SG3843G [ETC]
BiCMOS Green-Mode PWM Controllers; BiCMOS工艺绿色模式PWM控制器
| 型号： | SG3843G |
| 厂家： | 
ETC |
| 描述： | BiCMOS Green-Mode PWM Controllers |
| 文件： | 总19页 (文件大小：351K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
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.
FEATURES
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
384x series pin-to-pin compatible
Linearly decreasing PWM frequency
Burst-mode at low/zero load
5uA start-up current
5mA operating current
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.
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
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
From auxiliary winding
Oscillator Frequency (Fosc) vs COMP Voltage
CIN
RIN
60
10u
1.5M
50
40
30
20
10
0
VCC
R41
100
COMP
VREF
Rac
10k
OUTPUT
C21
0.1u
R42
1k
RT
SG384x
10k
SENSE
RS
C25
CT
3.3n
0.3
100p
VFB
1
1.5
2
2.5
3
GND
COMP VOLTAGE (V)
© System General Corp.
Version 1.4 ( IRO33.0007.B3)
- 1 -
www.sg.com.tw
Jun.28,2004
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
MARKING INFORMATION
PIN CONFIGURATION
8
Z: 2, 3
T: D = DIP, S = SOP
SG384ZGTP
A
VREF
VCC
8
COMP
VFB
1
2
P : Z = Lead Free
7
6
5
Null=Regular Package
XXXXXXX: Wafer Lot
YY: Year; WW: Week
V: Assembly Location
SENSE
RT/CT
OUTPUT
GND
3
4
1
ORDERING INFORMATION
UVLO
Part Number
AV
5.0
3.0
3.0
5.0
3.0
3.0
Package
Start threshold
Stop threshold
SG3842GAD
SG3842GAS
SG3842G2AD
SG3842G2AS
SG3843GAD
SG3843GAS
SG3842GADZ
SG3842GASZ
SG3842G2ADZ
SG3842G2ASZ
SG3843GADZ
SG3843GASZ
8-Pin DIP
8-Pin SOP
8-Pin DIP
8-Pin SOP
8-Pin DIP
8-Pin SOP
8-Pin DIP(Lead Free)
8-Pin SOP( Lead Free)
8-Pin DIP(Lead Free)
8-Pin SOP( Lead Free)
8-Pin DIP( Lead Free)
8-Pin SOP( Lead Free)
16V±1V
10V±1V
8.9V±0.5V
16V±1V
8.1V±0.5V
10V±1V
8.9V±0.5V
8.1V±0.5V
PIN DESCRIPTIONS
Pin No. Symbol
Function
Description
Output of the Error Amplifier and input to the PWM comparator. It is used for feedback
1
COMP
VFB
Compensation
Feedback
loop compensation.
Inverting input of the Error Amplifier. It is normally connected to the switching power
supply output through a resistor divider.
2
3
Current sense comparator input. It is internally set to 1V maximum. A voltage proportional
SENSE
Current sense
to the inductor current is connected to this input.
Oscillator RC timing connection. Connecting a resistor RT from this pin to Vref, and a
capacitor CT from this pin to ground, programs the oscillator frequency and the maximum
output duty cycle.
4
RT/CT
GND
Oscillator control
Ground
5
6
7
8
This pin is the combined control circuit ground and power ground.
High-power, totem-pole driver output. This output drives the gate of a power MOSFET.
OUTPUT Output
VCC
VREF
Power supply
Supply voltage input.
Reference voltage 5V-reference voltage output.
© System General Corp.
