Product Specification
Low Cost Green-Mode PWM Controller for Flyback Converters
SG6848
FEATURES
Green-Mode PWM
Supports the “Blue Angel” Standard
Low Start-up Current (5uA)
Low Operating Current (2mA)
Leading-Edge Blanking
Constant Output Power Limit
Universal Input
Built-in Synchronized Slope Compensation
Current Mode Operation
Cycle-by-cycle Current Limiting
Under Voltage Lockout (UVLO)
Programmable PWM Frequency
Gate Output Voltage Clamped at 15V
Low Cost
Few External Components Required
Small SOT-26 Package
DESCRIPTION
This highly-integrated PWM controller provides
several special enhancements designed to meet the low
standby-power needs of low-power SMPS. 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 enables the power
supply to easily meet even the strictest power
conservation requirements.
The BiCMOS fabrication process enables reducing
the start-up current to 5uA, and the operating current to
2mA. To further improve power conservation, a large
start-up resistance can be used. Built-in synchronized
slope compensation ensures the stability of peak current
mode control. Proprietary internal compensation provides
a constant output power limit over a universal AC input
range (90VAC to 264VAC). Pulse-by-pulse current
limiting ensures safe operation even during short-circuits.
To protect the external power MOSFET from being
damaged by supply over voltage, the SG6848’s output
driver is clamped at 15V. SG6848 controllers can be used
to improve the performance and reduce the production
cost of power supplies. The SG6848 is the best choice for
replacing linear and RCC-mode power adapters. It is
available in 8-pin DIP and 6-pin SOT-26 packages.
APPLICATIONS
General-purpose switching mode power supplies and
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, and consumer
electronics
Replacements for linear transformers and RCC
SMPS
PC 5V standby power.
TYPICAL APPLICATION
From bridge rectifier
120~ 380VDC
From auxiliary winding
R
IN
1.5M
VDD
FB
C6
472p
OUTPUT
C
IN
10u
R7
100
SG6848
SENSE
R9
95k
RI
GND
R
S
4.7
© System General Corp.
Version 1.4(IRO33.0010.B2)
-1-
www.sg.com.tw
Apr.08, 2004
Product Specification
Low Cost Green-Mode PWM Controller for Flyback Converters
SG6848
PIN CONFIGURATION
SOT-26
MARKING DIAGRAMS
MXYWW
M:
Mask Version
X:
A=SG6848
D=SG6848 (Lead Free)
Y:
Year;
WW:
Work Week
GND
FB
RI
1
2
3
6
5
4
GATE
VDD
SENSE
1
8
D:
D=DIP
P :
Z =Lead Free
Null=Regular Package
XXXXXXX:
Wafer Lot
YY:
Year;
WW:
Week
V:
Assembly Location
DIP-8
GATE
VDD
NC
SENSE
1
2
3
4
8
7
6
5
GND
FB
NC
RI
XXXXXXXYYWWV
SG6848DP
1
ORDERING INFORMATION
Part Number
SG6848T
SG6848D
SG6848TZ
SG6848DZ
PWM Frequency
70kHz
70kHz
70kHz
70kHz
Package
6-Pin SOT-26
8-pin DIP-8
6-Pin SOT-26 (Lead Free)
8-pin DIP-8 (Lead Free)
PIN DESCRIPTIONS
Name
GATE
VDD
NC
SENSE
Pin No.
DIP-8 / (SOT-26)
Type
Driver Output
Supply
Function
The totem-pole output driver for driving the power MOSFET.
Power supply.
NC pin.
Current sense. This pin senses the voltage across a resistor. When the voltage reaches
1 / (6)
2 / (5)
3
4 / (4)
Analog Input
the internal threshold, PWM output is disabled. This activates over-current protection.
This pin also provides current amplitude information for current-mode control.
A resistor connected from the RI pin to ground will generate a constant current source for
the SG6848. This current is used to charge an internal capacitor, to determine the
switching frequency. Increasing the resistance will reduce the amplitude of the current
source and reduce the switching frequency. A 95kΩ resistor R
i
results in a 50uA constant
current I
i
and a 70kHz switching frequency.
NC pin.
RI
5 / (3)
Analog
Input/Output
NC
FB
GND
6
7 / (2)
8 / (1)
Analog Input
Supply
Feedback. The FB pin provides the output voltage regulation signal. It provides feedback
to the internal PWM comparator, so that the PWM comparator can control the duty cycle.
Ground.
© System General Corp.
Version 1.4(IRO33.0010.B2)
-2-
www.sg.com.tw
Apr.08, 2004
Product Specification
Low Cost Green-Mode PWM Controller for Flyback Converters
SG6848
BLOCK DIAGRAM
GND
8 (1)
RI
5 (3)
ON/OFF
Driver
Internal
Bias
V
DD
1 (6)
GATE
V
DD
2 (5)
OSC
S Q
R
OCP
Comp
Vlimit
ramp
Blanking
Circuit
4 (4)
SENSE
+
_
UVLO
16.3V/11.7V
Green
Mode
Controller
Slope
Compensation
PWM
Comp
4.8V
7 (2)
FB
© System General Corp.
