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UC2842AD-TR View Datasheet(PDF) - Microsemi Corporation

Part Name
Description
Manufacturer
UC2842AD-TR
Microsemi
Microsemi Corporation Microsemi
UC2842AD-TR Datasheet PDF : 8 Pages
1 2 3 4 5 6 7 8
PRODUCT DATABOOK 1996/1997
UC184xA/284xA/384xA
CURRENT MODE PWM CONTROLLER
PR O D U C T I O N D ATA S H E E T
T Y P I C A L A P P L I C A T I O N C I R C U I T S (continued)
FIGURE 6. — SLOPE COMPENSATION
VCC
DC BUS
UCx84xA
7(12)
VO
5V
8(14)
RT
2N222A
RSLOPE
From VO
CT
4(7)
Ri
2(3)
Rd
CF
RF
1(1)
UVLO
2.5V
S
5V
R REF
VREF
GOOD LOGIC
INTERNAL
BIAS
OSCILLATOR
ERROR
AMP
2R
R
C.S.
COMP
1V
PWM
LATCH
5(9)
7(11)
Q1
6(10)
5(8)
R
3(5)
C
RS
Due to inherent instability of current mode converters running above 50% duty cycle, slope compensation should be added to either
the current sense pin or the error amplifier. Figure 6 shows a typical slope compensation technique.
4.7K
1K
ERROR AMP
ADJUST
4.7K
FIGURE 7. OPEN LOOP LABORATORY FIXTURE
2N2222
100K
5K
ISENSE
ADJUST
RT
UCx84xA
1 COMP
VREF 8
2 VFB
VCC 7
3 ISENSE
OUTPUT 6
4 RTCT
GROUND 5
A
0.1µF 0.1µF
1K
VREF
VCC
OUTPUT
GROUND
CT
High peak currents associated with capacitive loads necessitate careful grounding techniques. Timing and bypass capacitors should be
connected to pin 5 in a single point ground. The transistor and 5k potentiometer are used to sample the oscillator waveform and apply an
adjustable ramp to pin 3.
Copyright © 1995
Rev. 1.2a 10/25
7
 

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