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Product Specification Highly-Integrated Green-Mode PWM Controller
SG6846
the switching frequency under light-load conditions. Under zero-load conditions, the power supply enters burst-mode. This completely shuts off PWM output. The output restarts just before the supply voltage drops below the UVLO lower limit. This green-mode function enables power supplies to easily meet international power conservation requirements. The SG6846 is especially designed for SMPS with surge-current output. It is incorporated with a two-level OCP function. Besides the cycle-by-cycle current limiting, if the switching current is higher than 2/3 of the peak-current threshold for a delay time, over-current protection will be activated such that the SG6846 will be totally shutdown. Other protection functions include: AC input brownout protection with hysteresis, and VDD over-voltage protection. For over-temperature protection, an external NTC thermistor can be applied to sense the ambient temperature. When OCP, VDD OVP, or OTP are activated, an internal latch circuit is used to latch-off the controller. The latch will reset when the VDD supply is removed. Other features of this controller include: Built-in synchronized slope compensation, proprietary internal compensation for constant output power limit over universal AC input range. Also, the gate output is clamped at 18V to protect the external MOSFET from over-voltage damage. The SG6846 series controllers are available in both 8-pin DIP and SO packages.
FEATURES
Two-level OCP with 96mS delay time Peak-current-mode operation with cycle-by-cycle current limiting PWM frequency continuously decreasing w/ burst mode at light loads Low start-up current (8uA) Low operating current (3.7mA) VDD over-voltage protection (OVP) AC input brownout protection with hysteresis Programmable over-temperature protection (OTP) Constant power limit over universal AC input range Internal latch circuit for OTP, OVP, OCP Very few external components
APPLICATIONS
General-purpose switch mode power supplies and flyback power converters, including: Power adapters Open-frame SMPS Specifically fit for SMPS with surge-current output, such as for printers, scanners, motor drivers, etc.
DESCRIPTION
The highly integrated SG6846 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 continuously decrease
TYPICAL APPLICATION
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Product Specification Highly-Integrated Green-Mode PWM Controller
SG6846 PIN CONFIGURATION
MARKING DIAGRAMS
8 F: L = OTP Latch C = Hysteresis OTP T: D = DIP, S = SOP
SG6846FTP
MXXXXXXYYWWV
P: Null = regular Z = Lead free M: Mask version XXXXXX: Wafer Lot YY: Year; WW: Week V: Assembly Location
GND FB VIN RI
1 2 3 4
8 7 6 5
GATE VDD SENSE RT
1
ORDERING INFORMATION
Part Number
SG6846LS SG6846LD SG6846CS SG6846CD SG6846LSZ SG6846LDZ SG6846CSZ SG6846CDZ
Package
8-Pin SOP 8-Pin DIP 8-Pin SOP 8-Pin DIP 8-Pin SOP (Lead Free) 8-Pin DIP (Lead Free) 8-Pin SOP (Lead Free) 8-Pin DIP (Lead Free)
OTP Mode
Latch off Latch off Hysteresis Hysteresis Latch off Latch off Hysteresis Hysteresis
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Product Specification Highly-Integrated Green-Mode PWM Controller
SG6846
PIN DESCRIPTIONS
Pin No. Symbol
1 2 GND FB
Function
Ground Feedback Line-voltage Detection Reference Setting Temperature Detection
Description
Ground. The signal from the external compensation circuit is fed into this pin. This FB pin and the current-sense signal from Pin 6 determine the PWM duty cycle. Line-voltage detection. The line-voltage detection is used for brownout protection with hysteresis. Constant output power limit over universal AC input range is also achieved using this VIN signal. It is suggested to add low pass filter to filter out line ripple on bulk capacitor. A resistor from the RI pin to ground will generate a reference current source inside SG6846. This determines the switching frequency. Increasing the resistance will reduce the switching frequency. Using a 26k resistor Ri results in a 65kHz switching frequency. For over-temperature protection. An external NTC thermistor is connected from this pin to GND pin. The impedance of the NTC will decrease at high temperatures. Once the voltage of the RT pin drops below a threshold, PWM output will be disabled. Current sense. The sensed voltage is used for peak-current-mode control and cycle-by-cycle current limiting. If the switching current is higher than 2/3 of the peak-current threshold for longer than 96ms, over-current protection will be activated. This two-level OCP feature is especially suitable for SMPS with surge current output. Power Supply. The internal protection circuit will disable PWM output when VDD over voltage. The totem-pole output driver for the power MOSFET. A soft driving waveform is implemented for improved EMI.
