UC3843DX Fairchild Semiconductor, UC3843DX Datasheet - Page 7
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UC3843DX
Manufacturer Part Number
UC3843DX
Description
IC CTLR PWM CURR MODE 14-SOIC
Manufacturer
Fairchild Semiconductor
Datasheet
1.UC3842D.pdf
(12 pages)
Specifications of UC3843DX
Pwm Type
Current Mode
Number Of Outputs
1
Frequency - Max
500kHz
Duty Cycle
100%
Voltage - Supply
8.2 V ~ 30 V
Buck
No
Boost
No
Flyback
No
Inverting
No
Doubler
No
Divider
No
Cuk
No
Isolated
No
Operating Temperature
0°C ~ 70°C
Package / Case
14-SOIC (3.9mm Width), 14-SOL
Frequency-max
500kHz
Duty Cycle (max)
100 %
Output Current
1000 mA
Mounting Style
SMD/SMT
Switching Frequency
500 KHz
Operating Supply Voltage
30 V
Supply Current
17 mA
Maximum Operating Temperature
+ 70 C
Fall Time
35 ns
Minimum Operating Temperature
0 C
Rise Time
45 ns
Synchronous Pin
No
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Shutdown of the UC3842 can be accomplished by two methods; either raise pin 3 above 1V or pull pin 1 below a voltage two
diode drops above ground. Either method causes the output of the PWM comparator to be high (refer to block diagram). The
PWM latch is reset dominant so that the output will remain low until the next clock cycle after the shutdown condition at pins
1 and/or 3 is removed. In one example, an externally latched shutdown may be accomplished by adding an SCR which will be
reset by cycling V
A fraction of the oscillator ramp can be resistively summed with the current sense signal to provide slope compensation for
converters requiring duty cycles over 50%. Note that capacitor, C
spikes.
Figure 10. Temperature Drift (Vref)
Figure 12. Temperature Drift (Icc)
CC
below the lower UVLO threshold. At this point the reference turns off, allowing the SCR to reset.
Temperature ( C)
Temperature ( C)
UC3842/UC3843
Figure 9. Slope Compensation
T
, forms a filter with R2 to suppress the leading edge switch
Figure 11. Temperature Drift (Ist)
Temperature ( C)
UC3842/UC3843/UC3844/UC3845
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