Version 1.4(IRO33.0010.B2)
-3-
www.sg.com.tw
Apr.08, 2004
Product Specification
Low Cost Green-Mode PWM Controller for Flyback Converters
SG6848
ABSOLUTE MAXIMUM RATINGS
Symbol
V
DD
Parameter
DC Supply Voltage *
Zener Clamp
Zener Current
Value
25
26
10
-0.3 to 6 V
-0.3 to 6V
300
150
SOT-26
DIP-8
20 sec
10 sec
SOT-26
DIP-8
208.4
82.5
-55 to +150
220
260
3.0
300
Unit
V
V
mA
V
V
mW
℃
°C/W
°C/W
℃
°C
kV
V
V
FB
V
SENCE
P
D
T
J
R
θ
JA
T
STG
T
L
Input Voltage to FB Pin
Input Voltage to Sense Pin
Power Dissipation
Operating Junction Temperature
Thermal Resistance (Junction to Air)
Storage Temperature Range
Lead Temperature (Soldering)
ESD Capability, HBM Model
ESD Capability, Machine Model
* All voltage values, except differential voltages, are given with respect to the network ground terminal.
OPERATING CONDITIONS
Symbol
V
DD
T
A
Parameter
DC Supply Voltage
Operating Ambient Temperature
Value
≦20
-30 to +105
Unit
V
℃
ELECTRICAL CHARACTERISTICS (T
A
= 25°C, V
DD
=15V)
Feedback Input Section
Symbol
I
OZ
V
OP
Parameter
Zero Duty Cycle Input Current
Open Loop Voltage
Test Condition
Min.
Typ.
1.3
4.5
Max.
2.0
Unit
mA
V
Current Sense Section
Symbol
Z
CS
T
PD
V
TH,FLT
V
TH,VALLEY
Parameter
Input Impedance
Delay to Output
Current Limit Flatten Threshold Voltage
Current Limit Valley Threshold Voltage
Test Condition
Min.
10
Typ.
150
1.0
Max.
200
0.90
Unit
kΩ
nsec
V
V
0.80
0.85
© System General Corp.
Version 1.4(IRO33.0010.B2)
-4-
www.sg.com.tw
Apr.08, 2004
Product Specification
Low Cost Green-Mode PWM Controller for Flyback Converters
SG6848
Oscillator Section
Symbol
F
OSC
F
OSC-GREEN
I
G
I
N
S
G
F
DY
F
DT
Parameter
Frequency
Green-Mode Frequency
Green-Mode FB Input Current
Green-Mode Start Threshold FB Input Current
I
n
= 0.3mA for a Maximum Duty Cycle
Green-Mode Modulation Slope
Frequency Variation versus V
DD
Deviation
Frequency Variation versus Temp. Deviation
Test Condition
R
I
=95kΩ
R
I
=95kΩ
Min.
65
Typ.
70
13
1.16
1
Max.
75
15
Unit
kHz
kHz
mA
mA
Hz/uA
R
I
=95kΩ
V
DD
=12 to 20V
T
A
=-30 to 105
℃
300
0.02
2
2
%
%
PWM Section
Symbol
DC
(MAX)
DC
(MIN)
B
NK
Parameter
Maximum Duty Cycle
Minimum Duty Cycle
Leading-Edge Blanking Time
Test Condition
Min.
70
-
Typ.
75
1
250
Max.
80
2
Unit
%
%
nsec
Output Section
Symbol
V
OL
V
OH
T
R
T
F
V
CLAMP
Parameter
Output Voltage Low
Output Voltage High
Rising Time
Falling Time
Output Clamp Voltage
Test Condition
V
DD
=15V, I
o
=20mA
V
DD
=15V, I
o
=20mA
V
DD
=15V, C
L
=1nF
V
DD
=15V, C
L
=1nF
V
DD
=20V
Min.
8
Typ.
Max.
1.5
Unit
V
V
nsec
nsec
V
50
30
15
200
150
17
Under Voltage Lockout Section
Symbol
V
TH(ON)
V
DD(MIN)
Parameter
Start Threshold Voltage
Min. Operating Voltage
Test Condition
T
A
=25°C
T
A
=25°C
Min.
15.3
10.9
Typ.
16.3
11.7
Max.
17.3
12.5
Unit
V
V
Total Standby Current Section
Symbol
I
DD ST
I
DD OP
Parameter
Start-up Current
Operating Supply Current
Test Condition
V
DD
=15V
V
DD
=15V
Min.
Typ.
5
2
Max.
30
5
Unit
uA
mA
© System General Corp.
Version 1.4(IRO33.0010.B2)
-5-
www.sg.com.tw
Apr.08, 2004
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