Product Specification
Highly Integrated Green-Mode PWM Controller
SG6742
© System General Corp. - 1 - www.sg.com.tw • www.fairchildsemi.com
Version 1.0.2 (IAO33.0083.B0) June 14, 2011
FEATURES
High-voltage start-up
Low operating current (4mA)
Linearly decreasing PWM frequency to 22KHz
Frequency jittering to reduce EMI emission
Fixed PWM frequency (65KHz)
Peak-current-mode control
Cycle-by-cycle current limiting
Leading-edge blanking
Synchronized slope compensation
Internal open-loop protection
GATE output maximum voltage clamp (18V)
V
DD
under-voltage lockout (UVLO)
V
DD
over voltage protection (OVP)
Programmable over-temperature protection (RT)
Internal latch circuit (OVP, RT)
Constant power limit (full AC input range)
Internal OTP sensor with hysteresis
APPLICATIONS
General-purpose switch-mode power supplies and
flyback power converters, including:
Power Adapters
Open-Frame SMPS
DESCRIPTION
The highly integrated SG6742 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
linearly decrease the switching frequency at light-load
conditions. To avoid acoustic noise problems, the
minimum PWM frequency is set above 22KHz. This
green-mode function enables the power supply to meet
international power conservation requirements. With the
internal high-voltage start-up circuitry, the power loss due
to bleeding resistors is eliminated. To further reduce power
consumption, SG6742 is manufactured using the BiCMOS
process, which allows an operating current of 4mA.
SG6742 integrates a frequency a hopping function that
helps reduce EMI emission of a power supply with
minimum line filters. Also, its built-in synchronized slope
compensation achieves stable peak-current-mode control.
The proprietary internal line compensation ensures
constant output power limit over a wide AC input voltages,
from 90V
AC
to 264V
AC
.
SG6742 provides many protection functions. In addition
to cycle-by-cycle current limiting, the internal open-loop
protection circuit ensures safety should an open-loop or
output short-circuit failure occur. PWM output is disabled
until V
DD
drops below the UVLO lower limit when the
controller starts up again. As long as V
DD
exceeds about
26V, the internal OVP circuit is triggered.
SG6742 is available in an 8-pin DIP or SOP package.
TYPICAL APPLICATION
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6742
© System General Corp. - 2 - www.sg.com.tw • www.fairchildsemi.com
Version 1.0.2 (IAO33.0083.B0) June 14, 2011
MARKING INFORMATION PIN CONFIGURATION
ORDERING INFORMATION
Part Number PWM Frequency
Pb-Free Package
SG6742SZ 65KHz
SOP-8
SG6742DZ (Preliminary) 65KHz
DIP-8
PIN DESCRIPTIONS
Pin No. Symbol Function Description
1 GND Ground Ground.
2 FB Feedback The signal from the external compensation circuit is fed into this pin. The PWM duty cycle is
determined in response to the signal on this pin and the current-sense signal on SENSE pin.
3 NC NA NC pin.
4 HV Start-up Input For start-up, this pin is pulled high to the line input or bulk capacitor via resistors.
5 RT Temperature
Detection
For over-temperature protection, an external
NTC thermistor is connected from this pin to GND
pin. The impedance of the NTC decreases at high temperatures. Once the voltage of the RT
pin drops below a fixed limit, PWM output is disabled.
6 SENSE Current Sense Current sense. The sensed voltage is used for peak-current-mode control and cycle-by-cycle
current limiting.
7 VDD Power Supply Power supply. The internal protection circuit disables PWM output as long as V
DD
exceeds the
OVP trigger point.
