LX1555MY Microsemi Analog Mixed Signal Group, LX1555MY Datasheet - Page 17
LX1555MY
Manufacturer Part Number
LX1555MY
Description
IC PWM CURRENT MODE 8.4V 8DIP
Manufacturer
Microsemi Analog Mixed Signal Group
Datasheet
1.LX1554CM.pdf
(18 pages)
Specifications of LX1555MY
Pwm Type
Current Mode
Number Of Outputs
1
Frequency - Max
500kHz
Duty Cycle
48%
Voltage - Supply
11 V ~ 25 V
Buck
Yes
Boost
Yes
Flyback
Yes
Inverting
No
Doubler
No
Divider
No
Cuk
No
Isolated
Yes
Operating Temperature
-55°C ~ 125°C
Package / Case
8-DIP
Frequency-max
500kHz
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Copyright © 1994
Rev. 1.0b
From V
2N222A
R
R
d
i
Due to inherent instability of fixed frequency current mode converters running above 50% duty cycle, slope compensation should be
added to either the current sense pin or the error amplifier. Figure 34 shows a typical slope compensation technique. Pin numbers
inside parenthesis refer to 14-pin package.
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.
O
R
C
SLOPE
F
ERROR AMP
ADJUST
C
T
4.7K
4.7K
8(14)
R
R
1K
4(7)
2(3)
1(1)
T
F
ADJUST
100K
ERROR
2N2222
OSCILLATOR
AMP
I
5V
SENSE
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
2.5V
5K
U
LTRA
UVLO
P
-L
R O D U C T I O N
R
FIGURE 35. — OPEN LOOP LABORATORY FIXTURE
T
OW
2R
5(9)
R
S
FIGURE 34. — SLOPE COMPENSATION
1
2
3
4
TART
GOOD LOGIC
COMP
V
I
R
SENSE
S
LX155x
T
FB
C
R
1V
T
V
-U
REF
LX155x
P
REF
5V
C
URRENT
COMP
C.S.
C
GROUND
T
OUTPUT
V
V
D
REF
CC
, C
LATCH
PWM
A T A
8
7
6
5
URRENT
INTERNAL
BIAS
0.1µF
S
-M
H E E T
ODE
0.1µF
PWM
(continued)
A
7(12)
1K
7(11)
6(10)
5(8)
3(5)
V
CC
LX1552/3/4/5
C
R
DC BUS
V
V
OUTPUT
GROUND
R
REF
CC
Q1
S
V
O
17