Product Specification
Low-cost Green-Mode PWM Controller for Flyback Converters
SG6848x1
System General Corp.
- 1 -
www.sg.com.tw
Version 1.3(IAO33.0002.B4)
Jan. 27, 2006
FEATURES
Green-mode PWM Controller
Low Start-up Current (5uA)
Low Operating Current (3mA)
Programmable PWM Frequency
Peak-current-mode Operation
Leading-edge Blanking
Built-in Synchronized Slope Compensation
Cycle-by-cycle Current Limiting
Constant Output Power Limit
Gate Output Voltage Clamped at 15V
Small SOT-26 Package Available
APPLICATIONS
General-purpose switching mode power supplies and
flyback power converters, such as
Battery chargers
Power adapters
Open-frame SMPS
Replacements for linear transformers and RCC
5V standby power for PC power supply.
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
continuously decrease PWM 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
3mA. As a result, 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). Cycle-by-cycle current limiting ensures safe
operation during short-circuits.
To protect the external power MOSFET from being
damaged by supply over voltage, the SG6848x1's output
driver is clamped at 15V. The SG6848x1's controllers can
be used to improve the performance and reduce the
production cost of power supplies. The SG6848x1 is the
best choice for replacing linear and RCC power supplies.
It is available in DIP-8 and SOT-26 packages.
TYPICAL APPLICATION
Product Specification
Low-cost Green-Mode PWM Controller for Flyback Converters
SG6848x1
System General Corp.
- 2 -
www.sg.com.tw
Version 1.3(IAO33.0002.B4)
Jan. 27, 2006
MARKING DIAGRAMS
PIN CONFIGURATION
ORDERING INFORMATION
Part Number
Package
SG6848T1 SOT-26
SG6848D1 DIP-8
SG6848TZ1
SOT-26 (Lead Free)
SG6848DZ1
DIP-8 (Lead Free)
PIN DESCRIPTIONS
Pin No.
Name
DIP-8 / (SOT-26)
Type Function
GATE
1 / (6)
Driver Output The totem-pole output driver for driving the power MOSFET.
VDD
2 / (5)
Supply
Power supply.
NC 3
No
connection.
SENSE
4 / (4)
Analog Input
Current sense. This pin senses the voltage across a resistor for peak-current-mode
control. If the voltage reaches the internal threshold, PWM output is disabled. This
activates cycle-by-cycle current limiting.
RI
5 / (3)
Analog
Input/Output
A resistor connected from the RI pin to GND pin will generate a constant current source
for the controller. This current is used to determine PWM frequency. Increasing the
resistance will reduce PWM frequency. A 95k resistor results in a 70kHz PWM
frequency.
NC 6
No
connection.
FB
7 / (2)
Analog Input
Feedback. The FB pin accepts the output voltage regulation signal. It provides feedback
to the internal PWM comparator to adjust the duty cycle.
GND
8 / (1)
Supply
Ground.
1
2
3
4
5
6
SOT-26
GND
FB
RI
GATE
VDD
SENSE
DIP-8
RI
NC
FB
GND
SENSE
NC
VDD
GATE
4
3
2
1
5
6
7
8
XXX:
AAH =SG6848T1
XXX:
AAH =SG6848TZ1
M
: Mask Version
W
: Week code A~Z=W1~W26
A~Z=W27~W52
:Lead free package
D
: D = DIP
P :
Z = Lead Free
Null = Regular Package
M: Mask Version
XXXXXX
: Wafer Lot
YY
: Year;
WW
: Week
V
: Assembly Location
8
1
SG6848DP1
MXXXXXXYYWWV
1
XXXMW
Product Specification
Low-cost Green-Mode PWM Controller for Flyback Converters
SG6848x1
System General Corp.
- 3 -
www.sg.com.tw
Version 1.3(IAO33.0002.B4)
Jan. 27, 2006
BLOCK DIAGRAM
Product Specification
Low-cost Green-Mode PWM Controller for Flyback Converters
SG6848x1
System General Corp.