8 GATE Driver Output The totem-pole output driver. Soft driving waveform is implemented for improved EMI.
HV
NC
GATE
VDD
SENSE
RT
FB
T: D = DIP, S = SOP
P: Z =Lead Free
Null=regular package
XXXXXXXX: Wafer Lot
Y: Year; WW: Week
V: Assembly Location
SG6742TP
XXXXXXXXYWWV
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6742
© System General Corp. - 3 - www.sg.com.tw • www.fairchildsemi.com
Version 1.0.2 (IAO33.0083.B0) June 14, 2011
BLOCK DIAGRAM
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6742
© System General Corp. - 4 - www.sg.com.tw • www.fairchildsemi.com
Version 1.0.2 (IAO33.0083.B0) June 14, 2011
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Value Unit
V
DD
Supply Voltage 30 V
V
HV
Input Voltage to HV Pin 500 V
V
L
Input Voltage to FB, SENSE, CS Pin -0.3 to 7.0 V
P
D
Power Dissipation T
A
< 50°C DIP 800 mW
SOP 400
R
ΘJA
Thermal Resistance (Junction-to-Air） DIP 82.5 °C/W
SOP 141.0
T
J
Operating Junction Temperature -40 to +125 °C
T
STG
Storage Temperature Range -55 to +150 °C
T
L
Lead Temperature (Wave Soldering or Infrared, 10 Seconds) 260 °C
ESD Electrostatic Discharge Capability, Human Body Model All pins except HV pin 4 KV
Electrostatic Discharge Capability, Machine Model All pins except HV pin 400 V
* All voltage values, except differential voltages, are given with respect to the GND pin.
* Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device.
ELECTRICAL CHARACTERISTICS
V
DD
＝ 15V; T
A
＝ 25°C, unless otherwise noted.
V
DD
Section
Symbol Parameter Test Condition Min. Typ. Max. Unit
V
DD-OP
Continuously Operating Voltage 22 V
V
DD-ON
Start Threshold Voltage 15.5 16.5 17.5 V
V
DD-OFF
Minimum Operating Voltage 9.5 10.5 11.5 V
I
DD-ST
Start-up Current V
DD-ON
– 0.16V 30 µA
I
DD-OP
Operating Supply Current V
DD
= 15V, GATE open 4 5 mA
I
DD-OLP
Internal Sink Current V
TH-OLP
+0.1V 50 70 90 µA
V
TH-OLP
I
DD-OLP
Off Voltage 6.5 7.5 8.0 V
V
DD-OVP
V
DD
Over-Voltage Protection 25 26 27 V
t
D-VDDOVP
V
DD
Over-Voltage Protection Debounce Time
75 125 200 µs
HV Section
Symbol Parameter Test Condition Min. Typ. Max. Unit
I
HV
Supply Current Drawn from HV Pin V
AC
=90V (V
DC
=120V)；
V
DD
=10µF 1.2 mA
I
HV-LC
Leakage Current After Start-up HV = 500V,
V
DD
= V
DD-OFF
+1V 1 20 µA
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6742
© System General Corp. - 5 - www.sg.com.tw • www.fairchildsemi.com
Version 1.0.2 (IAO33.0083.B0) June 14, 2011
Oscillator Section
Symbol Parameter Test Condition Min. Typ. Max. Unit
F
OSC
Frequency in Nominal Mode Center Frequency 62 65 68 KHz
Hopping Range ±3.7 ±4.2 ±4.7
t
HOP
Hopping Period 4.4 ms
F
OSC-G
Green-Mode Frequency 18 22 25 KHz
F
DV
Frequency Variation vs. V
DD
Deviation V
DD
=11V to 22V 5 %
F
DT
Frequency Variation vs. Temp. Deviation T
A
=-20 to 85°C 5 %
* Hopping off at green-mode.