3
VIN
4
RI
5
RT
6
SENSE
Current Sense
7 8
VDD GATE
Power Supply Driver Output
BLOCK DIAGRAM (OTP LATCH VERSION)
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Product Specification Highly-Integrated Green-Mode PWM Controller
SG6846
ABSOLUTE MAXIMUM RATINGS
Symbol
VDD VL PD R J-C TJ TSTG TL
Parameter
Supply Voltage Input Voltage to VIN, FB, SENSE, RT, RI Pin Power Dissipation Thermal Resistance Operating Ambient Temperature Storage Temperature Range Lead Temperature (Soldering)
Test Condition
Value
25 -0.3 to 7V
Unit
V V mW C/W C C C
at T A < 50C Junction-Case
DIP SOP DIP SOP
800 400 67.1 41.2 -40 to 125 -65 to +150
10 sec 10 sec
DIP SOP
260 230
*All voltage values, except differential voltages, are given with respect to GND pin. *Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device.
RECOMMENDED OPERATING JUNCTION TEMPERATURE: -30C ~ 85C*
*For proper operation
ELECTRICAL CHARACTERISTICS (VDD = 15V, T A = 27C, unless noted) VDD Section
Symbol
VOP VTH-ON VTH-OFF IDD-ST IDD-OP VDD-OVP TVDD-OVP IDD-OVP VDD-TH-G
Parameter
Continuously Operating Voltage On Threshold Voltage Off Threshold Voltage Start-Up Current Operating Supply Current VDD Over Voltage Protection (Latch off) VDD OVP Debounce Time VDD OVP Latch-up Holding Current VDD Low-threshold Voltage to Exit Green-OFF Mode
Test Condition
Min.
15.5 9.5
Typ.
16.5 10.5 8 3.7
Max.
20 17.5 11.5 30 5 24.6
Unit
V V V uA mA V usec uA V
VDD = 15V GATE Open 22.6 RI = 26K VDD = 5V, TA = 27 C
o
23.6 100 45 VTH(OFF) + 1.25
VIN Section
Symbol
VIN-OFF VIN-ON
Parameter
PWM Turn-off Threshold Voltage PWM Turn-on Threshold Voltage
Test Condition
Min.
0.67
Typ.
0.72 VIN-OFF + 0.2
Max.
0.77
Unit
V V
Feedback Input Section
Symbol
AV ZFB VFB0
Parameter
Input-Voltage to Current-Sense Attenuation Input Impedance FB Pin open voltage
Test Condition
Min.
4
Typ.
1/4.2 5.5 6.2
Max.
7
Unit
V/V K V
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Product Specification Highly-Integrated Green-Mode PWM Controller
SG6846
Current Sense Section
Symbol
ZCS TPD BNK VTH-P @VIN=1V VTH-P @VIN=3V VTH-O @VIN=1V VTH-O @VIN=3V TDELAY-OCP
Parameter
Input Impedance Delay to Output Leading Edge Blanking Time Threshold Voltage for Current Limit Threshold Voltage for Current Limit 2/3 Threshold Voltage for Current Limit 2/3 Threshold Voltage for Current Limit The Delay Time for Over-current Protection
Test Condition
Min.
Typ.
12 100 360
Max.
200
Unit
k nsec nsec V V V V msec
VIN = 1V, RI = 26k VIN =3V, RI = 26k VIN = 1V, RI = 26k VIN =3V, RI = 26k RI = 26K
0.83 0.70 0.61 0.51 96
Oscillator Section
Symbol
FOSC FOSC-GREEN VN VG SG FDV FDT
Parameter
PWM Frequency Green-mode Frequency FB Pin Threshold for the Beginning of Green Mode Green-OFF Mode Voltage at FB pin Slope for Green-Mode Modulation Frequency Variation Versus VDD Deviation Frequency Variation Versus Temp. Deviation
Test Condition
RI = 26k RI = 26k
Min.
60 20
Typ.
65 22.5 2.1 1.6
Max.
