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Product Specification Highly Integrated Green-Mode PWM Controller
SG6742
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 90VAC to 264VAC. 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 VDD drops below the UVLO lower limit when the controller starts up again. As long as VDD exceeds about 26V, the internal OVP circuit is triggered. SG6742 is available in an 8-pin DIP or SOP package.
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) VDD under-voltage lockout (UVLO) VDD 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 flyback power converters, including: Power Adapters Open-Frame SMPS supplies and
DESCRIPTION
The highly integrated SG6742 series of PWM controllers provides several features to enhance the performance of flyback converters.
TYPICAL APPLICATION
(c) System General Corp. Version 1.0.1 (IAO33.0083.B0)
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6742 PIN CONFIGURATION
MARKING INFORMATION
T: D = DIP, S = SOP P: Z =Lead Free Null=regular package XXXXXXXX: Wafer Lot Y: Year; WW: Week V: Assembly Location
GND FB NC HV
GATE VDD SENSE RT
SG6742TP
XXXXXXXXYWWV
ORDERING INFORMATION
Part Number
SG6742SZ SG6742DZ (Preliminary)
PWM Frequency Pb-Free Package
65KHz 65KHz SOP-8 DIP-8
PIN DESCRIPTIONS
Pin No.
1 2 3 4 5
Symbol
GND FB NC HV RT
Function
Ground Feedback NA Start-up Input Temperature Detection Current Sense Power Supply Driver Output
Description
Ground. 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. NC pin. For start-up, this pin is pulled high to the line input or bulk capacitor via resistors. 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. Current sense. The sensed voltage is used for peak-current-mode control and cycle-by-cycle current limiting. Power supply. The internal protection circuit disables PWM output as long as VDD exceeds the OVP trigger point. The totem-pole output driver. Soft driving waveform is implemented for improved EMI.
6 7 8
SENSE VDD GATE
(c) System General Corp. Version 1.0.1 (IAO33.0083.B0)
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6742
BLOCK DIAGRAM
(c) System General Corp. Version 1.0.1 (IAO33.0083.B0)
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6742
ABSOLUTE MAXIMUM RATINGS
Symbol
VDD VHV VL PD R JA TJ TSTG TL ESD
Parameter
Supply Voltage Input Voltage to HV Pin Input Voltage to FB, SENSE, CS Pin Power Dissipation TA < 50C Thermal Resistance (Junction-to-Air Operating Junction Temperature Storage Temperature Range Lead Temperature (Wave Soldering or Infrared, 10 Seconds) Electrostatic Discharge Capability, Human Body Model All pins except HV pin Electrostatic Discharge Capability, Machine Model All pins except HV pin
Value
30 500 -0.3 to 7.0 DIP SOP DIP SOP -40 to +125 -55 to +150 260 4 400 800 400 82.5 141.0
Unit
V V V mW C/W C C C KV 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
VDD 15V; TA 25C, unless otherwise noted.
VDD Section
Symbol
VDD-OP VDD-ON VDD-OFF IDD-ST IDD-OP IDD-OLP VTH-OLP VDD-OVP tD-VDDOVP
Parameter
Continuously Operating Voltage Start Threshold Voltage Minimum Operating Voltage Start-up Current Operating Supply Current Internal Sink Current IDD-OLP Off Voltage VDD Over-Voltage Protection VDD Over-Voltage Protection Debounce Time
Test Condition
Min.
15.5 9.5
Typ.
16.5 10.5
Max.
22 17.5 11.5 30
Unit
V V V A mA A V V s
VDD-ON - 0.16V VDD = 15V, GATE open VTH-OLP+0.1V 50 6.5 25 75 4 70 7.5 26 125
5 90 8.0 27 200
HV Section
Symbol
IHV IHV-LC
Parameter
Supply Current Drawn from HV Pin Leakage Current After Start-up
Test Condition
VAC=90V (VDC=120V) VDD=10F HV = 500V, VDD = VDD-OFF+1V
Min.
Typ.
1.2 1
Max.
