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PDF SG6849 Data sheet ( Hoja de datos )
| Número de pieza | SG6849 | |
| Descripción | Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback | |
| Fabricantes | System General | |
| Logotipo |  |
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Product Specification
Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback
SG6849
FEATURES
Linearly Decreasing PWM Frequency
Green-Mode under Light-Load and Zero-Load
Conditions
Constant Voltage (CV) and Constant Current (CC)
No Secondary Feedback
Low Startup Current (5uA)
Low Operating Current (3.6mA)
Leading-Edge Blanking
Constant Power Limit
Universal AC Input Range
Synchronized Slope Compensation
150°C OTP Sensor with Hysteresis
VDD Over Voltage Clamping
Cycle-by-Cycle Current Limiting
Under Voltage Lockout (UVLO)
Fixed PWM Frequency (65kHz/100kHz)
Gate Output Maximum Voltage Clamped at 16.7V
Small SOT-26 Package
APPLICATIONS
Low-power 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, consumer
electronics, and PC 5V standby-power.
Replacements for linear transformers and RCC
SMPS.
DESCRIPTION
This highly integrated PWM controller provides several
features to enhance the performance of low power flyback
converters. To minimize standby power consumption, the
proprietary green-mode function provides off-time
modulation to linearly decrease the switching frequency
under light-load and zero-load conditions. This
green-mode function enables the power supply to easily
meet international power conservation requirements. The
supply voltage VDD is also used for feedback
compensation, to regulate the output voltage without
requiring a conventional TL431 and a photo-coupler.
Another advantage of the SG6849 is that the typical
startup current is only 5uA, while the typical operating
current can be as low as 3.6mA. A large startup resistance
could be used to achieve even higher power conversion
efficiency. Built-in synchronized slope compensation
maintains the stability of peak current-mode control.
Proprietary internal compensation ensures constant output
power limiting over a universal range of AC input
voltages, from 90VAC to 264VAC.The SG6849 provides
many protection functions. Pulse-by-pulse current
limiting ensures a constant output current, even if a short
circuit occurs. Also, the internal protection circuit will
disable PWM output, if VDD exceeds 22.7V. The gate
output is clamped at 16.7V to protect the power MOS
from over-voltage damage. The built-in over temperature
protection (OTP) function will shutdown the controller at
150°C with a 20°C hysteresis. The SG6849 is designed to
provide a low-cost total solution for flyback converters. It
is available in a small footprint, 6-pin, SOT-26 package.
TYPICAL IC APPLICATION
V IN
R IN
C IN
D1
VDD
Q1
G ATE
W AUX
SENSE
GND
RS
DO
CO
VO
© System General Corp.
Version 1.0(IRO33.0002.B3)
-1-
www.sg.com.tw
Dec.29, 2003
1 page  
Product Specification
Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback
SG6849
Current Sense Section
Symbol Parameter
TPD
Propagation Delay
Test Condition
VDD = 20V
Current Limiting Valley Threshold Voltage for 65kHz VDD = 15V
VTH,VA
VDD = 10V
VDD = 20V
Current Limiting Valley Threshold Voltage for 100kHz VDD = 15V
VDD = 10V
Min.
0.84
0.72
0.58
0.76
0.65
0.52
Typ.
100
0.89
0.77
0.63
0.81
0.70
0.57
Max.
0.94
0.82
0.68
0.86
0.75
0.62
Unit
ns
V
V
V
V
V
V
TON
TOFF
VLIMIT Ramp
VTH,FT
High-Line
Sense Voltage
Low-Line Sense
Voltage
VTH,VA
0.77V
0V
T1
T2
Oscillator Section
Symbol Parameter
Test Condition Min. Typ. Max.
FOSC
SG6849–65 Frequency
60 65 70
FOSC
SG6849–100 Frequency
92 100 108
FOSC-G-BK
Green-Mode Burst Back Frequency*
20 25 30
FOSC-G-OFF
Green-Mode OFF Frequency*
0
IFB-G-OFF
Green-Mode OFF FB Input Current
0.9 1.15 1.4
FDV
Frequency Variation versus VDD Deviation
VDD = 10 to 20V
2
VDD-TH-G
VDD-Low Threshold Voltage for Exiting Green-Mode
OFF
VDD
OFF+1.0
VDD
OFF+1.5
VDD
OFF+2.0
*Please see the “Green-Mode Burst Back (FOSC-G-BK) and Green-Mode OFF Frequency (FOSC-G-OFF) vs. VDD” curves.
Unit
kHz
kHz
kHz
kHz
mA
%
V
© System General Corp.
Version 1.0(IRO33.0002.B3)
-5-
www.sg.com.tw
Dec.29, 2003
5 Page 
Product Specification
Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback
SG6849
REFERENCE CIRCUIT
3W Flyback 5V/0.6A Circuit, without Secondary-Side Feedback
L F1
L1
12
CX1
2-
BD1
+4
C1
+ C2
R1
C3 R3
R5 R4
T1
N 10
R2
D1 9
U4
1 GND
GATE
2 FB
VDD
3 NC SENSE
SG6849
6
5
4
R7
1 Q1
R6
8
5
7
D4
1,2 2
1
L2
12
R10 C7
C8 +
D5 + C9
3,4
R8
+ C4
D2
12
CY1
VO
GND
BOM
Symbol
BD1
CX1 (Option)
CY1 (Option)
C2
C1
C3
C4
C7 (Option)
C8
C9
D1
D2
D4
D5 (Option)
F1
Component
BD 1A/500V
YC 472pF/400V (Y1)
YC 102pF/400V (Y1)
EC 10uF/400V 105℃
CC 103pF/500V
CC 1000pF/500V
EC 10uF/50V
CC 102pF/100V 1206
EC 470uF/10V 105℃
EC 220uF/10V 105℃
Diode FRI07
Diode FR102
Diode SB360
ZD 6.8V 0.5W
R 1Ω/0.5W
Symbol
L1
L2
Q1
R1,R2
R3,R4
R5
R6
R7
R8
R10 (Option)
T1
U4
Component
20mH 6*8mm
10uH 6mm
MOSFET 1A/600V
R 750kΩ 1206
R 47kΩ 1206
R 47Ω 1206
R 4.7Ω 1206
R 100Ω 0805
R 10Ω 1206
R 10Ω 1206
EE-16
IC SG6849 (Green PWM IC)
© System General Corp.
Version 1.0(IRO33.0002.B3)
- 11 -
www.sg.com.tw
Dec.29, 2003
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet SG6849.PDF ] | |
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