70 25
Unit
KHz KHz V V Hz/mV
RI = 26k VDD = 11.5V to 20V TA = -30 to 85
85 5 1.5 5
% %
Frequenc y
FOSC: 65kHz
PWM Frequency
SG: 85Hz/mV
FOSC-GREEN: 22.5kHz
FOSC-GOFF: 0kHz VG: 1.6V VN: 2.1V
VF
B
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Product Specification Highly-Integrated Green-Mode PWM Controller
SG6846
PWM Section
Symbol
DMAX VOL VOH TR TF VCLAMP
Parameter
Maximum Duty Cycle Output Voltage Low Output Voltage High Rising Time Falling Time Gate Output Clamping Voltage
Test Condition
VDD = 15V, Io = 50mA VDD = 12V, Io = 50mA VDD = 15V, CL=1nF VDD = 15V, CL=1nF VDD = 20V
Min.
80 8V
Typ.
85
Max.
90 1.5
Unit
% V V nsec nsec V
350 50 18
Over Temperature Protection Section
Symbol
IRT VOTP-LATCH-OFF
Parameter
Output Current of RT Pin Threshold Voltage for Over-Temperature Protection.
Test Condition
RI = 26k
Min.
64 1.015
Typ.
70 1.065
Max.
76 1.115
Unit
uA V
TDOTP-LATCH VOTP-RESET
Over-Temperature Latch-Off Debounce. OTP Release Voltage (for non-latch-off version)
RI = 26k
100 VOTP-LATCHOFF
usec V
+ 0.1
RI Section
Symbol
RINOR RIMAX RIMIN
Parameter
RI Operating Range Max. RI value for Protection Min. RI value for Protection
Test Condition
Min.
15.5
Typ.
216 6
Max.
36
Unit
k k k
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Product Specification Highly-Integrated Green-Mode PWM Controller
SG6846
TYPICAL CHARACTERISTICS
Start-up Threshold Voltage vs Temperature
17.5
Min. Opperating Voltage vs Temperature
11.5 11.3
17.0
11.1
VTH-OFF (V)
VTH-ON (V)
10.9 10.7 10.5 10.3 10.1 9.9 9.7
16.5
16.0
15.5 -40 -25 -10 5 20 35 50 65 80 95 110 125
9.5 -40 -25 -10 5 20 35 50 65 80 95 110 125
Temperature ()
Temperature ( )
Start-up Current vs Temperature
16.000
Start-up Current vs VDD Voltage
20 16
15.500
IDD-ST (uA)
IDD-ST (uA)
-40 -25 -10 5 20 35 50 65 80 95 110 125
15.000
12 8 4 0 5 10 15 20
14.500
14.000
13.500
Temperature ()
VDD (V)
PWM Turn-off Threshold Voltage vs Temperature
1.000 0.900
PWM Turn-on Threshold Voltage vs Temperature
1.000 0.900
V IN-OFF (V)
VIN-ON (V)
0.800 0.700 0.600 0.500 0.400 -40 -25 -10 5 20 35 50 65 80 95 110 125
0.800 0.700 0.600 0.500 0.400 -40 -25 -10 5 20 35 50 65 80 95 110 125
Temperature ( )
Temperature ( )
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Product Specification Highly-Integrated Green-Mode PWM Controller
SG6846
PWM Frequency vs Temperature
65.300
PWM Frequency vs FB Voltage (RI = 26K)
PWM Frequency (Khz)
-40 -25 -10 5 20 35 50 65 80 95 110 125
65.200
60
FOSC (Khz)
65.100 65.000 64.900 64.800 64.700 64.600
40
20
0 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3
Temperature ()
VFB (V)
Current-limit Threshold vs VIN Voltage
1 0.8
2/3 Current-limit Threshold vs VIN Voltage 1 0.8 VTH-O (V) 0.6 0.4 0.2 0
VTH-P (V)
0.6 0.4 0.2 0 1 1.5 2 2.5 3
1
1.5
2 VIN (V)
2.5
3
VIN (V)
Output Current of pin RT vs Temperature
78.000 77.000
OTP Threshold Voltage vs Temperature
1.115
1.095 75.000 74.000 73.000 72.000 71.000 70.000 -40 -25 -10 5 20 35 50 65 80 95 110 125 1.015 -40 -25 -10 5 20 35 50 65 80 95 110 125
VOTP-OFF (V)
76.000
IRT (uA)
1.075
1.055
1.035
Temperature ()
Temperature ()
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Product Specification Highly-Integrated Green-Mode PWM Controller
SG6846
This current is used to determine the PWM frequency. Increasing the resistance will decrease the amplitude of the current source and reduce the PWM frequency. Using a 26k resistor Ri results in a corresponding 65kHz switching frequency. The relationship between RI and the switching frequency is:
OPERATION DESCRIPTION Start-up Operation
The turn-on/turn-off thresholds are fixed internally at 16.5V/10.5V. To enable the SG6846 during start-up, the hold-up capacitor must first be charged to 16.5V through the start-up resistor. The hold-up capacitor will continue to supply VDD before energy can be delivered from the auxiliary winding of the main transformer. The VDD must not drop below 10.5V during this start-up process. This UVLO hysteresis window ensures that the hold-up capacitor can adequately supply VDD during start-up. The typical start-up current is only 8uA. This allows a high resistance, low-wattage start-up resistor to be used, to minimize power loss. A 1.5 M/0.25W, start-up resistor and a 10uF/25V VDD hold-up capacitor would be sufficient for a universal input range. The required operating current has been reduced to 3.7mA. This enables higher efficiency and reduces the VDD hold-up capacitance requirement.