Unit
mA
20
A
(c) System General Corp. Version 1.0.1 (IAO33.0083.B0)
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6742
Oscillator Section
Symbol
FOSC tHOP FOSC-G FDV FDT
Parameter
Frequency in Nominal Mode Hopping Period Green-Mode Frequency Frequency Variation vs. VDD Deviation Frequency Variation vs. Temp. Deviation
Test Condition
Center Frequency Hopping Range
Min.
62 3.7 18
Typ.
65 4.2 4.4 22
Max.
68 4.7 25 5 5
Unit
KHz ms KHz % %
VDD=11V to 22V TA=-20 to 85C
* Hopping off at green-mode.
Feedback Input Section
Symbol
AV ZFB VFB-OPEN VFB-OLP tD-OLP VFB-N VFB-G
Parameter
Input Voltage to Current-Sense Attenuation Input Impedance Output High Voltage FB Open-Loop Trigger Level Delay Time of FB Pin Open Loop Protection Green-Mode Entry FB Voltage Green-Mode Ending FB Voltage
Test Condition
Min.
1/4.5 4
Typ.
1/4.0
Max.
1/3.5 7
Unit
V/V k V V ms V V
FB pin open
5.5 5.0 53 1.9 5.2 56 2.1 VFB-N-0.5 5.4 59 2.3
PWM Frequency
FOSC
FOSC-G
VFB-G
VFB-N
VFB
(c) System General Corp. Version 1.0.1 (IAO33.0083.B0)
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6742
Current-Sense Section
Symbol
ZSENSE VSTHFL VSTHVA tPD tLEB VS-SCP tD-SSCP
Parameter
Input Impedance Current Limit Flatten Threshold Voltage Current Limit Valley Threshold Voltage Delay to Output Leading-Edge Blanking Time Threshold Voltage for SENSE Short-circuit Protection Delay Time for SENSE Short-circuit Protection
Test Condition
Min.
0.87
Typ.
12 0.90 0.22 100 350 0.15 150
Max.
0.93 0.26 200 425 0.20 200
Unit
K V V ns ns V s
VSTHFL-VSTHVA
0.18 275 0.10
VSENSE < 0.15V
100
GATE Section
Symbol
DCYMAX VGATE-L VGATE-H tr tf IGATE-SOURCE VGATE-CLAMP
Parameter
Maximum Duty Cycle Gate Low Voltage Gate High Voltage Gate Rising Time Gate Falling Time Gate Source Current Gate Output Clamping Voltage
Test Condition
VDD=15V, IO=50mA VDD=12V, IO=50mA VDD=15V, CL=1nF VDD=15V, CL=1nF VDD=15V, GATE=6V VDD=22V
Min.
60 8 150 30 250
Typ.
65
Max.
70 1.5
Unit
% V V ns ns mA V
250 50
350 90 18
RT Section
Symbol
IRT VRTTH1 VRTTH2 tD-OTP1 tD-OTP2
Parameter
Output Current from the RT Pin Over-Temperature Protection Threshold Voltage Over-Temperature Protection Threshold Voltage Over-Temperature Latch-off Debounce Over-Temperature Latch-off Debounce
Test Condition
Min.
92
Typ.
100 1.050 0.70 12 100
Max.
108 1.085 0.75 16 140
Unit
A V V ms s
0.7V VRT 1.05V, after 1.015 12ms latch off VRT 0.7V, after 100s latch off VRTTH2 VRT VRTTH1 VRT < VRTTH2 0.65 8 60
Over Temperature Protection (OTP)
Symbol
TOTP TRestart *
Parameter
Protection Junction Temperature* Restart Junction Temperature**
Test Condition
Min.
Typ.
135 TOTP -25
Max.
Unit
C 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.
