LTC4220 View Datasheet(PDF) - Linear Technology
Part Name
Description
Manufacturer
LTC4220 Datasheet PDF : 36 Pages
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LTC4252-1/LTC4252-2
LTC4252A-1/LTC4252A-2
APPLICATIONS INFORMATION
–48RTN
RIN
3× 1.8k
1/4W EACH
–48RTN
(SHORT PIN)
R1
392k
1%
R2
30.1k
1%
1
DDIDNZ†13B**
VIN
8
OV
LTC4252A-1
PWRGD
2
9
UV
7
DRAIN
C1
10nF
10
TIMER
6
GATE
CT
3
0.68μF
SS
4
VEE SENSE
CSS
5
68nF
CIN
1μF
R3
5.1k
*
VOUT
RD 1M
R4
38.3k RG 10Ω
RC
10Ω
CC
10nF
R5 27Ω
– 48V
*MOC207 **DIODES, INC †RECOMMENDED FOR HARSH ENVIRONMENTS
+
CL
100μF
LOAD
EN
Q1
IRF530S
RS
0.02Ω
425212 F20
Figure 20. Circuit Breaker with Foldback Current Limit Application
–48RTN
–48RTN
(SHORT PIN)
R1
392k
1%
R2
30.1k
1%
– 48V
*MOC207
RIN
3× 1.8k
1/4W EACH
+
CL
100μF
LOAD
1
DDIDNZ†13B**
CIN
1μF
R3
5.1k
EN
VIN
8
OV
LTC4252A-1
PWRGD
2
9
UV
7
DRAIN
C1
10nF
*
RD 1M
10
TIMER
6
GATE
CT
3
0.68μF
SS
4
VEE SENSE
CSS
5
68nF
C3
330nF
25V
**DIODES, INC †RECOMMENDED FOR HARSH ENVIRONMENTS
VOUT
C2
10nF
100V
R4
1k
1% RG 10Ω
Q1
IRF530S
425212 F21
Figure 21. Inrush Control Without a Sense Resistor Application
At power-up, Q5 and Q8 are held off low by the SS pin
of the LTC4252; resistors R5 and R8 pull the SENSE pin
closed to VEE. VEE is connected to the power supply with
lower voltage through the body diodes Q2 or Q3 until Q2
or Q3 is turned on. This allows the LTC4252 to perform
a start-up cycle and ramp up the SS and GATE voltage.
As the SS voltage ramps up to 2.2V, it turns on Q5 and Q8
and pulls TIMER low through Q6 and Q9. The sense voltage
rises as current flows into R5 and R8 through resistors R3
and R6. The ACL amplifier of the LTC4252 servos the sense
voltage to about 100mV as the GATE voltage regulates Q2
and Q3. Current flows into R4, Q4 and R7, Q7 as Q2 and
Q3 turn on. The respective node voltages at the R3 and R4
connection and the R6 and R7 connection are always kept
equal to their respective sense voltages by the Q4 and Q2
VDS drop and the Q7 and Q3 VDS drop assuming the Q5
and Q8 VDS drop is negligible.
425212fd
31
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