fPWM (kHz) =
1690 Ri (k )
---------------------------- (1)
If an open circuit or short circuit to ground occurs at the RI pin, the internal protection circuit will immediately shut down the controller.
Two-level Over-current Protection
The cycle-by-cycle current limiting will shut down the PWM immediately when the switching current is over the peak-current threshold. Additionally, when the switching current is higher than 2/3 of the peak-current threshold, the internal counter starts counting up. When the switching current is lower than 2/3 of the peak current threshold, the internal counter will count down. When the total accumulated counting time is more than about 96ms (Ri = 26kohm), the controller will be latched off. This two-level OCP protection and up/down counter are especially designed for SMPS with surge current output such as those for printers, scanners, motor drivers, etc.
Green-Mode Operation
The proprietary green-mode function provides off-time modulation to continuously decrease the switching frequency under light-load conditions. Maximum on time is limited to provide protection against abnormal conditions. To further reduce power consumption under zero-load condition, the PWM oscillator will be completely turned off, and the power supply will enter burst-mode. After the PWM oscillator is turned off, the IC's supply voltage VDD will drop gradually. Before the VDD voltage drops below the UVLO threshold, the PWM oscillator will be turned on again. This green-mode function dramatically reduces power consumption under light-load and zero-load conditions. Power supplies using the SG6846 can easily meet even the most restrictive international regulations regarding standby power consumption.
Constant Output Power Limit
For constant output power limit over universal input-voltage range, the peak-current threshold is adjusted by the voltage of the VIN pin. Since the VIN pin is connected to the rectified AC input line voltage through the resistive divider, a higher line voltage will generate a higher VIN voltage. The threshold voltage decreases as the VIN voltage increases, making the max. output power at high line input voltage equal to that at low line input.
Brownout Protection
Since the VIN pin is connected through a resistive divider to the rectified AC input line voltage, it can also be used for brownout protection. If the VIN voltage is less A resistor connected from the RI pin to GND than 0.72V, the PWM output will be shut off. As the VIN generates a reference current source inside the SG6846. (c) System General Corp. -9www.sg.com.tw Version 1.0(IAO33.0008.B0) Sep. 30, 2004
Oscillator Operation
Product Specification Highly-Integrated Green-Mode PWM Controller voltage over 0.92V, the PWM output will be turned on again. The hysteresis window for ON/OFF is around 0.2V.
SG6846
RT pin drops below 1.065V, the SG6846 will be turned off. There are two options for the protection modes, please see ORDER INFORMATION.
Noise immunity VDD Over-voltage Protection
VDD over-voltage protection is built in to prevent the controller from over-voltage destruction. When VDD voltage is over 23.6V, the SG6846 is latched off. Noise from the current sense or the 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. The designer should avoiding long PCB traces and component leads. Compensation and filter components should be located near the SG6846.