(c) System General Corp. Version 1.0.1 (IAO33.0083.B0)
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6742
TYPICAL CHARACTERISTICS
Start-up Current (IDD-ST) vs Temperature
25 20 5 4
Operating Supply Current (IDD-OP) vs Temperature
IDD_ST (uA)
IDD-OP (mA)
15 10 5 0 -40
3 2 1 0 -40
-30
-15
0
25
50
75
85
100
125
-30
-15
0
25
50
75
85
100
125
Temperature ()
Temperature ()
Start Threshold Voltage (VDD-ON) vs Temperature)
20 19 18 17 16 15 -40 13 12
Minimum Operating Voltage (V DD-OFF) vs Temperature
VDD-OFF (V)
-30 -15 0 25 50 75 85 100 125
VDD-ON (V)
11 10 9 8 -40
-30
-15
0
25
50
75
85
100
125
Temperature ()
Temperature ()
Supply current drawn from pin HV (IHV) vs Temperature
5 4 10 8
HV pin Leakage Current after Start-up (IHV-LC) vs Temperature
IHV (mA)
3 2 1 0 -40
IHV-LC (uA)
-30 -15 0 25 50 75 85 100 125
6 4 2 0 -40
-30
-15
0
25
50
75
85
100
125
Temperature ()
Temperature ()
(c) System General Corp. Version 1.0.1 (IAO33.0083.B0)
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6742
Frequency in nominal mode (FOSC) vs Temperature
70 68 66 64 62 60 -40 70 68
Maximum Duty Cycle (DCYMAX) vs Temperature
DCYMAX (%)
-30 -15 0 25 50 75 85 100 125
FOSC (kHz)
66 64 62 60 -40
-30
-15
0
25
50
75
85
100
125
Temperature ()
Temperature ()
Output Current from the RT pin (IRT) vs Temperature
104 102 100 98 96 94 -40
IRT (uA)
-30
-15
0
25
50
75
85
100
125
Temperature ()
(c) System General Corp. Version 1.0.1 (IAO33.0083.B0)
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6742
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 RHV, which are recommended as 1N4007 and 100K. 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 VDD capacitor level reaches VDD-ON, the start-up current switches off. At this moment, the VDD capacitor only supplies the SG6742 to keep the VDD before the auxiliary winding of the main transformer to carry on provide the operating current.
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 VDD before the energy can be delivered from auxiliary winding of the main transformer. VDD must not drop below 10.5V during this start-up process. This UVLO hysteresis window ensures that hold-up capacitor is adequate to supply VDD 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.
Operating Current
Operating current is around 4mA. The low operating current enables better efficiency and reduces the requirement of VDD hold-up capacitance.
Green-Mode Operation
The patented 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. VFB, which is derived from the voltage feedback loop, is taken as the reference. Once VFB is lower than the threshold voltage, switching frequency is continuously decreased to the minimum green mode frequency, around 22KHz.
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.
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 VFB, the feedback voltage. When the voltage on the SENSE pin reaches around VCOMP = (VFB-1.2)/4, a switch cycle is terminated immediately. VCOMP is internally clamped to a variable voltage around 0.85V for output power limit.
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, tPD. This delay introduces additional current, proportional to tPD*VIN / LP. Since the delay is nearly constant, regardless of the input voltage VIN, 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.
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. (c) System General Corp. Version 1.0.1 (IAO33.0083.B0)
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6742
When VDD goes below the turn-off threshold (eg, 10.5V) the controller is totally shut down. VDD 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.
VDD Over-Voltage Protection
VDD over-voltage protection has been built in to prevent damage due to abnormal conditions. Once the VDD voltage is over the over-voltage protection voltage (VDD-OVP) and lasts for tD-VDDOVP, the PWM pulses are be disabled until the VDD voltage drops below the UVLO, then start-up again. Over-voltage conditions are usually caused by open feedback loops.
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.
Thermal Protection
An NTC thermistor RNTC in series with a resistor RA can be connected from pin RT to ground. A constant current IRT is output from pin RT. The voltage on RT pin can be expressed as VRT = IRT x (RNTC + Ra), in which IRT = 2 x (1.3V / RI). At high ambient temperature, RNTC is smaller, such that VRT decreases. When VRT is less than 1.05V (VRTTH1), the PWM is turned off after 12ms (tD-OTP1). If VRT is less than 0.7V (VRTTH2), PWM should be turned off immediately after 100s (tD-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 tD-OLP, PWM output is turned off. As PWM output is turned off, the supply voltage VDD begins decreasing.