- 2 -
www.sg.com.tw
Jun.28,2004
Version 1.4 ( IRO33.0007.B3)
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
BLOCK DIAGRAM
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
Test Condition
Value
Unit
Low impedance source
Zener clamp
25
28
10
Vcc
Supply voltage
Zener current
FB/SENSE terminal input voltage
Error amplifier sink current
V
Iz
mA
V
mA
VIN
ISINK
FB, SENSE
-0.3 to 5.5V
10
at Ta<50°C DIP
SOP
800
Pd
Power dissipation
mW
400
Junction-air
DIP
82.5
R
Θ
Thermal resistance
°C/W
j-a
SOP
141
TJ
Ta
Tstg
TL
Operating junction temperature
Operating ambient temperature
Storage temperature range
-
+150
-40 to 125
-65 to +150
260
°C
°C
°C
-
-
10 sec
20 sec
DIP
Lead temperature (Soldering)
°C
SOP
220
ESD Capability, HBM model
ESD Capability, Machine model
3.0
kV
V
200
© System General Corp.
- 3 -
www.sg.com.tw
Jun.28,2004
Version 1.4 ( IRO33.0007.B3)
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
OPERATING CONDITIONS
Symbol
Parameter
Min.
Max.
Unit
Vcc
Supply voltage
-
20
V
CT
RT
fOSC
Ta
Oscillation timing capacitor
Oscillation timing resistor
Oscillation frequency
0.47
2.0
10
10
nF
kΩ
100
500
105
kHz
°C
Operating ambient temperature
-40
ELECTRICAL CHARACTERISTICS
Reference Voltage Section
Symbol
Vref
Line
Load
Vtc
Parameter
Test Condition
Min.
Typ.
5.0
2
Max.
5.25
20
Unit
V
Reference output voltage
Line regulation
Ta=25°C, Io=1mA
4.75
Vcc=10 to 20V
Io=1mA to 20mA
-
mV
mV
mV/°C
mA
V
Load current regulation
Temperature stability
Short-circuit output current
Total output variation
Output noise voltage
Long term stability
-
20
50
-
-
-
0.5
-85
5.0
50
-
Ios
-30
-180
5.25
-
Vref
Vn
Line, Load, Temperature
f=10Hz to 10kHz , Ta=25°C
Ta=125°C for 1000 hours
4.75
-
-
uV
mV
S
5
25
Oscillator Section (VFB=0V, SENSE=0V)
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
SG3842G, SG3843G
49
52
55
kHz
FOSC
Oscillator frequency
SG3842G2
49
8
52
12
54
16
kHz
kHz
V
FOSC-G
Vcomp,H
Green-mode frequency (note 1)
Vsense=0V
SG3842G
2.60
2.00
1.40
1.30
0.2
Comp Voltage that initiates Green-mode
SG3842G2, SG3843G
SG3842G
V
V
Vcomp,L
Comp Voltage that shuts down PWM
SG3842G2, SG3843G
Vcc=10 to 20V
Ta=-40 to 85°C
Ta=25°C
V
fdv
Frequency change with Vcc
Frequency change with temp.
Discharge current
-
1
%
fdt
-
0.02
9
-
%/°C
mA
IDISCHG
7
12
Note 1: FOSC-G is the last PWM frequency before completely turned off @ Vcc=15V
Error Amplifier Section
Symbol
Parameter
Test Condition
Min.
2.45
-
45
0.7
50
-0.8
2
6
-
Typ.
2.5
-
Max.
Unit
V
VFB
Input voltage
Comp=2.5V
2.55
Iib
Input bias current
Open-loop voltage gain
Unity gain bandwidth
Power supply rejection ratio
Output source current
Output sink current
Output voltage
-
0.1
uA
Avol
-
55
1.2
-
-
dB
BW
-
-
MHz
dB
PSRR
Isource
Isink
-
-
FB=2.3V,COMP=0V
FB=2.7V,COMP=1V
FB=2.3V, RL=15K to GND
FB=2.7V, RL=15K to VREF
-1.8
6.5
6.6
-
-3
mA
mA
V
-
VH COMP
VL COMP
-
Output voltage
700
mV
Current Sense Section
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
AV
Current sense input voltage gain (n)
SG3842G
4.60
5.00
5.40
V/V
© System General Corp.
