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PDF SG3845G Data sheet ( Hoja de datos )
| Número de pieza | SG3845G | |
| Descripción | BiCMOS Green-Mode PWM Controllers | |
| Fabricantes | System General | |
| Logotipo |  |
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BiCMOS Green-Mode PWM Controllers
Product Specification
SG3842G/ 3843G/ 3844G/ 3845G
FEATURES
384x series pin-to-pin compatible
Linearly decreasing PWM frequency
Burst-mode at low/zero load
5uA start-up current
5mA operating current
Vcc over voltage protection
Cycle-by-cycle current limiting
Zero cross-conduction
Slew rate controlled high current totem pole output
Fast current sense propagation delay
Under voltage lockout (UVLO) with hysteresis
APPLICATIONS
Switching mode power supplies
Power converters
DESCRIPTION
The SG348xG series of current-mode PWM
controllers combines high performance with Green-mode
power saving features. SG348xG controllers are fully
pin-to-pin compatible with bipolar UC384x devices, but
they have improved features and functionality. SG384xG
series controllers are compatible with the BiCMOS
fabrication process, enabling the use of low start-up
current and operating currents. This feature further
improves power conversion efficiency. The minimal
start-up current has been reduced to 5uA, and the
minimum operating current has been reduced to 5mA.
Each SG384xG has a slew rate controlled high current
totem pole output, ideally suited for driving a power
MOSFET while keeping EMI low.
The current-sense propagation delay is typically
50ns, resulting in significantly more effective constant
power protection. During normal operation, a SG384xG
controller acts as a fixed frequency PWM controller. The
PWM frequency can be easily programmed by changing
external RT and CT values. The SG384xG includes two
Green-mode functions that dramatically reduce power
usage, helping the power supply comply with the latest
international power saving guidelines. To cut power
consumption under light load conditions, the controller’s
Green-mode function will linearly decrease the PWM
frequency in response to decreases in the output load.
Under ultra light-load/zero-load conditions, the RT/CT
PWM oscillator periodically shuts down, and enters into
Burst-mode. This causes the IC’s supply voltage to begin
gradually dropping. Just before the supply voltage drops
below the UVLO voltage threshold, the RT/CT PWM
oscillator turns back on, to prevent the supply voltage
from going below the UVLO voltage.
SG384xG controllers also come with Over Voltage
Protection (OVP). This shuts down PWM output if the
supply voltage ever exceeds 27V. The SG384xG series
comes in 8-pin DIP and SOP packages.
TYPICAL APPLICATION
Green-mode Operation
Oscillator Frequency vs. COMP
From bridge rectifier
120~ 380VDC
RIN
1.5M
VCC
COMP
Rac OUTPUT
10k
VREF
C21
RT 0.1u SG384x
10k
SENSE
CT
3.3n
VFB
GND
From auxiliary winding
CIN
10u
R41
100
R42
1k
C25 RS
100p 0.3
© System General Corp.
Version D.2 ( IRO33.0007.B1)
-1-
Oscillator Frequency (Fosc) vs COMP Voltage
60
50
40
30
20
10
0
1 1.5 2 2.5
COMP VOLTAGE (V)
3
www.sg.com.tw
Apr.22,2003
1 page  
BiCMOS Green-Mode PWM Controllers
Current Sense Section
Symbol Parameter
AV Current sense input voltage gain (n)
IIB
TPD
VTH(IS)
Input bias current
Delay to output
Maximum input signal
Output Section
Symbol
Vol
Parameter
Output voltage low
Voh Output voltage high
Tr Rising time
Tf Falling time
Under-Voltage Lockout Section
Symbol Parameter
VTH(ON)
Start threshold voltage
VTH(OFF)
Minimum operating voltage
PWM Section
Symbol Parameter
DCY(MAX)
Maximum duty cycle
DCY(MIN)
Minimum duty cycle
Total Standby Current Section
Symbol Parameter
ICC ST
Start-up current
ICC OP
Vz
VP
Operating supply current
Power supply zener voltage
Power supply protection voltage
Product Specification
SG3842G/ 3843G/ 3844G/ 3845G
Test Condition
SG3842G, SG3844G
SG3842G2, SG3844G2,
SG3843G, SG3845G
-
Ta=25°C
-
Min.
4.60
2.76
-
-
0.9
Typ.
5.00
3.00
-1
50
1.0
Max.
5.40
3.24
-5
150
1.1
Unit
V/V
V/V
uA
nS
V
Test Condition
Vcc=15V, Io=20mA
Vcc=15V, Io=20mA
Ta=25°C, CL=1nF
Ta=25°C, CL=1nF
Min.
-
13
-
-
Typ.
-
-
50
50
Max.
0.5
-
150
150
Unit
V
V
nS
nS
Test Condition
SG3842G, SG3844G
SG3843G, SG3845G
SG3842G, SG3844G
SG3843G, SG3845G
Min.
15
8.4
9
7.6
Typ.
16
8.9
10
8.1
Max.
17
9.4
11
8.6
Unit
V
V
V
V
Test Condition
SG3842G, SG3842G2,
SG3843G
SG3844G, SG3844G2,
SG3845G
FB=5V, COMP=Open
Min.
90
45
-
Typ.
95
47
-
Max.
98
49
0
Unit
%
%
%
Test Condition
Min.
SG3842G, SG3844G
Vcc=15V
-
SG3843G, SG3845G Vcc=8V -
FB=SENSE=0V, VDD=15V,
CL=1000pF
-
Icc=10mA
25
Typ.
5
3
5.0
28
27
Max.
15
10
6.5
-
Unit
uA
uA
mA
V
V
© System General Corp.
Version D.2 ( IRO33.0007.B1)
-5-
www.sg.com.tw
Apr.22,2003
5 Page 
BiCMOS Green-Mode PWM Controllers
Start-up Current vs Vcc Supply Voltage
9
8
T emperature=25℃
7
6
5
4
3
2
1
0
0 5 10 15 20 25
Vcc VOLT AGE (V)
Oscillator Frequency (Fosc) vs COMP Voltage
60
50
40
30
20
10
0
1
Vc c =15V
T e mpe ra ture=25 ℃
1.5 2 2.5
COMP VOLTAGE(V)
3
Product Specification
SG3842G/ 3843G/ 3844G/ 3845G
Fosc-G (Green-mode) vs Vcc
30
25
COMP=1.4V
20 Temperature=25℃
15
10
5
0
7 8 9 10 11 12 13 14
Vcc VOLTAGE (V)
© System General Corp.
Version D.2 ( IRO33.0007.B1)
- 11 -
www.sg.com.tw
Apr.22,2003
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet SG3845G.PDF ] | |
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