(c) System General Corp. Version 1.0.1 (IAO33.0083.B0)
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6742
REFERENCE CIRCUIT (12V/5A)
F1 CN1 1 2 3 1 3 CN1 L1 T1 2 4 2 4 C1 VZ1 C2 1 3 4 1 2 4 5 6 2 1 2 R2 1 T2 8 3 + 3 2 C3 D4 C5 C4 2 + C7 1 3 7 1 R1 Q1 1 L2 VO+ 2 2 L3 2 + C8 1 3 4 1 VO+ 2 C6
BD1
1
D1
1
D2
2
VO2
R3 2 R4 1 3 1 2 U1 1 2 C12 3 4 GND FB NC HV SG6742 GATE VDD SENSE RT 8 7 6 5 R6 C10 1 + C9 D3 2 R5 R7 THER1 U2 R8 4 1 Q2
VO+
R9 3 K2 C11 R
R10
U3 A
R11
BOM
Reference
BD1 C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 D1 D2 D3 D4 F1 L1 L2 L3
Component
BD 4A/600V XC 0.68F/300V XC 0.1F/300V YC 222pF/Y1 EC 120F/400V CC 0.01F/500V CC 102pF/100V EC 1000F/25V EC 470F/25V EC 22F/50V CC 470pF/50V CC 222pF/50V CC 103pF/50V Zener Diode 15V 1/2W (option) BYV95C FR103 1N4007 FUSE 4A/250V Inductor (900H) Inductor (2H) Inductor (900H)
Reference
Q1 Q2 R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 THER1 T1 T2 U1 U2 U3 VZ1
Component
STP20-100CT MOS 7A/600V R 100Kohm 1/2W R 47ohm 1/4W R 100Kohm 1/2W R 20ohm 1/8W R 100ohm 1/8W R 4.7Kohm 1/8W R 0.3ohm 2W R 680ohm 1/8W R 4.7Kohm 1/8W R 150Kohm 1/8W R 39Kohm 1/8W Thermistor TTC104 10mH 600H(PQ2620) IC SG6742 IC PC817 IC TL431 VZ 9G
(c) System General Corp. Version 1.0.1 (IAO33.0083.B0)
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6742
PACKAGE INFORMATION 8PINS-DIP(D)
D
8 5
X
E1
E
eB
1
4
A1
A2
L b1 b e
Dimensions
Millimeters Min. Typ.
0.381 3.175 3.302 1.524 0.457 9.017 6.223 2.921 8.509 0 9.271 7.620 6.350 2.540 3.302 9.017 7 3.810 9.525 15 0.115 0.335 0 6.477 0.245 10.160 0.355 3.429
A
Symbol
A A1 A2 b b1 D E E1 e L eB
Max.
5.334
Inches Min.
0.015 0.125
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
(c) System General Corp. Version 1.0.1 (IAO33.0083.B0)
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6742
8PINS-SOP(S)
C
8
5
1 b
4 e
D
A1
A
Dimensions
Symbol
A A1 b c D E e F H L
Millimeter Min. Typ.
1.346 0.101 0.406 0.203 4.648 3.810 1.016 5.791 0.406 0
1.270 0.381X45
(c) System General Corp. Version 1.0.1 (IAO33.0083.B0)
H F
E
L
Max.
1.752 0.254
Inch Min.
0.053 0.004
Typ.
0.016 0.008
Max.
0.069 0.010
4.978 3.987 1.524 6.197 1.270 8
0.183 0.150 0.040 0.228 0.016 0
0.050 0.015X45
0.196 0.157 0.060 0.244 0.050 8
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6742
(c) System General Corp. Version 1.0.1 (IAO33.0083.B0)
- 14 -
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