- 4 -
www.sg.com.tw
Version 1.4 ( IRO33.0007.B3)
Jun.28,2004
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
SG3842G2,SG3843G
2.76
3.00
-1
3.24
-5
150
1.1
V/V
uA
nS
V
IIB
TPD
VTH(IS)
Input bias current
Delay to output
Maximum input signal
-
-
Ta=25°C
-
-
50
0.9
1.0
Output Section
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
Vol
Output voltage low
Vcc=15V, Io=20mA
-
-
0.5
V
Voh
Output voltage high
Vcc=15V, Io=20mA
Ta=25°C, CL=1nF
Ta=25°C, CL=1nF
13
-
50
50
-
V
nS
nS
Tr
Rising time
-
150
150
Tf
Falling time
-
Under-Voltage Lockout Section
Symbol
Parameter
Test Condition
SG3842G
Min.
15
Typ.
16
Max.
17
Unit
V
VTH(ON)
Start threshold voltage
SG3843G
8.4
9
8.9
10
9.4
V
SG3842G
SG3843G
11
8.6
V
V
VTH(OFF)
Minimum operating voltage
7.6
8.1
PWM Section
Symbol
DCY(MAX)
DCY(MIN)
Parameter
Test Condition
Min.
Typ.
Max.
Unit
SG3842G, SG3842G2,
SG3843G
90
95
98
%
Maximum duty cycle
Minimum duty cycle
FB=5V, COMP=Open
-
-
0
%
Total Standby Current Section
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
15
Unit
uA
SG3842G, Vcc=15V
SG3843G, Vcc=8V
FB=SENSE=0V, VDD=15V,
CL=1000pF
-
-
5
3
ICC ST
Start-up current
10
uA
ICC OP
Operating supply current
-
5.0
6.5
-
mA
Vz
VP
Power supply zener voltage
Power supply protection voltage
Icc=10mA
25
28
27
V
V
© System General Corp.
- 5 -
www.sg.com.tw
Jun.28,2004
Version 1.4 ( IRO33.0007.B3)
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
TYPICAL CHARACTERISTICS
SG3842G
CC,ST
Start-up Current (I
CC,OP
) vs Temperature
Operating Supply Current (I
) vs Temperature
4.0
3.5
3.0
2.5
2.0
1.5
1.0
6.50
Vcc=14.0V
Vcc=15.0V
6.00
5.50
5.00
4.50
4.00
3.50
3.00
-40 -25 -10
5
20
35
50
65
80
95
110 125
-40 -25 -10
5
20
35
50
65
80
95 110 125
TEMPERATURE (℃)
TEMPERATURE (℃)
REF
FB
Reference Voltage (V ) vs Temperature
Error Amp Input Voltage (V ) vs Temperature
5.10
5.05
5.00
4.95
4.90
4.85
4.80
2.53
2.52
2.51
2.50
2.49
2.48
2.47
Vcc=15.0V
Vcc=15.0V
-40 -25 -10
5
20
35
50
65
)
80
95 110 125
-40 -25 -10
5
20
35
50
65
)
80
95 110 125
TEMPERATURE (
TEMPERATURE (
℃
℃
Oscillator Frequency (Fosc) vs Temperature
MAX
Maximum Duty Cycle (D
) vs Temperature
54.0
53.0
52.0
51.0
50.0
49.0
96.00
95.50
95.00
94.50
94.00
Vcc=15.0V
Vcc=15.0V
-40 -25 -10
5
20
35
50
65
)
80
95 110 125
-40 -25 -10
5
20
35
50
65
80
95 110 125
TEMPERATURE (
℃
TEMPERATURE (℃)
© System General Corp.
