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Product Specification Highly Integrated Green-Mode PWM Controller
SG6846A
consumption, a proprietary green-mode function provides off-time modulation to continuously decrease the switching frequency under light-load conditions. Under zero-load conditions, the power supply enters burst-mode. The SG6846A is especially designed for SMPS with surge-current output, incorporated with a two-level OCP function. Besides the cycle-by-cycle current limiting, if the switching current is higher than two thirds the peak-current threshold for 1700ms, over-current protection is activated and the SG6846A latches off. If the switching current is higher than two thirds the peak-current threshold for 100ms and the voltage on the VDD pin is higher than VDD-OFF + 1V, the PWM pulses are latched off immediately once VDD voltage is lower than VDD-OFF + 1V; useful if an output short-circuit occurs. SG6846A also integrates a frequency hopping function that reduces EMI emission of a power supply with minimum line filters. Its built-in synchronized slope compensation provides proprietary internal compensation for constant output power limit over a universal AC input range. Also, the gate output is clamped at 18V to protect the external MOSFET from over-voltage damage. Internal soft-start is built-in to reduce stress on the MOSFET and start-up current during power-on period. Other protection functions include: AC input brownout protection with hysteresis, VDD over-voltage protection, and over-temperature 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 PWM pulses stay latched off until the power supply is unplugged from the main outlet. SG6846A is available in an 8-pin SOP package.
FEATURES
Two-level OCP with 1700ms delay time Output short-circuited delay time: 100ms Low start-up current (8A) Low operating current (3.7mA) Peak-current mode operation with cycle-by-cycle current limiting
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Programmable PWM frequency with frequency hopping PWM frequency continuously decreasing with burst mode at light loads VDD over-voltage protection (OVP) AC input brownout protection with hysteresis and constant output power limit Constant output power limit (full AC input range) Internal latch circuit for OVP, OTP, and OCP Built-in soft-start Open-loop protection with 1700ms delay time
APPLICATIONS
General-purpose switch-mode power 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.) supplies and
DESCRIPTION
The highly integrated SG6846A series of PWM controllers provides features to enhance the performance of flyback converters. To minimize standby power
TYPICAL APPLICATION
(c) System General Corp. Version 1.1.1 (IAO33.0059.B1)
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6846A PIN CONFIGURATION
MARKING DIAGRAMS
F: L=OCP Latch, C=OCP auto-recovery T: S=SOP P : Z=Lead Free Null=regular package XXXXXXXX: Wafer Lot Y: Year; WW: Week V: Assembly Location
GND FB VIN RI
GATE VDD SENSE RT
SG6846AFTP
XXXXXXXXYWWV
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ORDERING INFORMATION
Part Number
SG6846ALSZ SG6846ACSZ (Preliminary)
OCP Latch
Yes No
Pb-Free
Package
8-Pin SOP 8-Pin SOP
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. The PWM duty cycle is determined in response to the signal from this pin and the current-sense signal from Pin 6. Line-voltage detection. The line-voltage detection is used for brownout protection with hysteresis. Constant output power limit over a universal AC input range is also achieved using this VIN pin. Consider adding a low-pass filter to filter out line ripple on the bulk capacitor. A resistor from the RI pin to ground generates a reference current source that determines the switching frequency. Increasing the resistance reduces the switching frequency. Using a 26k resistor results in a 65kHz switching frequency. For over-temperature protection, an external NTC thermistor is connected from this pin to the GND pin. The impedance of the NTC decreases at high temperatures. Once the voltage of the RT pin drops below a threshold, PWM output is disabled.
3
VIN
4
RI
5
RT
6
SENSE
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 two thirds of the peak-current threshold for longer than 100ms and VDD is higher than 12V and lasts for 1700ms, over-current Current Sense protection is activated. If an output short over-current also occurs and lasts for 100ms and VAUX is lower than 12V, SG6846A turns off immediately. This two-level OCP feature is especially suitable for SMPS with surge current output. It also has built-in 5ms soft-start time as switching frequency operates at 65KHz. Power Supply Driver Output Power supply. If an open-circuit failure occurs in the feedback loop, the internal protection circuit disables PWM output as long as VDD exceeds the threshold. The totem-pole output driver for the power MOSFET, internally clamped below 18V.
