LTC1540IS8#TR Linear Technology, LTC1540IS8#TR Datasheet - Page 8

• Manufacturer Part Number: LTC1540IS8#TR
• Description: IC COMPARATOR 2% VOLT REF 8SOIC
• Manufacturer: Linear Technology
• Type: with Voltage Referencer

Specifications of LTC1540IS8#TR

• Number Of Elements: 1
• Output Type: CMOS, TTL
• Voltage - Supply: 2 V ~ 11 V, ±1 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

LTC1540
3.3V Output Low Dropout Linear Regulator
The LTC1540 can be connected as a micropower (I
5.5µA at V
When the output is low, Q1 turns on, allowing current to
charge output capacitor C1. Local feedback formed by R4,
Q1 and Q2 creates a constant-current source from the 5V
input to C1. R4, R1 and Q2’s V
limiting in the case of an output short-circuit to ground. C2
reduces output ripple, while the R2-R3 feedback voltage
divider establishes the output voltage.
Auto Power-Off Source
Figure 8 shows the circuit for a 30mA power supply that
has a timed auto power-off function. The comparator
TYPICAL APPLICATIONS
8
Figure 7. 3.3V Output Low Dropout Linear Regulator
C3
3
4
5
6
IN
IN
HYST
REF
IN
+
–
= 5V) low dropout linear regulator (Figure 7).
GND
1
+
–
V
V
+
7
IN
= 5V
V
LTC1540
–
2
OUT
8
2N3906
1540 F07
BE
U
Q2
also provide current
R1
47k
750k
430k
1%
1%
R3
R2
R4
10Ω
Q1
TP0610L
C1
10µF
C2
2.2nF
Q
V
3.3V
OUT
=
output is the switched power supply output. With a 10mA
load, it typically provides a voltage of (V
whole circuit draws a mere 0.8µA of quiescent current with
V
50mV of hysteresis for the comparator, and sets the IN
voltage at 200mV. This gives an IN
approximately 150mV
The RC time constant determines the maximum power-on
time of the OUT pin before power down occurs. This period
can be approximated by:
The actual time will vary with both the leakage current of
the capacitor and the input current at the IN
BAT
t = 4.6RC (seconds)
= 5V. The three resistor voltage divider programs
432k
2M
121k
Figure 8. Auto Power-Off Switch Operates
on 0.8µA Quiescent Current
4
5
6
IN
HYST
REF
LTC1540
–
2
+
–
V
–
V
V
BAT
+
7
GND
1
OUT
1540 F08
IN
+
3
8
+
BAT
trip threshold of
(V
10mA
– 0.17V). The
C
MOMENTARY
SWITCH
+
BAT
pin.
– 0.17V)
sn1540 1540fas
R
–