CURRENT SENSE LATCH This monolithic integrated circuit analog lat
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SG1549/SG2549/SG3549
CURRENT SENSE LATCH
This monolithic integrated circuit analog latch device with digital reset. specifically designed provide pulse-by-pulse current limiting switch-mode power supply systems, many other application also feasible. function provide latching switch action upon sensing input threshold voltage, with reset accomplished external clock signal. This device interfaced directly with many kinds pulse width modulating control IC's, including SG1524, SG1525A SG1527A. input threshold latch circuit 100mV, which referenced either ground wide-ranging positive voltage. There high low-going output signals available, both supply voltage clock signal taken directly from associated control chip. With delays range nanoseconds, this latch circuit ideal fast reaction sensing provide overall current limiting, short circuit protection, transformer saturation control.
FEATURES
Current sensing with 100mV threshold Common-mode input ground Complementary outputs Automatic reset from clock 180ns delay Interface direct SG1524, SG1525A, SG1527A
HIGH RELIABILITY FEATURES SG1549
Available MIL-STD-883 level processing available Radiation data available
BLOCK DIAGRAM
SCHEMATIC
4/90 2/94
Copyright 1994
11861 Western Avenue Garden Grove, 92841 (714) 898-8121 FAX: (714) 893-2570
LINFINITY
Microelectronics Inc.
SG1549/SG2549/SG3549
ABSOLUTE MAXIMUM RATINGS (Note
Input Supply Voltage, Input Voltage Output "off" Voltage Output "on" current 25mA
Note Values beyond which damage occur.
Operating Junction Temperature Hermetic Package) 150°C Plastic Package) 150°C Storage Temperature Range -65°C 150°C
THERMAL DATA
Package: Thermal Resistance-Junction Case, 50°C/W Thermal Resistance-Junction Ambient, 130°C/W Package: Thermal Resistance-Junction Case, 60°C/W Thermal Resistance-Junction Ambient, 95°C/W
Note Junction Temperature Calculation: JA). Note above numbers maximums limiting
thermal resistance package standard mounting configuration. numbers meant guidelines thermal performance device/pcboard system. above assume ambient airflow.
RECOMMENDED OPERATING CONDITIONS (Note
Input Supply Voltage, 5.0V Input Voltage Output "off" Voltage Output "on" Current 10mA Reset Voltage 0.8V
Note Range over which device functional.
Reset Voltage 2.5V 5.0V Operating Ambient Temperature Range SG1549Y -55°C 125°C SG2549Y -25°C 85°C SG3549Y 70°C
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, these specifications apply over operating ambient temperatures SG1549 with -55°C 125°C, SG2549 with -25°C 85°C, SG3549 with 70°C, duty cycle pulse testing techniques used which maintains junction case temperatures equal ambient temperature.)
Parameter Supply Section Supply Current Input Section (Note Threshold Voltage Input Impedance Input Section (Note Threshold Voltage VPIN VPIN
Test Conditions
SG1549/2549 SG3549 Units Min. Typ. Max. Min. Typ. Max.
shorted, 25°C shorted VPIN 50mV, 25°C VPIN 50mV open, 25°C 40V, open, 25°C open 40V, open VPIN VPIN
Input Current Clock Reset Section Min. Trigger Voltage Input Current
VPIN
Note Input threshold voltages supply current directly proportional supply voltage,
4/90 2/94
Copyright 1994
11861 Western Avenue Garden Grove, 92841 (714) 898-8121 FAX: (714) 893-2570
LINFINITY
Microelectronics Inc.
SG1549/SG2549/SG3549
ELECTRICAL CHARACTERISTICS
over recomended operating temperature, unless otherwise specified.)
Parameter Output Section Voltage Voltage Output Leakage Voltage
Test Conditions
SG1549/2549 SG3549 Units Min. Typ. Max. Min. Typ. Max.