7 8
VDD GATE
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6846A
BLOCK DIAGRAM
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6846A
ABSOLUTE MAXIMUM RATINGS
Symbol
VVDD VL PD RJC TJ TSTG T www..comL ESD
Parameter
Supply Voltage Input Voltage to VIN, FB, SENSE Pins Power Dissipation Thermal Resistance (Junction-to-Case) Operating Junction Temperature Storage Temperature Range Lead Temperature (Wave Soldering or Infrared, 10 Seconds) Electrostatic Discharge Capability, Human Body Model Electrostatic Discharge Capability, Machine Model
Value
25 -0.3 to 7.0 400 54.4 -40 to +125 -65 to +150 260 5.0 200
Unit
V V mW C/W C C C kV V
* 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
Symbol
TA
Parameter
Operating Ambient temperature
Value
-20C ~ 85C
Unit
V
*For proper operation
ELECTRICAL CHARACTERISTICS
VDD=15V, TA=25C, unless otherwise noted.
VDD SECTION
Symbol Parameter
VDD-OP VDD-ON VDD-OFF IDD-ST IDD-OP VDD-OVP tD-VDDOVP IDD-OVP VDD-SCP Continuously Operating Voltage Turn-on Threshold Voltage Turn-off Voltage Start-Up Current Operating Supply Current VDD Over-Voltage Protection (Latch off) VDD OVP Debounce Time VDD OVP Latch-up Holding Current Threshold Voltage on VDD for Short-Circuit Protection RI=26K VDD=5V VCS>VSTH lasts for TDELAY-Short VDD-ON - 0.16V GATE open 22.6 23.6 100 70 15.5 9.5 16.5 10.5
Test Condition
Min.
Typ.
Max.
20 17.5 11.5 30 5 24.6
Unit
V V V A mA V s A
VDD-OFF + 0.5V VDD-OFF + 1V VDD-OFF + 1.5V V
VIN SECTION
Symbol
VIN-OFF VIN-ON
Parameter
PWM Turn-off Threshold Voltage PWM Turn-on Threshold Voltage
Min.
0.65 VIN-OFF+0.18
Typ.
0.70 VIN-OFF+0.2
Max.
0.75 VIN-OFF+0.22
Unit
V V
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6846A
FEEDBACK INPUT SECTION
Symbol Parameter
AV ZFB VFB-OPEN VFB-OLP tD-OLP Input Voltage to Current-Sense Attenuation Input Impedance FB Pin Open Voltage FB Open-Loop Trigger Level Delay Time of FB Pin Open-Loop Protection RI=26K 5.6 4.7 1600
Test Condition
At Green Mode
Min.
Typ.
1/4 5.5 6.2 5.2 1700
Max.
Unit
V/V k
6.6 5.7 1800
V V ms
CURRENT-SENSE SECTION
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Symbol Parameter
ZSENSE tPD tLEB VSTH1V VSTH3V VSTH1V-2/3 VSTH3V-2/3 tD-OCP VSLOPE tD-Short tSS-65KHz tSS-130KHz 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 *Delay Time for Over-Current Protection Slope Compensation *Output Short Delay Time Soft-Start Time Soft-Start Time
Test Condition
Min.
Typ.
12
Max.
250
Unit
k ns ns V V
270 VIN=1V VIN=3V VIN=1V VIN=3V RI=26K Duty=DCYMAX VCS> VSTH, RI=26K RI=26K RI=13K 92 0.58 0.48 1500
360 0.83 0.70 0.61 0.51 1600 0.33 100 5 2.5 108 0.64 0.54 1700
V V ms V ms ms ms
OSCILLATOR SECTION
Symbol Parameter
FOSC FOSC,MAX FOSC,MIN thop-1 FOSC-G VFB-N VFB-G SG FDV FDT Normal PWM Frequency Maximum PWM Frequency Minimum PWM Frequency Jitter Period Green-Mode Minimum Frequency FB Pin Frequency Reduction Threshold FB Voltage at FOSC-GREEN Slope for Green-Mode Modulation Frequency Variation vs. VDD Deviation Frequency Variation vs. Temperature Deviation Pin, FB Voltage Jitter Range Pin, FB Voltage Jitter Range Center Frequency Jitter Range Center Frequency Jitter Range Center Frequency Jitter Range
Test Condition
RI=26K, VFB>VN RI=13K, VFB>VN RI=36K, VFB>VN RI=26K, VFB>VN RI=26K RI=26K, VFB=VN RI=26K, VFB=VG RI=26K VDD=11.5V to 20V TA=-20 to 85 C
Min.