Version 1.4 ( IRO33.0007.B3)
- 6 -
www.sg.com.tw
Jun.28,2004
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
DISCH
TH
Oscillator Discharge Current (I
) vs
Start Threshold Voltage (V ) vs Temperature
Temperature
17.00
16.50
16.00
15.50
15.00
14.50
14.00
9.0
8.5
8.0
7.5
7.0
6.5
Vcc=15.0V
-40 -25 -10
5
20
35
50
65
)
80
95 110 125
-40 -25 -10
5
20
35
50
65
)
80
95
110 125
TEMPERATURE (
℃
TEMPERATURE (
℃
Minimum Operating Voltage (Vcc,min) vs
Temperature
Output Voltage Low @ 20mA (Vol) vs Temperature
0.200
10.4
10.2
10.0
9.8
0.150
0.100
0.050
0.000
9.6
9.4
9.2
9.0
-40 -25 -10
5
20
35
50
65
80
95 110 125
-40 -25 -10
5
20
35
50
65
)
80
95 110 125
TEMPERATURE (
)
℃
TEMPERATURE (
℃
Output Voltage High @ Vcc=15V (Voh) vs
Temperature
Start-up Current vs Vcc Supply Voltage
4.0
3.0
2.0
1.0
0.0
15.00
14.98
14.96
14.94
14.92
14.90
14.88
14.86
14.84
14.82
14.80
Temperature=25℃
Vcc=15.0V
0
2
4
6
8
10
12
14
16
-40 -25 -10
5
20
35
50
65
80
95 110 125
Vcc VOLTAGE (V)
TEMPERATURE (℃)
© System General Corp.
Version 1.4 ( IRO33.0007.B3)
- 7 -
www.sg.com.tw
Jun.28,2004
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
Fosc-G (Green mode) vs Vcc
Vcc Current vs Vcc Supply Voltage
6
50
40
30
20
10
0
5
Temperature=25℃
COMP=1.4V
4
3
2
1
0
Temperature=25℃
0
3
6
9
12
15
18
21
24
27
9
10
11
12
13
14
Vcc VOLTAGE (V)
Vcc VOLTAGE (V)
Oscillator Frequency (Fosc) vs COMP Voltage
60
50
40
30
20
10
0
VCC=15V
Temperature=25℃
1
1.5
2
2.5
3
COMP VOLTAGE (V)
© System General Corp.
- 8 -
www.sg.com.tw
Jun.28,2004
Version 1.4 ( IRO33.0007.B3)
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
SG3843G
Start-up Current (ICC,ST) vs Temperature
Operating Supply Current (ICC,OP) vs
Temperature
5.0
4.5
6.5
6.0
5.5
5.0
4.5
Vcc=7.76V
4.0
Vcc=15.0V
3.5
3.0
2.5
2.0
4.0
3.5
1.5
1.0
-40
-25 -10
5
20
35
50
65
)
80
95 110 125
-40 -25 -10
5
20
35
50
65
80
95 110 125
℃
TEMPERATURE (
℃
TEMPERATURE (
)
Reference Voltage (VREF) vs Temperature
Error Amp Input Voltage (VFB) vs Temperature
2.53
2.52
2.51
2.50
2.49
2.48
2.47
5.25
5.20
5.15
5.10
5.05
5.00
4.95
4.90
4.85
4.80
4.75
Vcc=15.0V
Vcc=15.0V
-40 -25 -10
5
20
35
50
65
80
95 110 125
-40 -25 -10
5
20
35
50
65
80
95 110 125
℃
TEMPERATURE (
)
℃
TEMPERATURE (
)
Maximum Duty Cycle (DMAX) vs Temperature
Oscillator Frequency (FOSC) vs Temperature
61.0
59.0
57.0
55.0
53.0
96.00
95.50
95.00
94.50
94.00
Vcc=13.0V
Vcc=13.0V
51.0
49.0
47.0
45.0
-40 -25 -10
5
20
35
50
65
80
95 110 125
-40 -25 -10
5
20
35
50
65
80
95 110 125
℃
℃
TEMPERATURE ( )
TEMPERATURE (
)
© System General Corp.
