UTC3843D

LINEAR INTEGRATED CIRCUIT UTC3843D/E CURRENT MODE PWM CONTROL CIRCUITS DESCRIPTION The UTC3843D/E provides the necessary features to implement off-line or DC to DC fixed frequency current mode control schemes with a minimal external parts count. Internally implemented circuits include under-voltage lockout featuring start up current less than 1mA,a precision reference trimmed for accuracy at the error amp input, logic to insure latched operation, a PWM comparator which also provides current limit control,and a totem pole output stage designed to source or sink high peak current.The output stage, suitable for driving N channel MOSFETs,is low in the off state. DIP-8 SOP-8 FEATURES *Optimized for off-line and DC to DC converts *Low start up current(15mA ON/OFF Command to rest of IC 7 Von=8.4V Voff=7.6V 5k ) INTERNAL CLOCK Timing Resistance Vs Frequency 100 100 td ( s) CT=1nF RT (k ) CT=2.2nF 10 CT=4.7nF 10 CT=10nF CT=22nF 1 CT=47nF CT=100nF 1 0.1 1 10 10 100 2 10 3 10 4 10 5 10 6 Frequency (Hz) CT (nF) YOUWANG ELECTRONICS CO.LTD 5 2006.07.11 LINEAR INTEGRATED CIRCUIT UTC3843 SHUTDOWN TECHNIQUES 1k Shutdown UTC3843D/E can be accomplished by two methods;either raise pin 3 above 1V or pull Pin 1 b el ow a volt age t w o diode drops above ground.Either method caused the output of PWM comparator to be high(refer to block diagram).The PWM latch is reset dominant so that the output will rem ain low until the next clock cycle after the shutdown condition at pins a and/or 3 is removed .In one example, an externally latched shut down may be accomplished by adding an SCR which be reset by cycling Vcc below the lower UVLO threshold. At this point tyhe reference turns off allowing the SCR to reset. 1 8 330 Shutdown 500 3 Shutdown To current Sense resistor TYPICAL PERFORMANCE CHARACTERISTICS Vref Temperature Drift Istart Temperature Drift 5.02 550 Vref (V) 5.01 500 Vcc=15V Io=1mA Vcc=9V 450 Istart (mA) 5.00 4.99 400 4.98 350 4.97 300 4.96 -50 -25 0 25 50 75 100 125 250 -50 150 -25 0 25 50 75 100 125 150 T T 15 Icc (mA) 14 Vcc=15V Io=1mA 13 12 11 10 9 -50 -25 0 25 50 75 100 125 150 T Icc Temperature Drift YOUWANG ELECTRONICS CO.LTD 6 2006.07.11 LINEAR INTEGRATED CIRCUIT UTC3843 4 100 80 Voltage Gain (dB) Saturation Voltage (V) 3 2 0 a = + 2 5 5 a = - 60 -45 40 -90 20 -135 0 -180 PHASE (Degree) Vcc=15V T T 1 0 0.01 0.1 1 10 Output Current (Sourse or Sink Current) (A) 2 10 10 3 10 4 10 5 10 6 10 7 Frequency (Hz) Output Saturation Characteristics Error Amplifier Open-Loop Frequency Response YOUWANG ELECTRONICS CO.LTD 7 2006.07.11 UTC3843 LINEAR INTEGRATED CIRCUIT PACKAGE DIMENSIONS DIP-8-300-2.54 SOP-8-225-1.27 YOUWANG ELECTRONICS CO.LTD 8 2006.07.11 LINEAR INTEGRATED CIRCUIT UTC3843 Attach Revision History Data REV 1.0 2006.07.11 1.1 Description Page Original Add “OREDRING INFORMATION”and package outline”SOP-8” YOUWANG ELECTRONICS CO.LTD 9 1,8 2006.07.11