Feedback Input Section
Symbol Parameter Test Condition Min. Typ. Max. Unit
A
V
Input Voltage to Current-Sense Attenuation 1/4.5 1/4.0 1/3.5 V/V
Z
FB
Input Impedance 4 7 kΩ
V
FB-OPEN
Output High Voltage FB pin open 5.5 V
V
FB-OLP
FB Open-Loop Trigger Level
5.0 5.2 5.4 V
t
D-OLP
Delay Time of FB Pin Open Loop Protection 53 56 59 ms
V
FB-N
Green-Mode Entry FB Voltage 1.9 2.1 2.3 V
V
FB-G
Green-Mode Ending FB Voltage V
FB-N
-0.5 V
PWM Frequency
F
OSC
F
OSC-G
V
FB
V
FB-N
V
FB-G
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6742
© System General Corp. - 6 - www.sg.com.tw • www.fairchildsemi.com
Version 1.0.2 (IAO33.0083.B0) June 14, 2011
Current-Sense Section
Symbol Parameter Test Condition Min. Typ. Max. Unit
Z
SENSE
Input Impedance 12 KΩ
V
STHFL
Current Limit Flatten Threshold Voltage 0.87 0.90 0.93 V
V
STHVA
Current Limit Valley Threshold Voltage V
STHFL
–V
STHVA
0.18 0.22 0.26 V
t
PD
Delay to Output 100 200 ns
t
LEB
Leading-Edge Blanking Time 275 350 425 ns
V
S-SCP
Threshold Voltage for SENSE Short-circuit
Protection 0.10 0.15 0.20 V
t
D-SSCP
Delay Time for SENSE Short-circuit
Protection V
SENSE
< 0.15V 100 150 200 µs
GATE Section
Symbol Parameter Test Condition Min. Typ. Max. Unit
DCY
MAX
Maximum Duty Cycle 60 65 70 %
V
GATE-L
Gate Low Voltage V
DD
=15V, I
O
=50mA 1.5 V
V
GATE-H
Gate High Voltage V
DD
=12V, I
O
=50mA 8 V
tr Gate Rising Time V
DD
=15V, C
L
=1nF 150 250 350 ns
tf Gate Falling Time V
DD
=15V, C
L
=1nF 30 50 90 ns
I
GATE-SOURCE
Gate Source Current V
DD
=15V, GATE=6V 250 mA
V
GATE-CLAMP
Gate Output Clamping Voltage V
DD
=22V 18 V
RT Section
Symbol Parameter Test Condition Min. Typ. Max. Unit
I
RT
Output Current from the RT Pin 92 100 108 µA
V
RTTH1
Over-Temperature Protection Threshold
Voltage
0.7V ＜ V
RT
＜ 1.05V, after
12ms latch off 1.015 1.050 1.085 V
V
RTTH2
Over-Temperature Protection Threshold
Voltage
V
RT
＜ 0.7V, after 100µs
latch off 0.65 0.70 0.75 V
t
D-OTP1
Over-Temperature Latch-off Debounce V
RTTH2
＜ V
RT
＜ V
RTTH1
8 12 16 ms
t
D-OTP2
Over-Temperature Latch-off Debounce V
RT
< V
RTTH2
60 100 140 µs
Over Temperature Protection (OTP)
Symbol Parameter Test Condition Min. Typ. Max. Unit
T
OTP
Protection Junction Temperature
*
135 °C
T
Restart
Restart Junction Temperature
**
T
OTP
-25 °C
* When activated, the output is disabled and the latch is turned off.
** This is the threshold temperature for enabling the output again and resetting the latch after over-temperature protection has
been activated.