- 9 -
www.sg.com.tw
Jun.28,2004
Version 1.4 ( IRO33.0007.B3)
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
Oscillator Discharge Current (IDISCH) vs
Temperature
Start Threshold Voltage (VTH(ON)) vs Temperature
9.20
9.10
9.00
8.90
8.80
8.70
8.60
8.50
8.40
8.30
8.20
9.0
Vcc=15.0V
8.5
8.0
7.5
7.0
6.5
-40 -25 -10
5
20
35
50
65
80
95 110 125
-40 -25
-10
5
20
35
50
65
80
95
110 125
℃
TEMPERATURE (
)
℃
TEMPERATURE (
)
Minimum Operation Voltage (VTH(OFF)) vs
Temperature
Output Voltage Low @ 20mA(Vol) vs Temperature
0.20
8.25
8.20
8.15
8.10
8.05
8.00
0.15
0.10
0.05
0.00
7.95
-40 -25
-10
5
20
35
50
65
80
95
110 125
-40 -25 -10
5
20 35
50 65 80 95 110 125
℃
TEMPERATURE (
)
℃
TEMPERATURE (
)
Output Voltage High @ Vcc=15V (Voh) vs
Temperature
Start-up Current vs Vcc Supply Voltage
7
6
5
4
3
2
15.00
14.98
14.96
℃
Temperature=25
14.94
14.92
14.90
14.88
14.86
14.84
14.82
14.80
1
0
0
1
2
3
4
5
6
7
8
-40
-25
-10
5
20
35
50
65
80
95
110 125
℃
TEMPERATURE (
)
Vcc VOLTAGE (V)
© System General Corp.
- 10 -
www.sg.com.tw
Jun.28,2004
Version 1.4 ( IRO33.0007.B3)
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
Start-up Current vs Vcc Supply Voltage
Fosc-G (Green-mode) vs Vcc
30
25
20
15
10
5
9
8
℃
Temperature=25
COMP=1.4V
Temperature=25
7
6
℃
5
4
3
2
1
0
0
7
8
9
10
11
12
13
14
0
5
10
15
20
25
Vcc VOLTAGE (V)
Vcc VOLTAGE (V)
Oscillator Frequency (Fosc) vs COMP Voltage
60
50
40
30
20
10
0
Vcc=15V
Temperature=25
℃
1
1.5
2
2.5
3
COMP VOLTAGE(V)
© System General Corp.
- 11 -
www.sg.com.tw
Jun.28,2004
Version 1.4 ( IRO33.0007.B3)
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
to a pin, but it is internally biased to a fixed 2.5V ± 2%
voltage.
OPERATION DESCRIPTION
SG384xG devices have many advantages over traditional
384x devices and are completely pin-to-pin compatible
with them. The following descriptions highlight the
advantages and the differences of the SG384xGA designs.
Current Sensing and PWM Limiting
The SG384xG current-sense input is designed for
current-mode control. Current-to-voltage conversion is
done externally through the current-sense resistor Rs.
Under normal operation, the COMP voltage determines
the peak-voltage across Rs. VCOMP is the voltage at the pin
COMP and n is the current-sense input voltage gain.
Start-up Current
The required start-up current is typically only 5uA. This
ultra-low start-up current allows designers to supply the
start-up power required by the SG384xG using a
high-resistance and a low-wattage start-up resistor. For
example, an application using wide input range
(100VAC~240VAC) AC-to-DC power adapter could work
with a 1.5 MΩ/0.25W resistor, and a 10uF/25V Vcc
hold-up capacitor.
VCOMP −1.4
=
I pk
n*×RS
*n = is typically 5 (4.60 ~ 5.40) for the SG3842G standard
versions. n = 3 typically (2.76 ~ 3.24) for the SG3842G2,
and the SG3843G models.
Operating Current
This feature is compatible with general 384x series
products. A higher n value attenuates the feedback and
ensures loop stability under light-load conditions. The
inverting input to the SG384xG current-sense comparator
is internally clamped to 1V.
The operating current has been reduced to 5.0mA. This
low operating current results in higher efficiency and
reduces the required Vcc hold-up capacitance.
