SG2843DM Microsemi Analog Mixed Signal Group, SG2843DM Datasheet - Page 13

• Manufacturer Part Number: SG2843DM
• Description: IC PWM CURRENT MODE 8SOIC
• Manufacturer: Microsemi Analog Mixed Signal Group

Specifications of SG2843DM

• 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: Yes
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: Yes
• Operating Temperature: -25°C ~ 85°C
• Package / Case: 8-SOIC
• Frequency-max: 500kHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Copyright © 2000
Rev. 1.6a 10/04
From V
Due to inherent instability of current mode converters running above 50% duty cycle, a slope compensation should be added to
either current sense pin or the error amplifier. Figure 23 shows a typical slope compensation technique.
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.
2N222A
R
R
i
d
O
R
C
SLOPE
F
ERROR AMP
ADJUST
8(14)
R
R
4(7)
C
2(3)
1(1)
T
F
T
4.7K
4.7K
1K
ERROR
OSCILLATOR
AMP
5V
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
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
100K
2.5V
ADJUST
2N2222
I
SENSE
5K
C
UVLO
U R R E N T
P
FIGURE 24. — OPEN LOOP LABORATORY FIXTURE
R O D U C T I O N
2R
R
5(9)
T
R
FIGURE 23. — SLOPE COMPENSATION
SG1842/43
GOOD LOGIC
- M
1
2
3
4
S
R
1V
V
COMP
V
I
R
SENSE
REF
T
FB
C
O D E
T
SG1842/43
REF
5V
COMP
C.S.
P W M C
C
GROUND
T
OUTPUT
D
LATCH
PWM
V
V
A T A
REF
CC
8
7
6
5
O N T R O L L E R
INTERNAL
BIAS
5V
S
H E E T
0.1µF
SG1842/SG1843 Series
0.1µF
(continued)
7(12)
A
1K
7(11)
6(10)
5(8)
3(5)
V
CC
C
R
V
V
OUTPUT
GROUND
REF
CC
V
IN
Q1
R
S
V
O
13