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6742
© System General Corp. - 7 - www.sg.com.tw • www.fairchildsemi.com
Version 1.0.2 (IAO33.0083.B0) June 14, 2011
TYPICAL CHARACTERISTICS
Start-up Current (I
DD-ST
) vs Temperature
0
5
10
15
20
25
-40 -30 -15 0 25 50 75 85 100 125
Temperature (℃
℃℃
℃)
I
DD_ST
(uA)
Operating Supply Current (I
DD-OP
) vs Temperature
0
1
2
3
4
5
-40 -30 -15 0 25 50 75 85 100 125
Temperature (℃
℃℃
℃)
I
DD-OP
(mA)
Start Threshold Voltage (V
DD-ON
) vs Temperature)
15
16
17
18
19
20
-40 -30 -15 0 25 50 75 85 100 125
Temperature (℃
℃℃
℃)
V
DD-ON
(V)
Minimum Operating Voltage (V
DD-OFF
) vs Temperature
8
9
10
11
12
13
-40 -30 -15 0 25 50 75 85 100 125
Temperature (℃
℃℃
℃)
V
DD-OFF
(V)
Supply current drawn from pin HV (I
HV
) vs Temperature
0
1
2
3
4
5
-40 -30 -15 0 25 50 75 85 100 125
Temperature (℃
℃℃
℃)
I
HV
(mA)
HV pin Leakage Current after Start-up (I
HV-LC
) vs Temperature
0
2
4
6
8
10
-40 -30 -15 0 25 50 75 85 100 125
Temperature (℃
℃℃
℃)
I
HV-LC
(uA)
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6742
© System General Corp. - 8 - www.sg.com.tw • www.fairchildsemi.com
Version 1.0.2 (IAO33.0083.B0) June 14, 2011
Frequency in nominal mode (F
OSC
) vs Temperature
60
62
64
66
68
70
-40 -30 -15 0 25 50 75 85 100 125
Temperature (℃
℃℃
℃)
F
OSC
(kHz)
Maximum Duty Cycle (DCY
MAX
) vs Temperature
60
62
64
66
68
70
-40 -30 -15 0 25 50 75 85 100 125
Temperature (℃
℃℃
℃)
DCY
MAX
(%)
Output Current from the RT pin (I
RT
) vs Temperature
94
96
98
100
102
104
-40 -30 -15 0 25 50 75 85 100 125
Temperature (℃
℃℃
℃)
I
RT
(uA)
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6742
© System General Corp. - 9 - www.sg.com.tw • www.fairchildsemi.com
Version 1.0.2 (IAO33.0083.B0) June 14, 2011
OPERATION DESCRIPTION
Start-up Current
For start-up, the HV pin is connected to the line input or
bulk capacitor through an external diode and resistor R
HV
,
which are recommended as 1N4007 and 100KΩ. Typical
start-up current drawn from the HV pin is 1.2mA and it
charges the hold-up capacitor through the diode and
resistor. When the V
DD
capacitor level reaches V
DD-ON
, the
start-up current switches off. At this moment, the V
DD
capacitor only supplies the SG6742 to keep the V
DD
before the auxiliary winding of the main transformer to
carry on provide the operating current.
Operating Current
Operating current is around 4mA. The low operating
current enables better efficiency and reduces the
requirement of V
DD
hold-up capacitance.
Green-Mode Operation
The proprietary green-mode function provides an off-time
modulation to reduce the switching frequency in
light-load and no-load conditions. The on-time is limited
for better abnormal or brownout protection. V
FB
, which is
derived from the voltage feedback loop, is taken as the
reference. Once V
FB
is lower than the threshold voltage,
switching frequency is continuously decreased to the
minimum green mode frequency, around 22KHz.
Current Sensing / PWM Current Limiting
Peak-current-mode control is utilized to regulate output
voltage and provide pulse-by-pulse current limiting. The
switch current is detected by a sense resistor into the
SENSE pin. The PWM duty cycle is determined by this
current sense signal and V
FB
, the feedback voltage. When
the voltage on the SENSE pin reaches around V
COMP
=
(V
FB
–1.2)/4, a switch cycle is terminated immediately.
V
COMP
is internally clamped to a variable voltage around
0.85V for output power limit.
Leading-Edge Blanking
Each time the power MOSFET is switched on, a turn-on
spike occurs on the sense-resistor. To avoid premature
termination of the switching pulse, a leading-edge
blanking time is built in. During this blanking period, the
current-limit comparator is disabled and it cannot switch
off the gate driver.
Under-Voltage Lockout (UVLO)
The turn-on and turn-off threshold are fixed internally at
16.5V/10.5V. During start-up, the hold-up capacitor must
be charged to 16.5V through the start-up resistor so that
IC is enabled. The hold-up capacitor continues to supply
V
DD
before the energy can be delivered from auxiliary
winding of the main transformer. V
DD
must not drop
below 10.5V during this start-up process. This UVLO
hysteresis window ensures that hold-up capacitor is
adequate to supply V
DD
during start-up.