VPIN
(Note
TYPICAL SWITCHING CHARACTERISTICS
25°C)
Parameter Reset Minimum Pulse Width (TW1) Delay from Reset Output (TD(OFF)) Input Minimum Pulse Width (TW2) Delay from Input Output (TD(ON)) Delay from Input Output (TD(ON)) Delay from Output Output
Test Conditions Amplitude 3.0V Amplitude 200mV Amplitude 200mV, Amplitude 200mV, Input 200mV
SG1549 Series Units Min. Typ. Max.
Note These parameters, although guaranteed, tested production.
DYNAMIC TEST CIRCUIT
SWITCHING WAVEFORMS
APPLICATION NOTES
HIGH LINE SENSING SG1549 will provide current sensing positive supply line typical SG1524 single-ended switching regulator application shown Figure sense circuitry used with input voltages between volts. value determined dividing 100mV input threshold peak current desired. High-frequency noise, switching transients, usually eliminated small capacitor between pins Current control accomplished either OUTPUT connected SG1524's Shutdown pin, OUTPUT connected directly Compensation Terminal. either case, activation current sense latch will tend discharge compensation capacitor, which cause slow recovery from pulse limiting. this feature desired, OUTPUT used discharge soft-start network instead coupling directly SG1524. desired, small value perhaps diode across will enhance recovery.
FIGURE HIGH LINE SENSING WITH SG1549 CONJUNCTION WITH SG1524 CONTROL
4/90 2/94
Copyright 1994
11861 Western Avenue Garden Grove, 92841 (714) 898-8121 FAX: (714) 893-2570
LINFINITY
Microelectronics Inc.
SG1549/SG2549/SG3549
APPLICATION NOTES
(continued)
Another method introducing current shutdown signal shown Figure where SG1524 used activate constant drive current high-current switch, this case SM600. 2N2222 forms constant current generator when driven from SG1524's volt reference through resistor. This transistor then switched OUTPUT transistor SG1549, achieving fastest response output regulator. LINE SENSING many types feed-forward push-pull converters, current protection provided sensing emitter resistor referenced ground primary side output transformer. fast-reacting SG1549 easily sense secondary overload reflected back primary and, additionally, provide protection from unbalanced transformer saturation. When using inputs, inputs should shorted together. While inputs connected directly across sense resistor, small low-pass filter shown Figure often required eliminate high frequency transients. must remembered that input impedance terminals will cause increase effective threshold; however, this also offers possibility easily adjustable threshold incorporating potentiometer input. Coupling output signal from SG1549 control chip done several ways including either Compensation Shutdown pins SG1524 described earlier. Another convenient output SG1549 into control higher power applications using SG1627 Dual Interface Driver connecting OUTPUT terminal Sg1549 directly Non-Inverting inputs SG1627 shown Figure finally, keep mind that OUTPUT terminal SG1549 will easily drive most high-speed optical couplers should some type isolation between current sense shutdown control required.
FIGURE CURRENT CONTROL BUCK REGULATOR WITH CONSTANT DRIVE CURRENT
FIGURE PUSH-PULL CONVERTER WITH LOW-LINE EMITTER CURRENT SENSING
FIGURE POWER BOOST CURRENT CONTROL WITH SG1627
CONNECTION DIAGRAMS ORDERING INFORMATION
Package
8-PIN CERAMIC PACKAGE
(See Notes Below)
Part SG1549Y/883B SG1549Y/DESC SG1549Y SG2549Y SG3549Y SG2549M SG3549M
Ambient Temperature Range -55°C 125°C -55°C 125°C -55°C 125°C -25°C 85°C 70°C -25°C 85°C 70°C
Connection Diagram
INPUT INPUT INPUT INPUT
CLOCK RESET OUTPUT OUTPUT
8-PIN PLASTIC PACKAGE
Note Contact factory DESC product availability. 4/90 2/94
Copyright 1994
parts viewed from top.
11861 Western Avenue Garden Grove, 92841 (714) 898-8121 FAX: (714) 893-2570
LINFINITY
Microelectronics Inc.
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