ETC SG6846

Product Specification
SG6846
Highly-Integrated Green-Mode PWM Controller
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.
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
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.
TYPICAL APPLICATION
© System General Corp.
Version 1.0(IAO33.0008.B0)
-1-
www.sg.com.tw
Sep. 30, 2004
Product Specification
SG6846
Highly-Integrated Green-Mode PWM Controller
MARKING DIAGRAMS
PIN CONFIGURATION
F: L = OTP Latch
C = Hysteresis OTP
8
T: D = DIP, S = SOP
SG6846FTP
MXXXXXXYYWWV
1
GND
1
8
GATE
FB
2
7
VDD
M: Mask version
VIN
3
6
SENSE
XXXXXX: Wafer Lot
RI
4
5
RT
P: Null = regular
Z = Lead free
YY: Year; WW: Week
V: Assembly Location
ORDERING INFORMATION
Part Number
Package
OTP Mode
SG6846LS
8-Pin SOP
Latch off
SG6846LD
8-Pin DIP
Latch off
SG6846CS
8-Pin SOP
Hysteresis
SG6846CD
8-Pin DIP
Hysteresis
SG6846LSZ
8-Pin SOP (Lead Free)
Latch off
SG6846LDZ
8-Pin DIP (Lead Free)
Latch off
SG6846CSZ
8-Pin SOP (Lead Free)
Hysteresis
SG6846CDZ
8-Pin DIP (Lead Free)
Hysteresis
© System General Corp.
Version 1.0(IAO33.0008.B0)
-2-
www.sg.com.tw
Sep. 30, 2004
Product Specification
SG6846
Highly-Integrated Green-Mode PWM Controller
PIN DESCRIPTIONS
Pin No. Symbol
Function
Description
Ground.
1
GND
Ground
2
FB
Feedback
3
VIN
4
5
RI
RT
Line-voltage
Detection
Reference
Setting
Temperature
Detection
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
6
SENSE
Current Sense
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.
7
VDD
Power Supply
8
GATE
Driver 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.
BLOCK DIAGRAM (OTP LATCH VERSION)
© System General Corp.
Version 1.0(IAO33.0008.B0)
-3-
www.sg.com.tw
Sep. 30, 2004
Product Specification
SG6846
Highly-Integrated Green-Mode PWM Controller
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
VDD
Supply Voltage
25
V
VL
Input Voltage to VIN, FB, SENSE, RT, RI Pin
-0.3 to 7V
V
PD
Power Dissipation
RΘ J-C
Thermal Resistance
TJ
Operating Ambient Temperature
TSTG
Storage Temperature Range
TL
Lead Temperature (Soldering)
Test Condition
at T A < 50°C
Value
DIP
800
SOP
400
DIP
67.1
SOP
41.2
Junction-Case
Unit
mW
°C/W
-40 to 125
°C
-65 to +150
°C
10 sec
DIP
260
10 sec
SOP
230
°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: -30°C ~ 85°C*
*For proper operation
ELECTRICAL CHARACTERISTICS (VDD = 15V, T A = 27°C, unless noted)
VDD Section
Symbol
Parameter
VOP
Continuously Operating Voltage
VTH-ON
On Threshold Voltage
VTH-OFF
Off Threshold Voltage
IDD-ST
Start-Up Current
VDD = 15V
IDD-OP
Operating Supply Current
GATE Open
VDD-OVP
VDD Over Voltage Protection (Latch off)
TVDD-OVP
VDD OVP Debounce Time
IDD-OVP
VDD-TH-G
VDD OVP Latch-up Holding Current
Test Condition
Min.
Typ.
15.5
16.5
9.5
22.6
RI = 26KΩ
o
VDD = 5V, TA = 27 C
Max.
Unit
20
V
17.5
V
10.5
11.5
V
8
30
uA
3.7
5
mA
23.6
24.6
V
100
usec
45
uA
VDD Low-threshold Voltage to Exit Green-OFF
VTH(OFF) +
Mode
1.25
V
VIN Section
Symbol
Parameter
VIN-OFF
PWM Turn-off Threshold Voltage
VIN-ON
PWM Turn-on Threshold Voltage
Test Condition
Min.
Typ.
Max.
Unit
0.67
0.72
0.77
V
VIN-OFF +
V
0.2
Feedback Input Section
Symbol
Parameter
AV
Input-Voltage to Current-Sense Attenuation
ZFB
Input Impedance
VFB0
FB Pin open voltage
© System General Corp.