Gate Output / Soft Driving
The SG6742 BiCMOS output stage is a fast totem pole
gate driver. Cross conduction is avoided to minimize heat
dissipation, increases efficiency, and enhances reliability.
The output driver is clamped by an internal 18V Zener
diode to protect power MOSFET transistors against
undesirable gate over voltage. A soft driving waveform is
implemented to minimize EMI.
Built-in Slope Compensation
The sensed voltage across the current-sense resistor is
used for peak-current-mode control and pulse-by-pulse
current limiting. Built-in slope compensation improves
stability or prevents sub-harmonic oscillation. SG6742
inserts a synchronized positive-going ramp at every
switching cycle.
Constant Output Power Limit
When the SENSE voltage, across the sense resistor Rs,
reaches the threshold voltage, around 0.9V, the output
GATE drive is turned off after a small delay, t
PD
. This
delay introduces additional current, proportional to
t
PD
•V
IN
/ L
P
. Since the delay is nearly constant, regardless
of the input voltage V
IN
, higher input voltage results in a
larger additional current and the output power limit is
higher than under low input line voltage. To compensate
this variation for wide AC input range, a sawtooth
power-limiter is designed to solve the unequal
power-limit problem. The power limiter is designed as a
positive ramp signal and is fed to the inverting input of the
OCP comparator. This results in a lower current limit at
high-line inputs than at low-line inputs.
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6742
© System General Corp. - 10 - www.sg.com.tw • www.fairchildsemi.com
Version 1.0.2 (IAO33.0083.B0) June 14, 2011
V
DD
Over-Voltage Protection
V
DD
over-voltage protection has been built in to prevent
damage due to abnormal conditions. Once the V
DD
voltage is over the over-voltage protection voltage
(V
DD-OVP
) and lasts for t
D-VDDOVP
, the PWM pulses are be
disabled until the V
DD
voltage drops below the UVLO,
then start-up again. Over-voltage conditions are usually
caused by open feedback loops.
Thermal Protection
An NTC thermistor R
NTC
in series with a resistor R
A
can
be connected from pin RT to ground. A constant current
I
RT
is output from pin RT. The voltage on RT pin can be
expressed as V
RT
= I
RT
× (R
NTC
+ Ra), in which I
RT
= 2 x
(1.3V / R
I
). At high ambient temperature, R
NTC
is smaller,
such that V
RT
decreases. When V
RT
is less than 1.05V
(V
RTTH1
), the PWM is turned off after 12ms (t
D-OTP1
). If
V
RT
is less than 0.7V (V
RTTH2
), PWM should be turned off
immediately after 100µs (t
D-OTP2
).
Limited Power Control
The FB voltage increases every time the output of the
power supply is shorted or over-loaded. If the FB voltage
remains higher than a built-in threshold for longer than
t
D-OLP
, PWM output is turned off. As PWM output is
turned off, the supply voltage V
DD
begins decreasing.
When V
DD
goes below the turn-off threshold (eg, 10.5V)
the controller is totally shut down. V
DD
is charged up to
the turn-on threshold voltage of 16V through the start-up
resistor until PWM output is restarted. This protection
feature is activated as long as the over-loading condition
persists. This prevents the power supply from overheating
due to over loading conditions.
Noise Immunity
Noise on the current sense or 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. Avoiding long PCB traces
and component leads, locating compensation and filter
components near the SG6742, and increasing the power
MOS gate resistance improves performance.