Oscillator Operation
Under Voltage Lockout (UVLO)
The resistor RT and the capacitor CT, both connected to
the pin RT/CT, determine the oscillation frequency. The
capacitor CT is normally charged to 2.9V through the
resistor RT, which is connected to a 5V reference voltage
and discharged to 1.3V by a built-in constant current sink.
The dead-time is generated during the discharge period.
The Under Voltage Lockout (UVLO) function ensures the
SG384xG’s supply voltage Vcc will be sufficiently high
before the output stage is enabled. The turn-on and
turn-off threshold voltages are fixed internally at
16V/10V for the SG3842G and at 8.9V/8.1V for the
SG3843G. The hysteresis voltage between turn-on and
turn-off prevents Vcc from being unstable during power
on/off sequencing. At start-up, before the output switch is
enabled, the Vcc hold-up capacitor CIN must be charged
up to 16V (SG3842G) through the start-up resistor RIN,
The ultra-small start-up current of 5uA allows very large
resistance values for the resistor RIN to be used, even with
low input voltages. For example, if VAC = 90Vrms, RIN
can be as large as 1.5 MΩ and still charge the hold-up
capacitor CIN. The power dissipation from this larger
resistance RIN would then be less than 70mW (0.07W),
even under high line conditions (VAC = 240Vrms). After
1.72
f (kHz) =
[
RT (kΩ)×CT (µF)]
Error Amplifier
The error amplifier’s inverting input is connected to the
FB pin, and the output is connected to the COMP pin. The
COMP output is available for external compensation,
allowing designers to control the feedback-loop
frequency-response. Non-inverting input is not wired out
© System General Corp.
- 12 -
www.sg.com.tw
Jun.28,2004
Version 1.4 ( IRO33.0007.B3)
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
the IC starts-up and begins normal operation, one of the
transformer’s auxiliary windings generates the supply
voltage Vcc, which supplies the operating current of the
SG384xG controller.
There are two factors that determine the PWM frequency:
1. The resistor RT and the capacitor CT determine the
RC charge and discharge times, and therefore, the
circuit frequency. They are both connected to the pin
RT/CT.
Slew Rate Controlled Output Driver
2. Internal comparator threshold voltages. Under
normal-load conditions, the internal comparator
threshold voltages are fixed at 1.3V (Vcomp,L) and
2.9V (Vcomp,H). Under light-load conditions, the
The BiCMOS output stage directly drives the external
power MOSFET up to the full supply voltage. The output
driver, with a low ON-resistance and high current-driving
capability, can easily drive an external capacitive load
larger than 1000pF. If operating under recommended
conditions, the switching frequency can go up to 500kHz.
Vcomp,H internal threshold voltage gradually increases.
This will increase the RC charging/discharging time,
therefore decreasing the frequency. Under ultra-light
or zero-load conditions, the Vcomp,H voltage is
increased to 4.6V. This will put the circuit into the
The output stage is designed to ensure zero cross-
conduction current. This minimizes heat dissipation,
increases efficiency, and enhances reliability. The output
driver is also slew-rate controlled to minimize EMI.
Oscillator Frequency (Fosc) vs COMP Voltage
VCC=15V
60
50
40
30
20
10
0
Temperature=25℃
Green-Mode: Linearly Decreasing
Frequency and Burst-Mode
System General’s patented Green-mode function reduces
the switching frequency under light-load and zero-load
conditions. Modulation of the PWM frequency can reduce
power consumption under light-load and zero-load
conditions, because the power loss is directly proportional
to the switching frequency.
1
1.5
2
2.5
3
COMP VOLTAGE (V)
lowest frequency it can operate at. Assuming RT =
10k and CT = 3.3nF, this is about 12kHz. The
frequency vs. COMP voltage (feedback from the
output load) is shown in Fig.1.
Most of the power loss in a power supply occurs due to the
switching loss of the transistor, the core loss of the
transformer and inductors, and the power loss of the
snubber. These sources of power loss all lose power in
proportion to the switching frequency.
