Product Specification
Highly-Integrated Green-Mode PWM Controller
SG6846
the switching frequency under light-load conditions.
Under zero-load conditions, the power supply enters
burst-mode. This completely shuts off PWM output. The
output restarts just before the supply voltage drops below
the UVLO lower limit. This green-mode function enables
power supplies to easily meet international power
conservation requirements.
The SG6846 is especially designed for SMPS with
surge-current output. It is incorporated with a two-level
OCP function. Besides the cycle-by-cycle current limiting,
if the switching current is higher than 2/3 of the
peak-current threshold for a delay time, over-current
protection will be activated such that the SG6846 will be
totally shutdown. Other protection functions include: AC
input brownout protection with hysteresis, and VDD
over-voltage protection. For over-temperature protection,
an external NTC thermistor can be applied to sense the
ambient temperature. When OCP, VDD OVP, or OTP are
activated, an internal latch circuit is used to latch-off the
controller. The latch will reset when the VDD supply is
removed.
Other features of this controller include: Built-in
synchronized slope compensation, proprietary internal
compensation for constant output power limit over
universal AC input range. Also, the gate output is clamped
at 18V to protect the external MOSFET from over-voltage
damage.
The SG6846 series controllers are available in both
8-pin DIP and SO packages.
FEATURES
Two-level OCP with 96mS delay time
Peak-current-mode operation with cycle-by-cycle
current limiting
PWM frequency continuously decreasing w/ burst
mode at light loads
Low start-up current (8uA)
Low operating current (3.7mA)
VDD over-voltage protection (OVP)
AC input brownout protection with hysteresis
Programmable over-temperature protection (OTP)
Constant power limit over universal AC input range
Internal latch circuit for OTP, OVP, OCP
Very few external components
APPLICATIONS
General-purpose switch mode power supplies and
flyback power converters, including:
Power adapters
Open-frame SMPS
Specifically fit for SMPS with surge-current output,
such as for printers, scanners, motor drivers, etc.
DESCRIPTION
The highly integrated SG6846 series of PWM
controllers provides several features to enhance the
performance of flyback converters. To minimize standby
power consumption, a proprietary green-mode function
provides off-time modulation to continuously decrease
TYPICAL APPLICATION
© System General Corp.
Version 1.0(IAO33.0008.B0)
-1-
www.sg.com.tw
Sep. 30, 2004
Product Specification
Highly-Integrated Green-Mode PWM Controller
SG6846
PIN CONFIGURATION
MARKING DIAGRAMS
8
F:
L = OTP Latch
C = Hysteresis OTP
T:
D = DIP, S = SOP
SG6846FTP
MXXXXXXYYWWV
P:
Null = regular
Z = Lead free
M:
Mask version
XXXXXX:
Wafer Lot
YY:
Year;
WW:
Week
V:
Assembly Location
GND
FB
VIN
RI
1
2
3
4
8
7
6
5
GATE
VDD
SENSE
RT
1
ORDERING INFORMATION
Part Number
SG6846LS
SG6846LD
SG6846CS
SG6846CD
SG6846LSZ
SG6846LDZ
SG6846CSZ
SG6846CDZ
Package
8-Pin SOP
8-Pin DIP
8-Pin SOP
8-Pin DIP
8-Pin SOP (Lead Free)
8-Pin DIP (Lead Free)
8-Pin SOP (Lead Free)
8-Pin DIP (Lead Free)
OTP Mode
Latch off
Latch off
Hysteresis
Hysteresis
Latch off
Latch off
Hysteresis
Hysteresis
© System General Corp.
Version 1.0(IAO33.0008.B0)
-2-
www.sg.com.tw
Sep. 30, 2004
Product Specification
Highly-Integrated Green-Mode PWM Controller
SG6846
PIN DESCRIPTIONS
Pin No. Symbol
1
2
GND
FB
Function
Ground
Feedback
Line-voltage
Detection
Reference
Setting
Temperature
Detection
Description
Ground.
The signal from the external compensation circuit is fed into this pin. This FB pin and the
current-sense signal from Pin 6 determine the PWM duty cycle.
Line-voltage detection. The line-voltage detection is used for brownout protection with
hysteresis. Constant output power limit over universal AC input range is also achieved using
this VIN signal. It is suggested to add low pass filter to filter out line ripple on bulk capacitor.
A resistor from the RI pin to ground will generate a reference current source inside SG6846.
This determines the switching frequency. Increasing the resistance will reduce the switching
frequency. Using a 26kΩ resistor Ri results in a 65kHz switching frequency.
For over-temperature protection. An external NTC thermistor is connected from this pin to
GND pin. The impedance of the NTC will decrease at high temperatures. Once the voltage
of the RT pin drops below a threshold, PWM output will be disabled.
Current sense. The sensed voltage is used for peak-current-mode control and
cycle-by-cycle current limiting. If the switching current is higher than 2/3 of the peak-current
threshold for longer than 96ms, over-current protection will be activated. This two-level OCP
feature is especially suitable for SMPS with surge current output.
Power Supply. The internal protection circuit will disable PWM output when VDD over
voltage.
The totem-pole output driver for the power MOSFET. A soft driving waveform is
implemented for improved EMI.