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6742
© System General Corp. - 11 - www.sg.com.tw • www.fairchildsemi.com
Version 1.0.2 (IAO33.0083.B0) June 14, 2011
REFERENCE CIRCUIT (12V/5A)
1
2
3
CN1
CN1
F1
C2
21
+
C4
2
1
3
4
BD1
2 1
D2
1
23
Q2
R7
GND
1
FB
2
NC
3
HV
4RT 5
SENSE 6
VDD 7
GATE 8
U1 SG6742
R4
12
43
U2
C6R2
1
3
2
Q1
21
+
C7
21
D3
R9
R11
R10
R8
C11
21
+
C9
VZ1
C1
1 2
3 4
T1
4
2
3 7
8
6
5
T2
VO+
VO-
C3
1 2
3 4
L1
21
+
C8
1 2
3 4
L3
2 1
D1
A K
R
U3
VO+
1 2
L2
R3
VO+
R1
C5
R6 C10
R5
C12
21
D4
THER1
BOM
Reference Component Reference Component
BD1 BD 4A/600V Q1 STP20-100CT
C1 XC 0.68µF/300V Q2 MOS 7A/600V
C2 XC 0.1µF/300V R1 R 100Kohm 1/2W
C3 YC 222pF/Y1 R2 R 47ohm 1/4W
C4 EC 120µF/400V R3 R 100Kohm 1/2W
C5 CC 0.01µF/500V R4 R 20ohm 1/8W
C6 CC 102pF/100V R5 R 100ohm 1/8W
C7 EC 1000µF/25V R6 R 4.7Kohm 1/8W
C8 EC 470µF/25V R7 R 0.3ohm 2W
C9 EC 22µF/50V R8 R 680ohm 1/8W
C10 CC 470pF/50V R9 R 4.7Kohm 1/8W
C11 CC 222pF/50V R10 R 150Kohm 1/8W
C12 CC 103pF/50V R11 R 39Kohm 1/8W
D1 Zener Diode 15V 1/2W (option) THER1 Thermistor TTC104
D2 BYV95C T1 10mH
D3 FR103 T2 600µH(PQ2620)
D4 1N4007 U1 IC SG6742
F1 FUSE 4A/250V U2 IC PC817
L1 Inductor (900µH) U3 IC TL431
L2 Inductor (2µH) VZ1 VZ 9G
L3 Inductor (900µH)
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6742
© System General Corp. - 12 - www.sg.com.tw • www.fairchildsemi.com
Version 1.0.2 (IAO33.0083.B0) June 14, 2011
PACKAGE INFORMATION
8PINS-DIP(D)
4
1
8 5
D
E1
E
e
B
A1
A2
A
b
b1
L
e
¢
X
Θ
Dimensions
Symbol Millimeters Inches
Min. Typ. Max. Min. Typ. Max.
A 5.334 0.210
A1 0.381 0.015
A2 3.175 3.302 3.429 0.125 0.130 0.135
b 1.524 0.060
b1 0.457 0.018
D 9.017 9.271 10.160 0.355 0.365 0.400
E 7.620 0.300
E1 6.223 6.350 6.477 0.245 0.250 0.255
e 2.540 0.100
L 2.921 3.302 3.810 0.115 0.130 0.150
eB 8.509 9.017 9.525 0.335 0.355 0.375
θ˚ 0˚ 7˚ 15˚ 0˚ 7˚ 15˚
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6742
© System General Corp. - 13 - www.sg.com.tw • www.fairchildsemi.com
Version 1.0.2 (IAO33.0083.B0) June 14, 2011
8PINS-SOP(S)
Θ
14
85
H
E
e
b
A
A1
D
C
F
L
Dimensions
Symbol
Millimeter
Inch
Min.
Typ.
Max.
Min.
Typ.
Max.
A
1.346
1.752
0.053
0.069
A1
0.101
0.254
0.004
0.010
b
0.406
0.016
c
0.203
0.008
D
4.648
4.978
0.183
0.196
E
3.810
3.987
0.150
0.157
e
1.016
1.270
1.524
0.040
0.050
0.060
F
0.381X45
˚
˚˚
˚
0.015X45
˚
˚˚
˚
H
5.791
6.197
0.228
0.244
L
0.406
1.270
0.016
0.050
θ
˚
0
˚
˚˚
˚
8
˚
˚˚
˚
0
˚
˚˚
˚
8
˚
˚˚
˚
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6742
© System General Corp. - 14 - www.sg.com.tw • www.fairchildsemi.com
Version 1.0.2 (IAO33.0083.B0) June 14, 2011