Fig.1 Oscillator Frequency vs. COMP Voltage
The controller uses the output of the error amplifier as a
feedback voltage to calculate load conditions. When the
feedback voltage goes below the Green-mode threshold
voltage, the switching frequency will be reduced. Under
normal-load and high-load conditions, the PWM operates
as usual, and the frequency modulation feature does not
affect its operation.
If 12kHz is not low enough to meet stand-by power
conservation requirements, a shunt resistor RC can be
connected in parallel with the capacitor CT between
RT/CT and GND. This will allow the SG384xG to enter
into burst-mode.
For example, assuming RT = 10kΩ and RC = 47kΩ, the
peak RT/CT voltage would only be:
47
10 + 47
5V ×
= 4.12V
(
)
© System General Corp.
- 13 -
www.sg.com.tw
Jun.28,2004
Version 1.4 ( IRO33.0007.B3)
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
Since 4.12V is less than the internal Vcomp,H 4.6V voltage
under light-load conditions, the RT/CT oscillator would
take a long time to charge up to 4.6V. In this situation, the
RT/CT oscillator will stop oscillating.
Vcc Over Voltage Protection (OVP)
When the SG384xG’s supply voltage increases to 27V
due to abnormal conditions, such as an open loop from the
photo-coupler, or a short circuit on the output side, the
SG384xG will stop PWM output, to protect the entire
power supply from being damaged.
When oscillation stops, there is no PWM output.
Consequently, the energy required to supply the
SG384xG from the auxiliary winding also gets cut off.
This causes the supply voltage Vcc to start dropping. If
the supply voltage Vcc drops below the UVLO voltage, it
will take the SG384xG several hundred milliseconds to
start-up. This delay will cause too much fluctuation to the
output voltage. To avoid this, the SG384xG will
automatically reduce the internal Vcomp,H voltage, turning
the RT/CT oscillator back on when the Vcc supply
voltage falls within 1.5V of the UVLO voltage. In
Burst-mode, the PWM frequency is burst between 0Hz
and the light-load tens of kHz region, not over the full
frequency range. Fig.2 shows the Green-mode frequency
vs. the supply voltage Vcc. The Green-mode frequency is
fixed at 12kHz when Vcc is above 11V. When Vcc is
below 11V and approaching UVLO, the PWM frequency
is gradually increased. This increases the energy supplied
to Vcc, and pulls up the Vcc supply voltage to prevent it
from dropping below UVLO.
Noise Immunity
Noise from the current-sense or the control signal can
cause significant pulse-width jitter, particularly under
continuous-mode operation. Slope compensation partially
alleviates this problem, but the designer should be aware
of its presence.
The 384x has a single ground pin. High sink current in the
output therefore cannot be returned separately. Ceramic
bypass capacitors (0.1uF) from Vcc and VREF to ground
will provide low-impedance paths for high-frequency
transients.
For best results, good high-frequency and RF layout
practices should be followed. The designer should avoid
long PCB traces and component leads. The oscillator,
compensation, and filter components should be located
near the 384x. In order to minimize noise interference to
the oscillator, it is recommended that CT should never be
less than 1000pF.
These techniques help achieve optimal power savings.
The SG384xG can linearly decrease the PWM frequency
under light-load conditions, and enter into burst-mode
under ultra-light load and zero-load conditions. Linear
frequency reduction and burst-mode enable the SG384xG
to deliver excellent power savings and load regulation.
Noise caused by the output (pin 6) also causes problems
sometimes. This is because the pin is being pulled below
ground at turn-off by the external parasitic. This is
particularly true when driving a MOSFET. A resistor
series connected from the output (pin 6) to the gate of the
MOSFET will prevent such output noise.
Fosc-G (Green mode) vs Vcc
50
COMP=1.4V
40
30
20
10
0
Temperature=25℃
Drop below UVLO
9
10
11
12
13
14
Vcc VOLTAGE (V)
Fig.2 Green-mode Frequency vs. Supply Voltage Vcc
© System General Corp.
- 14 -
www.sg.com.tw
Jun.28,2004
Version 1.4 ( IRO33.0007.B3)
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
© System General Corp.