Version 1.0(IAO33.0008.B0)
Test Condition
Min.
Typ.
Max.
1/4.2
4
5.5
6.2
-4-
Unit
V/V
7
KΩ
V
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Sep. 30, 2004
Product Specification
SG6846
Highly-Integrated Green-Mode PWM Controller
Current Sense Section
Symbol
Parameter
ZCS
Input Impedance
Test Condition
Min.
Typ.
12
Max.
Unit
TPD
Delay to Output
100
BNK
Leading Edge Blanking Time
360
nsec
VTH-P @VIN=1V
Threshold Voltage for Current Limit
VIN = 1V, RI = 26kΩ
0.83
V
VTH-P @VIN=3V
Threshold Voltage for Current Limit
VIN =3V, RI = 26kΩ
0.70
V
VTH-O @VIN=1V
2/3 Threshold Voltage for Current Limit
VIN = 1V, RI = 26kΩ
0.61
V
VTH-O @VIN=3V
2/3 Threshold Voltage for Current Limit
VIN =3V, RI = 26kΩ
0.51
V
TDELAY-OCP
The Delay Time for Over-current Protection
RI = 26KΩ
96
msec
kΩ
200
nsec
Oscillator Section
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
FOSC
PWM Frequency
RI = 26kΩ
60
65
70
KHz
Green-mode Frequency
RI = 26kΩ
20
22.5
25
KHz
FOSC-GREEN
VN
FB Pin Threshold for the Beginning of Green
2.1
Mode
VG
Green-OFF Mode Voltage at FB pin
SG
Slope for Green-Mode Modulation
RI = 26kΩ
FDV
Frequency Variation Versus VDD Deviation
VDD = 11.5V to 20V
FDT
Frequency Variation Versus Temp. Deviation
TA = -30 to 85 ℃
V
1.6
V
85
Hz/mV
1.5
5
%
5
%
Frequenc
y
PWM Frequency
FOSC: 65kHz
SG: 85Hz/mV
FOSC-GREEN: 22.5kHz
FOSC-GOFF: 0kHz
VF
VG: 1.6V
VN: 2.1V
B
© System General Corp.
Version 1.0(IAO33.0008.B0)
-5-
www.sg.com.tw
Sep. 30, 2004
Product Specification
SG6846
Highly-Integrated Green-Mode PWM Controller
PWM Section
Symbol
Parameter
DMAX
Maximum Duty Cycle
Test Condition
Min.
Typ.
Max.
Unit
80
85
90
%
VOL
Output Voltage Low
VDD = 15V, Io = 50mA
VOH
Output Voltage High
VDD = 12V, Io = 50mA
1.5
V
TR
Rising Time
VDD = 15V, CL=1nF
350
nsec
TF
Falling Time
VDD = 15V, CL=1nF
50
nsec
VCLAMP
Gate Output Clamping Voltage
VDD = 20V
18
V
8V
V
Over Temperature Protection Section
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
IRT
Output Current of RT Pin
RI = 26kΩ
64
70
76
uA
1.015
1.065
1.115
V
VOTP-LATCH-OFF
Threshold Voltage for Over-Temperature
Protection.
TDOTP-LATCH
Over-Temperature Latch-Off Debounce.
VOTP-RESET
OTP Release Voltage (for non-latch-off version)
RI = 26kΩ
100
usec
VOTP-LATCH-
V
OFF
+ 0.1
RI Section
Symbol
Parameter
Test Condition
Min.
Typ.
Unit
36
kΩ
RINOR
RI Operating Range
RIMAX
Max. RI value for Protection
216
kΩ
RIMIN
Min. RI value for Protection
6
kΩ
© System General Corp.
Version 1.0(IAO33.0008.B0)
15.5
Max.
