Product Specification
Highly Integrated Green-Mode PWM Controller
SG6840
FEATURES
Green-Mode PWM
Supports the “Blue Angel” Norm
Low Start-up Current (30uA)
Low Operating Current (3mA)
Leading-Edge Blanking
Built-in Synchronized Slope Compensation
Totem Pole Output with Soft Driving
Improved EMI
Constant Output Power Limit
Current Mode Operation
Cycle-by-cycle Current Limiting
Under Voltage Lockout (UVLO)
Programmable PWM Frequency
GATE Output Maximum Voltage Clamped at 18V
Short Circuit Protection
Programmable Over Temperature Protection (OTP)
Few External Components Required
Low Cost
DESCRIPTION
This highly integrated PWM controller is
enhanced to provide low standby-power and stronger
protection features. In standby mode, the PWM
frequency is linearly reduced to cut power consumption,
and to provide a stable output voltage. The BiCMOS
fabrication process enables reducing the start-up
current to 30uA and the operating current to 3mA. This
results in increased power conversion efficiency.
During normal operation, the SG6840 acts as a fixed
frequency PWM controller with a programmable PWM
frequency. The PWM frequency can be controlled by
changing an external resistor.
The patented green-mode function reduces the
PWM frequency in response to decreases in the output
load. This function dramatically cuts power losses
under zero-load and light-load conditions, which helps
the power supply meet even the most stringent
international
power
conservation
regulations.
Proprietary synchronized slope compensation ensures
the stability of the current loop under continuous-mode
operation.
Built-in line-voltage compensation maintains a
constant output power limit over a wide range of AC
input voltages. An NTC thermistor is applied to sense
the ambient temperature to provide over temperature
protection. The SG6840 is available in 8-pin DIP and
SO packages.
APPLICATIONS
General-Purpose Switch Mode Power Supplies
Flyback Power Converters
Power Adapters
Open-Frame SMPS
Battery Charger Adapters
TYPICAL APPLICATION
From bridge rectifier
127~ 373VDC
RIN
VIN
RT
RA
RI
RT
RI
FB
VDD
GATE
C
IN
D1
From auxiliary
winding
Rg
Q1
SG6842
SENSE
R
S
GND
©System General Corp.
Version 1.7(IRO33.0003.B1)
-1-
www.sg.com.tw
AUG.11,2003
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6840
MARKING DIAGRAMS
8
T:
D = DIP, S = SOP
XXXXXXX:
Wafer Lot
SG6840T
XXXXXXXYYW
PIN CONFIGURATION
GND
FB
V IN
Ri
1
2
3
4
8
7
6
5
G a te
VDD
S ense
RT
YY:
Year;
WW:
Week
V:
Assembly Location
1
ORDERING INFORMATION
Part Number
SG6840S
SG6840D
Package
8-Pin SOP
8-Pin DIP
PIN DESCRIPTIONS
Pin No.
1
2
Symbol
GND
FB
Function
Ground
Feedback
Description
Ground.
Feedback. The FB pin provides the information used to regulate the power supply.
The PWM duty cycle is controlled by the FB pin.
The start-up current input. A start-up resistor is connected from the line-input to this
pin. For an off-line converter, a typical resistance would be 1.5M. The start-up resistor
can be adjusted to vary the line voltage compensation. The line voltage compensation
is used to maintain a constant output power limit.
Reference setting. The typical voltage is 1.3V. To generate a constant current for the
3
VIN
Start-up Current
Input
4
Ri
Reference Setting
SG6840, connecting a resistor to ground is suggested. Increasing the resistance will
decrease the current and reduce the switching frequency. Typically, Ri = 26KΩ.
Over temperature protection. A constant current is sourced out. An NTC thermistor is
connected from this pin to ground to sense the temperature. When the voltage of this
pin goes below the limit, over temperature protection will be enabled.
Current sense. This pin senses the voltage across a sense resistor. When the voltage
reaches the internal threshold, PWM output is disabled. In this manner, the controller
provides over current protection.
Power supply.
The totem-pole output driver for driving the power MOSFET.
5
RT
Temperature
Protection
6
7
8
SENSE
VDD
GATE
Current Sense
Power Supply
Driver Output
©System General Corp.
Version 1.7(IRO33.0003.B1)
-2-
www.sg.com.tw
AUG.11,2003
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6840
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
6
SENSE
6V
RT
2
5
+
_
Comp
FB
0.65V
1
GND
©System General Corp.
Version 1.7(IRO33.0003.B1)
-3-
www.sg.com.tw
AUG.11,2003
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6840
ABSOLUTE MAXIMUM RATINGS
Symbol
V
DD
I
out
V
FB
V
Sense
V
RT
V
RI
P
d
RΘ
j-a
T
J
T
A
T
stg
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
Junction Operating Temperature
Ambient Operating 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
-25 to 85
-55 to +150
3.0
300
Unit
V
V
mA
mA
V
V
V
V
W
℃/W
℃
℃
℃
kV
V
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
℃
kΩ
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
Zero Duty-Cycle Input Voltage
Test Condition
Min.
1/4.5
3
Typ.
1/5
4.5
Max.
1/5.5
6
2
1.2
Unit
V/V
KΩ
mA
V
©System General Corp.
Version 1.7(IRO33.0003.B1)
-4-
www.sg.com.tw
AUG.11,2003
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6840
Current Sense Section
Symbol
Zcs
T
PD
V
th
∆V
TH
@ I
IN
V
SENSE0
Parameter
Input Impedance
Delay to Output
Threshold Voltage for Current Limiting
Threshold Voltage Change versus the Input
Current of V
IN
Threshold voltage for I
VIN
= 80uA
Test Condition
Min.
8
Typ.
12
150
0.85
-0.15
0.81
Max.
16
200
0.9
-0.21
0.89
Unit
KΩ
nsec
V
V
V
I
VIN
= 0 uA
I
VIN
= 220 uA
I
VIN
= 80 uA
0.8
-0.09
0.73
Oscillator Section
Symbol
F
OSC
F
OSC-GREEN
V
G
V
N
S
G
F
DV
F
DT
Parameter
Frequency
Green-Mode Frequency
Green-Mode Voltage (V
G
= V
FB
- V
D
)
Normal-Mode Voltage (V
N
= V
FB
- V
D
)
(V
N
= 4 V for a Maximum Duty Cycle)
Slope for Green-Mode Modulation
Frequency Variation versus V
DD
Deviation
Frequency Variation versus Temp. Deviation
Test Condition
R
I
=26KΩ
R
I
=26KΩ
Min.
60
Typ.
65
10
1.3
Max.
70
15
Unit
KHz
KHz
V
1.7
R
I
=26KΩ
V
DD
=10 to 20V
T
A
=-25 to 85
℃
50
2
80
2.3
120
5
5
V
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
t
r
t
f
Parameter
Output Voltage Low
Output Voltage High
Rising Time
Falling Time
Test Condition
V
DD
= 12V, I
o
= 150mA
V
DD
= 12V, I
o
= 50mA
V
DD
=13V, C
L
=1nF
V
DD
=13V, C
L
=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
Minimum Operating Voltage
Test Condition
Min.
15
9
Typ.
16
10
Max.
17
11
Unit
V
V
©System General Corp.
Version 1.7(IRO33.0003.B1)
-5-
www.sg.com.tw
AUG.11,2003
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