Datasheet

14
LT1575/LT1577
TYPICAL APPLICATIONS N
U
Setting Output Voltage with the Adjustable LT1575
FB
1575 TA03
R2
V
OUT
= 1.21V(1 + R2/R1)
V
OUT
R1
Using “Sense-Less” Current Limit
C1
10µF
C
T
R3
10Ω
IPOSSHDN V
CC
1575 TA04
V
OUT
Q1
INEG
GATE
Shutdown Time-Out with Reset
Overvoltage Protection
R3
100k
R2
100k
C2*
1575 TA09
*C2 = 15µA(t)/1.11V
t = SHUTDOWN LATCH-OFF TIME
SHDN
Q2
2N3904
RESET
0V TO 5V
SHDN
1575 TA10
V
OUT
R5
R6
V
OUT(uth)
= 1.21(R6/R5) + 5µA(R6)
V
OUT(lth)
= 1.11(R6/R5) – 15µA(R6)
Shutdown Time-Out with Reset
Basic Thermal Shutdown
R1
100k
C1*
1575 TA07
*C1 = 15µA(t)/1.11V
t = SHUTDOWN LATCHOFF TIME
SHDN
Q1
VN2222L
RESET
0V TO 5V
SHDN
1575 TA08
RT1
10k
NTC
5V
R4
549Ω
RT1 = DALE NTHS-1206N02
THERMALLY MOUNT RT1
IN CLOSE PROXIMITY
TO THE EXTERNAL
N-CHANNEL MOSFET
Setting Current Limit
IPOS V
CC
R
SENSE
*
*I
LIM
= 50mV/R
SENSE

R
SENSE
= DISCRETE SHUNT RESISTOR OR
R
SENSE
= KELVIN-SENSED PC BOARD TRACE
ACTIVATING CURRENT LIMIT ALSO ACTIVATES
THE SHDN PIN TIMER
1575 TA05
V
OUT
Q2
INEG
GATE
Setting Current Limit with Foldback Limiting
IPOS V
CC
R4
D1
1N4148
D2
1N4148
R5
10Ω
1575 TA06
V
OUT
Q3
INEG
GATE
R6
1.2k