-6-
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Sep. 30, 2004
Product Specification
SG6846
Highly-Integrated Green-Mode PWM Controller
TYPICAL CHARACTERISTICS
Min. Opperating Voltage vs Temperature
Start-up Threshold Voltage vs Temperature
17.5
11.5
11.3
11.1
VTH-OFF (V)
VTH-ON (V)
17.0
16.5
16.0
10.9
10.7
10.5
10.3
10.1
9.9
9.7
9.5
15.5
-40
-25
-10
5
20
35
50
65
80
95
110
-40
125
-25
-10
5
50
65
80
95
110
125
Start-up Current vs VDD Voltage
Start-up Current vs Temperature
20
16.000
16
IDD-ST (uA)
15.500
15.000
14.500
12
8
4
14.000
0
13.500
-40
-25
-10
5
20
35
50
65
80
95
110
125
5
10
15
Temperature (℃)
20
VDD (V)
PWM Turn-on Threshold Voltage vs
Temperature
PWM Turn-off Threshold Voltage vs
Temperature
1.000
1.000
0.900
0.900
0.800
0.800
VIN-ON (V)
V IN-OFF (V)
35
Temperature (℃ )
Temperature (℃)
IDD-ST (uA)
20
0.700
0.600
0.700
0.600
0.500
0.500
0.400
0.400
-40
-25
-10
5
20
35
50
65
80
95
110
-40
125
© System General Corp.
Version 1.0(IAO33.0008.B0)
-25
-10
5
20
35
50
65
80
95
110
125
Temperature (℃ )
Temperature (℃ )
-7-
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Sep. 30, 2004
Product Specification
SG6846
Highly-Integrated Green-Mode PWM Controller
PWM Frequency vs FB Voltage (RI = 26KΩ)
PWM Frequency vs Temperature
PWM Frequency (Khz)
65.300
FOSC (Khz)
65.200
65.100
65.000
64.900
64.800
64.700
60
40
20
0
64.600
-40
-25
-10
5
20
35
50
65
80
95
110
125
1.5
1.6
1.7
1.8
Temperature (℃)
Current-limit Threshold vs VIN Voltage
2
2.1
2.2
2.3
2/3 Current-limit Threshold vs VIN Voltage
1
1
0.8
0.8
VTH-O (V)
VTH-P (V)
1.9
VFB (V)
0.6
0.4
0.6
0.4
0.2
0.2
0
0
1
1.5
2
2.5
1
3
1.5
2
2.5
3
VIN (V)
VIN (V)
OTP Threshold Voltage vs Temperature
Output Current of pin RT vs Temperature
1.115
78.000
77.000
1.095
VOTP-OFF (V)
IRT (uA)
76.000
75.000
74.000
73.000
72.000
1.075
1.055
1.035
71.000
1.015
70.000
-40
-25
-10
5
20
35
50
65
80
95
110
-40
125
-10
5
20
35
50
65
80
95
110
125
Temperature (℃ )
Temperature (℃ )
© System General Corp.
Version 1.0(IAO33.0008.B0)
-25
-8-
www.sg.com.tw
Sep. 30, 2004
Product Specification
SG6846
Highly-Integrated Green-Mode PWM Controller
OPERATION DESCRIPTION
Start-up Operation
The turn-on/turn-off thresholds are fixed internally
at 16.5V/10.5V. To enable the SG6846 during start-up,
the hold-up capacitor must first be charged to 16.5V
through the start-up resistor.
The hold-up capacitor will continue to supply VDD
before energy can be delivered from the auxiliary winding
of the main transformer. The VDD must not drop below
10.5V during this start-up process. This UVLO hysteresis
window ensures that the hold-up capacitor can adequately
supply VDD during start-up.
The typical start-up current is only 8uA. This allows
a high resistance, low-wattage start-up resistor to be used,
to minimize power loss. A 1.5 MΩ/0.25W, start-up
resistor and a 10uF/25V VDD hold-up capacitor would be
sufficient for a universal input range.
The required operating current has been reduced to
3.7mA. This enables higher efficiency and reduces the
VDD hold-up capacitance requirement.
Green-Mode Operation
The proprietary green-mode function provides
off-time modulation to continuously decrease the
switching frequency under light-load conditions.
Maximum on time is limited to provide protection against
abnormal conditions. To further reduce power
consumption under zero-load condition, the PWM
oscillator will be completely turned off, and the power
supply will enter burst-mode. After the PWM oscillator is
turned off, the IC’s supply voltage VDD will drop
gradually. Before the VDD voltage drops below the
UVLO threshold, the PWM oscillator will be turned on
again. This green-mode function dramatically reduces
power consumption under light-load and zero-load
conditions. Power supplies using the SG6846 can easily
meet even the most restrictive international regulations
regarding standby power consumption.
This current is used to determine the PWM frequency.
