamp
Zener current
Gate Output Current
Input Voltage to FB Pin
Input Voltage to SENSE Pin
Input Voltage to RT Pin
Input Voltage to Ri Pin
Power Dissipation
Thermal Resistance Junction-air
DIP
SOP
Operating Junction Temperature
Operating Ambient Temperature
Storage Temperature Range
ESD Capability, HBM model
ESD Capability, Machine model
Value
30
32
10
500
-0.3 to 7V
-0.3 to 7V
-0.3 to 7V
-0.3 to 7V
1
82.5
141
150
-30 to 85
-55 to +150
3.0
250
Unit
V
V
mA
mA
V
V
V
V
W
℃/W
℃
℃
℃
kV
V
I
OUT
V
FB
V
Sense
V
RT
V
RI
P
D
RΘ
j-a
T
J
T
A
Tstg
RECOMMENDED OPERATING CONDITIONS
Symbol
V
DD
T
A
R
I
Parameter
DC Supply Voltage
Operating Ambient Temperature
Current source Setting
Value
<20
-20 to +85
26
Unit
V
℃
kohms
ELECTRICAL CHARACTERISTICS
Feedback Input Section
Symbol
A
V
Z
FB
I
FB
V
OZ
Parameter
Input-voltage to current-sense attenuation
Input impedance
Bias current
Input voltage for zero duty cycle
Test Condition
Min.
1/3.25
2
Typ.
1/3
4.5
Max.
1/2.75
8
2
1.2
Unit
V/V
kΩ
mA
V
©System General Corp.
Version 1.7 (IRO33.0001.B1)
-4-
www.sg.com.tw
JUL.25,2003
Product Specification
High-integrated Green-mode PWM Controller
SG6841
Current Sense Section
Symbol
Z
CS
T
PD
V
TH
Parameter
Input impedance
Delay to Output
Threshold voltage for current limit
Test Condition
Min.
8
Typ.
12
150
0.85
Max.
16
200
0.9
Unit
KΩ
nsec
V
I
VIN
= 0 uA
0.8
∆V
TH
@ I
VIN
The change of threshold voltage versus the input
current of the Vin
I
VIN
= 220 uA
-0.09
-0.15
-0.21
V
V
SENSE0
Tdelay-lps
Threshold voltage for I
VIN
= 80uA
The delay time of limited-power-control
I
VIN
= 80 uA
R
I
=26KOhms
0.73
0.81
31
0.89
V
msec
Oscillator Section
Symbol
F
OSC
Fosc-green
V
G
V
N
S
G
F
DV
F
DT
Parameter
Frequency in nominal mode
Frequency in green mode
End of green mode voltage at FB pin
Beginning of frequency reducing at FB pin
Slope for green mode modulation
Frequency variation versus V
DD
deviation
Frequency variation versus Temp. deviation
Test Condition
R
I
=26KOhms
R
I
=26KOhms
Min.
60
Typ.
65
10
1.9
2.6
Max.
70
16
Unit
KHz
KHz
V
V
R
I
=26KOhms
V
DD
=10 to 20V
T
A
=-30 to 85
℃
50
80
120
5
5
Hz/mV
%
%
PWM Section
Symbol
DC
(MAX)
DC
(MIN)
Bnk
Parameter
Maximum Duty Cycle
Minimum Duty Cycle
Leading edge blanking time
Test Condition
Min.
75
-
200
Typ.
80
-
270
Max.
90
0
350
Unit
%
%
nsec
Output Section
Symbol
V
OL
V
OH
tr
tf
Parameter
Output Voltage Low
Output Voltage High
Rising Time
Falling Time
Test Condition
V
DD
= 12V, Io = 150mA
V
DD
= 12V, Io = 50mA
V
DD
=13V, CL=1nF
V
DD
=13V, CL=1nF
Min.
8V
150
30
Typ.
Max.
1.5
Unit
V
V
nsec
nsec
250
50
350
90
Under-voltage Lockout Section
Symbol
V
TH(ON)
V
DD(min)
Parameter
Start Threshold Voltage
Min. Operating Voltage
Test Condition
Min.
15
9
Typ.
16
10
Max.
17
11
Unit
V
V
©System General Corp.
Version 1.7 (IRO33.0001.B1)
-5-
www.sg.com.tw
JUL.25,2003
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