- 15 -
www.sg.com.tw
Jun.28,2004
Version 1.4 ( IRO33.0007.B3)
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
REFERENCE CIRCUIT
Universal Input, 12V/5A DC Output
P1
Vin
BD1
R1
L
3
1
4
2
4
1
VZ1
XC1
Q1
L2
R2
C1
1
3
C01
+
C2
C4
1,2
8,9
2
1
2
R3
Vo+
R4
1,2
8,9
TR2
D1
C3
R5
P2
F1
D2
1
2
D3
C5
+
3
4
C6
3
4
+
Vb
R6
D4
1
2
R7
5
6,7
R8
Q2
5
6,7
1
R9
R10
C7
R12
1
R11
U1
IS
SG3842G
3
R14
R13
C8
COM
VR
R16
D5
1
2
Vb
C10
C11
+
DO7
C12
VR
U2
4
3
1
2
C13
R18
U3
R17
R19
1
Vo+
R20
BOM
Symbol
BD1
C1
Components
Symbol
R1,3
R2
Components
BD 1A/600V
470K 1/4W
C2
EC 68u/400V
CC 102P/1KV
YC 222P
EC 1200u/16V
EC 680u/16V
EC 10u/25V
LED
R4
1M 1/4W
43 1/2W
4.7K 1/4W
0.5 1W
10 1/8W
100 1/8W
SCK054
EI28
C3
R5
R6
C4
C5
R13
R14
R17
TR2
T1
C6
C12
D1
D2
D3
ZD 15V
1N4148
2A/250V
UU10.5
U1
SG384xG
4N35D
D4
U2
F1
U3
TL431
L1
VZ1
XC1
VZ
L2
XC 0.22u
Q2
MOS 2A/600V
© System General Corp.
- 16 -
www.sg.com.tw
Jun.28,2004
Version 1.4 ( IRO33.0007.B3)
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
PACKAGE INFORMATION
8 DIP Outline Dimensions
D
Θ
8
1
5
4
e
B
E
L
b1
b
e
Dimensions
Millimeter
Min.
Inch
Min.
Symbol
Typ.
Max.
5.334
Typ.
Max.
0.210
A
A1
A2
b
b1
D
E
E1
e
L
eB
θ˚
0.381
3.175
0.015
0.125
3.302
1.524
0.457
9.271
7.620
6.350
2.540
3.302
9.017
7˚
3.429
0.130
0.060
0.018
0.365
0.300
0.250
0.100
0.130
0.355
7˚
0.135
9.017
6.223
10.160
6.477
0.355
0.245
0.400
0.255
2.921
8.509
0˚
3.810
9.525
15˚
0.115
0.335
0˚
0.150
0.375
15˚
© System General Corp.
Version 1.4 ( IRO33.0007.B3)
- 17 -
www.sg.com.tw
Jun.28,2004
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
8 SOP Outline Dimensions
C
8
5
H
E
F
1
4
b
e
D
Θ
L
A
A1
Dimensions
Millimeter
Min.
Inch
Min.
Symbol
Typ.
Max.
Typ.
Max.
A
A1
b
1.346
0.101
1.752
0.254
0.053
0.004
0.069
0.010
0.406
0.016
c
D
E
0.203
0.008
4.648
0.381
4.978
3.987
0.183
0.150
0.196
0.157
e
1.270
0.050
F
H
L
0.381X45˚
0.015X45˚
5.791
0.406
0˚
6.197
1.270
8˚
0.228
0.016
0˚
0.244
0.050
8˚
θ˚
© System General Corp.
Version 1.4 ( IRO33.0007.B3)
- 18 -
www.sg.com.tw
Jun.28,2004
Product Specification
BiCMOS Green-Mode PWM Controllers
SG3842G/ SG3843G
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 in other applications in
which failure of the 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.
- 19 -
www.sg.com.tw
Jun.28,2004
Version 1.4 ( IRO33.0007.B3)
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