Over-temperature Protection
An external NTC thermistor can be connected from the RT pin to GND. The impedance of the NTC will decrease at high temperatures. When the voltage of the
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Product Specification Highly-Integrated Green-Mode PWM Controller
SG6846
REFERENCE CIRCUIT Application circuit for 32V/16V output
P1
t
F1
RT1
2 4 3 1
CY1 CY2
CX1LF2
BD1
1 2 5
TX1
13 +
R16 D4
1 2 2 3
VZ1 P2 P7 LF1
1 3 4 2
2
R8
3 1
C2
R12 C4
1
6
+
2
CX2
4
P32V P32V L1 C16+
1
2
C12
+
32V C13
32V
1
R1
R2 R3
2
R9
1 +
2
7 1 3
9
C11
R17 P16V P16V L2 C17+
2 +
11 1 2 3
D1
21 2
L4
12
D3
2
1
D2
10
2
2 1
R4
1
C3
C5
1
+
R11 D5
C14
+
16V 16V C15
1
U1
1 GND FB VIN RI GATE VDD SENSE RT 8 7 6 5
2
R13 R6 R10 NTC1 C6
Q1
1 2
FB
2
2 3
L3 R14
P16V
C1
1
+
R5
4
R7
1
3
P16V R15
4
FB
1
FB C7
C9 U2
3 2 K R
P16V R18
P16V
1 P32V
P32V
R19 R21
R20
U3
A
BOM PART NO.
R1, R2, R3, R4 R8, R9 R5 R15 R13 R18 R21 R7 R6 R19 R14 R16, R17 R11 R12 R20 R22
VALUE
470K +/-5% S1M +/-1% 16K2 +/-1% 1K5 +/-5% 10 +/-5% 4K7 +/-5% 15K +/-1% 27K +/-5% 330 +/-1% 102K +/-1% 022 +/-5% 1W 20 +/-5% 20K +/-5% 100K +/-5% 887K +/-1% 10K +/-1%
PART NO.
C4 C10,C11 C6,C7 C9 C14,C17 C15 C13,C16 C2 C1 C3 CX1 C8 C5 CX2 D1 D2
VALUE
103 P 630V 102 P 1KV 102 P 50V 222 P 50V 470u 25V 220u 25V 220u 50V 150u 400V 4u7 50V 10u 50V X1 0.47u 275V Y2 222P 250V 100u 50V X2 0.1uF 275V 1N4148 BYV95C
PART NO.
D3 BD1 D4 D5 F1 L1,L2 L4 U3 U1 U2 Q1 TX1 RT1 VZ1
VALUE
FR103 1.0A 200V DBL406G BYT28-300 BYV32-150 250V4A QUICK 1.8uH 10uH TL431 +/-1% SG 6846 PC817 7NB60 EI-33 SCK053 14 470V
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Product Specification Highly-Integrated Green-Mode PWM Controller
SG6846
PACKAGE INFORMATION DIP-8 Outline Dimensions
D
8 5
E1
E
eB
1
4
A1
A2
L b1 b e
Dimension
Symbol A A1 A2 b b1 D E E1 e L eB Millimeter Min. 0.381 3.175 Inch Min. 0.015 0.125
Typ.
Max. 5.334 3.429
A
Typ.
Max. 0.210 0.135
9.017 6.223 2.921 8.509 0
3.302 1.524 0.457 9.271 7.620 6.350 2.540 3.302 9.017 7
10.160 6.477 3.810 9.525 15
0.355 0.245 0.115 0.335 0
0.130 0.060 0.018 0.365 0.300 0.250 0.100 0.130 0.355 7
0.400 0.255 0.150 0.375 15
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Product Specification Highly-Integrated Green-Mode PWM Controller
SG6846
SOP-8 Outline Dimensions
8
5
C
1 b
4 e
D
A1
A
Dimension:
Symbol A A1 b c D E e F H L Millimeter Min. 1.346 0.101 Inch Min. 0.053 0.004
Typ.
Max. 1.752 0.254
0.406 0.203 4.648 3.810 1.270 0.381X45 5.791 0.406 0 6.197 1.270 8 0.228 0.016 0 4.978 3.987 0.183 0.150
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H F
E
L
Typ.
Max. 0.069 0.010
0.016 0.008 0.196 0.157 0.050 0.015X45 0.244 0.050 8
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Product Specification Highly-Integrated Green-Mode PWM Controller
SG6846
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 other applications in which failure of 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. (c) System General Corp. Version 1.0(IAO33.0008.B0) - 14 www.sg.com.tw Sep. 30, 2004

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