UC3842A View Datasheet(PDF) - Unisonic Technologies
Part Name
Description
Manufacturer
UC3842A Datasheet PDF : 9 Pages
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UC3842A/3843A
CURRENT SENSE CIRCUIT
Is
1
R
3
Rs
C
5
Error Amplifier
2R
R
LINEAR INTEGRATED CIRCUIT
1V
Current Sense Comparator
Peak current (Is) determined by the formula: Ismax=10V/Rs.
A small RC filter be required to suppress switch transients.
SLOPE COMPENSATION
8
RT
4
CT
R1 R2
Isense
3
C
Rsense
A fraction of the oscillator ramp can be resistively summed with the current sense signal to provide slope
compensation for converts requiring duty cycles over 50%.Note that capacitor C, forms a filter with R2 to suppress
the leading edge switch spikes.
OSCILLATOR SECTION
Large RT
8
Small CT
RT
4
5
CT Small RT
Large CT
V4
INTERNAL CLOCK
V4
INTERNAL CLOCK
Dead time vs. CT(RT>5kΩ)
100
10
1
0.1 1
10
100
CT (nF)
Timing Resistance vs. Frequency
100
CT=2.2nF
CT=4.7nF
10
CT=10nF
CT=22nF
CT=47nF
CT=100nF
1
102 103 104 105 10 6
Frequency (Hz)
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
6 of 9
QW-R103-002,D
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