62 124 44.8
Typ.
65 4.2 130 8.4 47.0 2.9 4.4
Max.
68 136 49.2
Unit
kHz kHz kHz ms
18.0
22.5 2.1 4.2 1.6 1.45 85
25.0
kHz V KHz V KHz Hz/mV
5 1.5 5.0
% %
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6846A
Frequency
+4.2KHz 65kHz -4.2KHz
PWM Frequency
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+1.45KHz 22.5kHz -1.45KHz
V FB-G
V FB-N
VFB
PWM OUTPUT SECTION
Symbol
DCYMAX VGATE-L VGATE-H tR tF VGATE-CLAMP
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 GATE=1nF GATE=1nF VDD=20V
Min.
Typ.
Max.
90 1.5
Unit
% V V ns ns
8 350 50 18
V
OVER-TEMPERATURE PROTECTION SECTION
Symbol
IRT VRTTH tD-OTP
Parameter
Output Current of RT Pin Threshold Voltage for Over-Temperature Protection Over-Temperature Latch-Off Debounce
Test Condition
RI=26K
Min.
64 1.015
Typ.
70 1.065 100
Max.
76 1.115
Unit
A V ms
RI=26K
RI SECTION
Symbol
RINOR
Parameter
RI Operating Range
Test Condition
Min.
13
Typ.
Max.
36
Unit
k
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6846A
TYPICAL CHARACTERISTICS
Turn-on Threshold Voltage (VDD-ON) vs Temperature 20 18 VDD-ON (V) 16 14 12 10 -40 -25 -10 5 20 35 50 65 80 95 110 125
11.5 11.1 VDD-OFF (V) 10.7 10.3 9.9 9.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature () Turn-off Voltage (VDD-OFF) vs Temperature
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Temperature ()
Start-Up Current (IDD-ST) vs Temperature
Start-Up Current vs VDD Voltage
30.0 26.8
10 8
IDD-ST (uA)
23.6 20.4 17.2 14.0 -40 -25 -10 5 20 35 50 65 80 95 110 125
IDD-ST (uA)
6 4 2 0 10 11 12 13 14 15 16
Temperature ( )
VDD (V)
PWM Turn-off Threshold Voltage (VIN-OFF) vs Temperature
PWM Turn-on Threshold Voltage (VIN-ON) vs Temperature
2.5
1.00
2.0
0.98
VIN-OFF (V)
1.5
VIN-ON (V)
0.96
1.0
0.94
0.5
0.92
0.0 -40 -24 -7 10 26 43 59 76 92 109 125
0.90 -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
Normal PWM Frequency (F OSC ) vs Temperature
PWM Frequency vs FB Voltage
SG6846A
68
70
67
PWM Frequency (kHz
-40 -25 -10 5 20 35 50 65 80 95 110 125
56
F OSC (kHz)
66
42
64
28
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63
14
62
0 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4
Temperature ( )
VFB (V)
Current - limit Threshold vs Vin Voltage
2/ Current - limit Threshold vs Vin Voltage 3
0.90 0.85 0.80 0.75 0.70 0.65 0.60
0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9 3.1 3.3
0.90
0.82
VTH-O (V)
VTH-P (V)
0.74
0.66
0.58
0.50 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9 3.1 3.3
VIN ( V )
VIN (V)
Output Current of RT Pin (I ) vs Temperature RT
FB Output High Voltage (VRTTH) vs Temperature
71.0
1.4
70.5
1.2
70.0
VRTTH (V)
IRT (uA)
1.0
69.5
0.8
69.0
0.6
68.5 -40 -25 -10 5 20 35 50 65 80 95 110 125
0.4 -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
SG6846A
OPERATION DESCRIPTION
Start-up Operation The turn-on/turn-off thresholds are fixed internally at 16.5V/10.5V. To enable the SG6846A during start-up, the hold-up capacitor must first be charged to 16.5V through the start-up resistor. The hold-up capacitor continues to supply VDD before energy can be delivered from the auxiliary winding of the www..com 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 8A, which allows a high-resistance, low-wattage start-up resistor to minimize power loss. A 1.5M/0.25W start-up resistor and a 10F/25V VDD hold-up capacitor are sufficient for a universal input range. The required operating current has been reduced to 3.7mA, which enables higher efficiency and reduces the VDD hold-up capacitance requirement. corresponding 65kHz switching frequency. The relationship between RI and the switching frequency is:
fPWM(kHz) = R1690 ) (k
I
----------------------------
(1)
If an open-circuit or short-circuit to ground occurs at the RI pin, the internal protection circuit immediately shuts down the controller.