Increasing the resistance will decrease the amplitude of
the current source and reduce the PWM frequency. Using
a 26kΩ resistor Ri results in a corresponding 65kHz
switching frequency. The relationship between RI and the
switching frequency is:
fPWM (kHz) =
1690
Ri (kΩ )
---------------------------- (1)
If an open circuit or short circuit to ground occurs at the
RI pin, the internal protection circuit will immediately
shut down the controller.
Two-level Over-current Protection
The cycle-by-cycle current limiting will shut down
the PWM immediately when the switching current is over
the peak-current threshold. Additionally, when the
switching current is higher than 2/3 of the peak-current
threshold, the internal counter starts counting up. When
the switching current is lower than 2/3 of the peak current
threshold, the internal counter will count down. When the
total accumulated counting time is more than about 96ms
(Ri = 26kohm), the controller will be latched off.
This two-level OCP protection and up/down counter
are especially designed for SMPS with surge current
output such as those for printers, scanners, motor drivers,
etc.
Constant Output Power Limit
For constant output power limit over universal
input-voltage range, the peak-current threshold is
adjusted by the voltage of the VIN pin. Since the VIN pin
is connected to the rectified AC input line voltage through
the resistive divider, a higher line voltage will generate a
higher VIN voltage. The threshold voltage decreases as
the VIN voltage increases, making the max. output power
at high line input voltage equal to that at low line input.
Brownout Protection
Since the VIN pin is connected through a resistive
divider to the rectified AC input line voltage, it can also
be used for brownout protection. If the VIN voltage is less
A resistor connected from the RI pin to GND
than 0.72V, the PWM output will be shut off. As the VIN
generates a reference current source inside the SG6846.
© System General Corp.
-9www.sg.com.tw
Version 1.0(IAO33.0008.B0)
Sep. 30, 2004
Oscillator Operation
Product Specification
SG6846
Highly-Integrated Green-Mode PWM Controller
voltage over 0.92V, the PWM output will be turned on
again. The hysteresis window for ON/OFF is around
0.2V.
RT pin drops below 1.065V, the SG6846 will be turned
off. There are two options for the protection modes,
please see ORDER INFORMATION.
Noise immunity
VDD Over-voltage Protection
VDD over-voltage protection is built in to prevent
the controller from over-voltage destruction. When VDD
voltage is over 23.6V, the SG6846 is latched off.
Over-temperature Protection
An external NTC thermistor can be connected from
the RT pin to GND. The impedance of the NTC will
decrease at high temperatures. When the voltage of the
© System General Corp.
Version 1.0(IAO33.0008.B0)
- 10 -
Noise from the current sense or the control signal
may cause significant pulse width jitter, particularly in
continuous-conduction mode. Slope compensation helps
alleviate this problem. Good placement and layout
practices should be followed. The designer should
avoiding long PCB traces and component leads.
Compensation and filter components should be located
near the SG6846.
www.sg.com.tw
Sep. 30, 2004
Product Specification
SG6846
Highly-Integrated Green-Mode PWM Controller
REFERENCE CIRCUIT
Application circuit for 32V/16V output
R16
D4
1
R3
D1
L4
12
2
D3
7
1
9
3
11
2
C11
2
R17
P16V
P16V L2
1
C5
R11
+
2
C17+
3
1
C3
1
+
32V
10
D2
2
21
2
1
R4
32V
C13
+
1
C2
R9
C12
+
C14
2
R2
C16+
3
6
2
P7
R12 C4
1
3
+
P32V
P32V L1
2
1
R8
R1
13
2
5
2
1
2
4
4
1
1
CX2
CY2
3
1
P2
TX1
2
2
VZ1
LF1
BD1
1
CX1LF2
3
4
CY1
2
RT1
2
F1
t
P1
+
16V 16V
C15
+
2
1
+
R5
4
FB
VDD
VIN
1
Q1
R13
1
2
8
3
2
3
C1
GATE
SENSE
RI
RT
7
5
L3
R6
6
R10
C6
1
FB
GND
2
U1
1
1
1
D5
R14
NTC1
R7
P16V
P16V
P16V
1
FB
4
R15
FB
C7
R18
K
2
3
U2
P32V
P16V
C9
R
R20
R21
A
U3
P32V
R19
BOM
PART NO.
VALUE
PART NO.
VALUE
PART NO.