- 4 -
www.sg.com.tw
Version 1.3(IAO33.0002.B4)
Jan. 27, 2006
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter
Value
Unit
V
DD
DC Supply Voltage
25
V
V
FB
Input Voltage to FB Pin
-0.3 to 6 V
V
V
SENSE
Input Voltage to Sense Pin
-0.3 to 6V
V
P
D
Power
Dissipation
300
mW
SOT-26 208.4
C/W
R
JA
Thermal Resistance (Junction to Air)
DIP-8 82.5
C/W
T
J
Operating Junction Temperature
-40 to +125
C
T
STG
Storage Temperature Range
-55 to +150
C
Pb free
260(+5/-0)
T
R
Peak
Reflow
Temperature
Pb 230(+5/-0)
C
* 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: -30C ~ 105C*
*For proper operation
ELECTRICAL CHARACTERISTICS (V
DD
=15V, T
A
= 25
C, unless noted)
VDD Section
Symbol Parameter
Test
Condition Min. Typ. Max.
Unit
V
OP
Continuously Operating Voltage
20
V
V
TH(ON)
Start-up
Threshold
Voltage
15.3 16.3 17.3 V
V
DD(MIN)
Min. Operating Voltage
10.9
11.7
12.5
V
I
DD ST
Start-up
Current
5
30
uA
I
DD OP
Operating Supply Current
GATE = 1nF
3
5
mA
V
DD-OVP
Over Voltage Protection
22
23.5
25
V
Feedback Input Section
Symbol Parameter
Test
Condition Min. Typ. Max.
Unit
Z
FB
Input
Impedance
2 k
I
OZ
Zero-duty-cycle Input Current
1.3
2.0
mA
V
OP
Open Loop Voltage
4.5
V
Oscillator Section
Symbol Parameter
Test
Condition Min. Typ. Max.
Unit
F
OSC
PWM Frequency
RI = 95k
65 70 75 kHz
F
OSC-GREEN
Green-mode Min. Frequency
RI = 95k
15
kHz
F
DY
Frequency Variation versus V
DD
Deviation
V
DD
= 14 to 20V
2
%
F
DT
Frequency Variation versus Temp. Deviation
T
A
= -30 to 105
2
%
I
N
Green-mode Start Threshold FB Input Current
1
mA
I
G
Green-mode Min. Freq. FB Input Current
1.16
mA
S
G
Green-mode Modulation Slope
RI = 95k
300
Hz/uA
R
I
RI pin resistance
66.5
150
k
Product Specification
Low-cost Green-Mode PWM Controller for Flyback Converters
SG6848x1
System General Corp.
- 5 -
www.sg.com.tw
Version 1.3(IAO33.0002.B4)
Jan. 27, 2006
Current Sense Section
Symbol Parameter
Test
Condition Min. Typ. Max.
Unit
Z
CS
Input
Impedance
10
k
T
PD
Delay
to
Output
100
nsec
V
TH,FLT
Current Limit Flatten Threshold Voltage
0.96
V
V
TH,VALLEY
Current Limit Valley Threshold Voltage
0.81
V
DC
SAW
Duty Cycle of SAW Limit
45
%
Gate Section
Symbol Parameter
Test
Condition Min. Typ. Max.
Unit
DC
(MAX)
Maximum
Duty
Cycle
70 75 80 %
DC
(MIN)
Minimum Duty Cycle
0
%
B
NK
Leading-edge Blanking Time
200
nsec
V
OL
Output Voltage Low
Sink current = 20mA
1.5
V
V
OH
Output Voltage High
Source current = 20mA 8
V
T
R
Rising Time
GATE = 1nF
250
nsec
T
F
Falling Time
GATE = 1nF
80
nsec
V
CLAMP
Output
Clamp
Voltage
V
DD
= 20V
15
17
V
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