Two-Level Over-Current Protection The cycle-by-cycle current limiting shuts down the PWM immediately when the switching current is over the peak-current threshold. Additionally, when the switching current is higher than two thirds the peak-current threshold, the internal counter counts down. When the total accumulated counting time is more than around 1600ms (RI=26k), the controller is latched off the internal counter counting up. When the switching current is lower than two thirds of the peak current threshold, the internal counter counts down. When the total accumulated counting time is more than about 1700ms (RI=26k), the controller is latched off. This two-level OCP protection and up/down counter are especially designed for SMPS with surge current 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 is completely turned off and the power supply enters burst-mode. This green-mode function dramatically reduces power consumption under light-load and zero-load conditions. Power supplies using the SG6846A can meet even the most restrictive international regulations regarding standby power consumption.
Constant Output Power Limit For constant output power limit over a 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 generates a higher VIN voltage. The threshold voltage decreases as the VIN voltage increases, making the maximum output power at high-line input voltage equal to that at low-line input.
Oscillator Operation A resistor connected from the RI pin to GND generates a reference current source used to determine the PWM frequency. Increasing the resistance decreases the amplitude of the current source and reduces the PWM frequency. Using a 26k resistor results in a
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6846A
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 than 0.7V, the PWM output shuts off. If the VIN voltage is over 0.9V, the PWM output turns on again. The hysteresis window for ON/OFF is around 0.2V. V www..comDD 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 SG6846A is latched off.
Noise Immunity Noise from the current sense or the control signal may cause significant pulse jitter, particularly in continuous-conduction mode. Slope compensation helps alleviate this problem. Good placement and layout practices should be followed. Avoid long PCB traces and component leads. Compensation and filter components should be located near the SG6846A. Usually an RC network is put on between sensing resistor and the CS pin to filter high-frequency switching noise, as shown Figure 1.
Over-Temperature Protection An external NTC thermistor can be connected from the RT pin to GND. The impedance of the NTC decreases at high temperatures. When the voltage of the RT pin drops below 1.065V, the SG6846A is turned off. For the protection modes options, please see ORDER INFORMATION.
FIG-1 Current Sense RC Filter
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6846A
REFERENCE CIRCUIT
Application Circuit for 32V/16V Output
P1
t
F1
RT1
2
4
3
VZ1 P2 P7 LF1 CY2
3 1
1
CY1
CX1LF2
4
BD1
1 2 5
TX1
13 +
R16 D4
1 2 2 3 10
2
2
R8
3 1
C2
R12 C4
1
6
+
2
CX2
4
P32V P32V L1 C12
2
C16+
1
+
32V C13
32V
1
R1
R2 R3
2
R9
1 +
C11
R17 P16V P16V L2 C17+
2 +
3
11 1 2 3
D1
21 2
L4
12
D3
2
1
D2
2
7 1
9
2
2 1
R4
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C3
C5
1
+
R11
C14
+
16V 16V C15
1
D5
1 1 P32V
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
P16V
C7 U2
3 2
C9
K R
P16V R18 R19 R21
P32V 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 470 25V 220 25V 220 50V 150 400V 47 50V 10 50V X1 0.47 275V Y2 222P 250V 100 50V X2 0.1F 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 1.8H 10H TL431 +/-1% SG 6846 PC817 7NB60 EI-33 SCK053 14 470V
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Product Specification Highly Integrated Green-Mode PWM Controller
SG6846A
PACKAGE INFORMATION8PINS-SOP(S)
8
5
C
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1 b
4 e
D
A1
A
Dimensions Millimeter Min. Typ.
1.346 0.101 0.406 0.203 4.648 3.810 1.016 5.791 0.406 0 4.978 3.987 1.524 6.197 1.270 8 0.183 0.150 0.040 0.228 0.016 0
Symbol
A A1 b c D E e F H L
Max.
1.752 0.254
1.270 0.381X45
(c) System General Corp. Version 1.1.1 (IAO33.0059.B1)
H F
E
L
Inch Min.
0.053 0.004
Typ.
0.016 0.008
Max.
0.069 0.010
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
SG6846A
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