3
VIN
4
RI
5
RT
6
SENSE
Current Sense
7
8
VDD
GATE
Power Supply
Driver Output
BLOCK DIAGRAM (OTP LATCH VERSION)
© System General Corp.
Version 1.0(IAO33.0008.B0)
-3-
www.sg.com.tw
Sep. 30, 2004
Product Specification
Highly-Integrated Green-Mode PWM Controller
SG6846
ABSOLUTE MAXIMUM RATINGS
Symbol
V
DD
V
L
P
D
R
Θ
J-C
T
J
T
STG
T
L
Parameter
Supply Voltage
Input Voltage to VIN, FB, SENSE, RT, RI Pin
Power Dissipation
Thermal Resistance
Operating Ambient Temperature
Storage Temperature Range
Lead Temperature (Soldering)
Test Condition
Value
25
-0.3 to 7V
Unit
V
V
mW
°C/W
°C
°C
°C
at T
A
< 50°C
Junction-Case
DIP
SOP
DIP
SOP
800
400
67.1
41.2
-40 to 125
-65 to +150
10 sec
10 sec
DIP
SOP
260
230
*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°C ~ 85°C*
*For proper operation
ELECTRICAL CHARACTERISTICS (VDD = 15V, T
A
= 27°C, unless noted)
VDD Section
Symbol
V
OP
V
TH-ON
V
TH-OFF
I
DD-ST
I
DD-OP
V
DD-OVP
T
VDD-OVP
I
DD-OVP
V
DD-TH-G
Parameter
Continuously Operating Voltage
On Threshold Voltage
Off Threshold Voltage
Start-Up Current
Operating Supply Current
VDD Over Voltage Protection (Latch off)
VDD OVP Debounce Time
VDD OVP Latch-up Holding Current
VDD Low-threshold Voltage to Exit Green-OFF
Mode
Test Condition
Min.
15.5
9.5
Typ.
16.5
10.5
8
3.7
Max.
20
17.5
11.5
30
5
24.6
Unit
V
V
V
uA
mA
V
usec
uA
V
VDD = 15V
GATE Open
22.6
RI = 26KΩ
VDD = 5V, T
A
= 27 C
o
23.6
100
45
V
TH(OFF)
+
1.25
VIN Section
Symbol
V
IN-OFF
V
IN-ON
Parameter
PWM Turn-off Threshold Voltage
PWM Turn-on Threshold Voltage
Test Condition
Min.
0.67
Typ.
0.72
V
IN-OFF
+
0.2
Max.
0.77
Unit
V
V
Feedback Input Section
Symbol
A
V
Z
FB
V
FB0
Parameter
Input-Voltage to Current-Sense Attenuation
Input Impedance
FB Pin open voltage
Test Condition
Min.
4
Typ.
1/4.2
5.5
6.2
Max.
7
Unit
V/V
KΩ
V
© System General Corp.
Version 1.0(IAO33.0008.B0)
-4-
www.sg.com.tw
Sep. 30, 2004
Product Specification
Highly-Integrated Green-Mode PWM Controller
SG6846
Current Sense Section
Symbol
Z
CS
T
PD
B
NK
V
TH-P
@V
IN
=1V
V
TH-P
@V
IN
=3V
V
TH-O
@V
IN
=1V
V
TH-O
@V
IN
=3V
T
DELAY-OCP
Parameter
Input Impedance
Delay to Output
Leading Edge Blanking Time
Threshold Voltage for Current Limit
Threshold Voltage for Current Limit
2/3 Threshold Voltage for Current Limit
2/3 Threshold Voltage for Current Limit
The Delay Time for Over-current Protection
Test Condition
Min.
Typ.
12
100
360
Max.
200
Unit
kΩ
nsec
nsec
V
V
V
V
msec
VIN = 1V, RI = 26kΩ
VIN =3V, RI = 26kΩ
VIN = 1V, RI = 26kΩ
VIN =3V, RI = 26kΩ
RI = 26KΩ
0.83
0.70
0.61
0.51
96
Oscillator Section
Symbol
F
OSC
F
OSC-GREEN
V
N
V
G
S
G
F
DV
F
DT
Parameter
PWM Frequency
Green-mode Frequency
FB Pin Threshold for the Beginning of Green
Mode
Green-OFF Mode Voltage at FB pin
Slope for Green-Mode Modulation
Frequency Variation Versus VDD Deviation
Frequency Variation Versus Temp. Deviation
Test Condition
RI = 26kΩ
RI = 26kΩ
Min.
60
20
Typ.
65
22.5
2.1
1.6
Max.
70
25
Unit
KHz
KHz
V
V
Hz/mV
RI = 26kΩ
VDD = 11.5V to 20V
T
A
= -30 to 85
℃
85
5
1.5
5
%
%
Frequenc
y
F
OSC
: 65kHz
PWM Frequency
S
G
: 85Hz/mV
F
OSC-GREEN
: 22.5kHz
F
OSC-GOFF
: 0kHz
V
G
: 1.6V
V
N
: 2.1V
V
F
B
© System General Corp.
Version 1.0(IAO33.0008.B0)
-5-
www.sg.com.tw
Sep. 30, 2004
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