VALUE
R1, R2, R3, R4
470KΩ +/-5%
C4
103 P 630V
D3
FR103 1.0A 200V
R8, R9
S1MΩ +/-1%
C10,C11
102 P 1KV
BD1
DBL406G
R5
16K2Ω +/-1%
C6,C7
102 P 50V
D4
BYT28-300
R15
1K5Ω +/-5%
C9
222 P 50V
D5
BYV32-150
R13
10Ω +/-5%
C14,C17
470u 25V
F1
250V4A QUICK
R18
4K7Ω +/-5%
C15
220u 25V
L1,L2
1.8uH
R21
15KΩ +/-1%
C13,C16
220u 50V
L4
10uH
R7
27KΩ +/-5%
C2
150u 400V
U3
TL431 +/-1%
R6
330Ω +/-1%
C1
4u7 50V
U1
SG 6846
R19
102KΩ +/-1%
C3
10u 50V
U2
PC817
R14
0Ω22 +/-5%
CX1
X1 0.47u 275V
Q1
7NB60
R16, R17
1W 20Ω +/-5%
C8
Y2 222P 250V
TX1
EI-33
R11
20KΩ +/-5%
C5
100u 50V
RT1
SCK053
R12
100KΩ +/-5%
CX2
X2 0.1uF 275V
VZ1
14ψ 470V
R20
887KΩ +/-1%
D1
1N4148
R22
10KΩ +/-1%
D2
BYV95C
© System General Corp.
Version 1.0(IAO33.0008.B0)
- 11 -
www.sg.com.tw
Sep. 30, 2004
Product Specification
SG6846
Highly-Integrated Green-Mode PWM Controller
PACKAGE INFORMATION
DIP-8 Outline Dimensions
D
Θ°
5
E1
8
B
A
A2
4
A1
1
e
E
L
b1
e
b
Dimension
Symbol
A
A1
A2
b
b1
D
E
E1
e
L
eB
θ˚
Millimeter
Min.
0.381
3.175
9.017
6.223
2.921
8.509
0˚
© System General Corp.
Version 1.0(IAO33.0008.B0)
Inch
Min.
Typ.
Max.
5.334
3.302
1.524
0.457
9.271
7.620
6.350
2.540
3.302
9.017
7˚
3.429
0.015
0.125
10.160
0.355
6.477
0.245
3.810
9.525
15˚
0.115
0.335
0˚
- 12 -
Typ.
Max.
0.210
0.130
0.060
0.018
0.365
0.300
0.250
0.100
0.130
0.355
7˚
0.135
0.400
0.255
0.150
0.375
15˚
www.sg.com.tw
Sep. 30, 2004
Product Specification
SG6846
Highly-Integrated Green-Mode PWM Controller
SOP-8 Outline Dimensions
C
5
E
H
8
F
1
4
b
e
D
Θ
A1
L
A
Dimension:
Symbol
A
A1
b
c
D
E
e
F
H
L
θ˚
Millimeter
Min.
1.346
0.101
© System General Corp.
Version 1.0(IAO33.0008.B0)
Typ.
Max.
1.752
0.254
Inch
Min.
0.053
0.004
0.406
0.203
4.648
3.810
Max.
0.069
0.010
0.016
0.008
4.978
3.987
0.183
0.150
1.270
0.196
0.157
0.050
0.381X45˚
5.791
0.406
0˚
Typ.
0.015X45˚
6.197
1.270
8˚
- 13 -
0.228
0.016
0˚
0.244
0.050
8˚
www.sg.com.tw
Sep. 30, 2004
Product Specification
SG6846
Highly-Integrated Green-Mode PWM Controller
DISCLAIMERS
LIFE SUPPORT
System General’s products are not designed to be used as components in devices intended to support or sustain human
life. Use of System General’s products in components intended for surgical implant into the body, or other applications in
which failure of System General’s products could create a situation where personal death or injury may occur, is not
authorized without the express written approval of System General’s Chief Executive Officer. System General will not be
held liable for any damages or claims resulting from the use of its products in medical applications.
MILITARY
System General's products are not designed for use in military applications. Use of System General’s products in
military applications is not authorized without the express written approval of System General’s Chief Executive Officer.
System General will not be held liable for any damages or claims resulting from the use of its products in military
applications.
RIGHT TO MAKE CHANGES
System General reserves the right to change this document and/or this product without notice. Customers are advised
to consult their System General sales representative before ordering.
© System General Corp.
Version 1.0(IAO33.0008.B0)
- 14 -
www.sg.com.tw
Sep. 30, 2004