![](http://datasheet.mmic.net.cn/Linear-Technology/LTC1540IDD-TRPBF_datasheet_105391/LTC1540IDD-TRPBF_6.png)
6
LTC1540
sn1540 1540fas
APPLICATIONS INFORMATION
WU
U
V +
R1
430
R2
10k
C1
1F
5V
TO
8V
OUT
V –
21
7
8
GND
LTC1540
1540 F03a
IN+
IN–
HYST
REF
3
4
5
6
R3
2.4M
–
+
LTC1540
V –
REF
R1
C1
REFERENCE
OUTPUT
1540 F01
Figure 1. Damping the Reference Output
Figure 2. Damping Resistance vs Bypass Capacitor Value
Figure 3 shows the bypassed reference output with a
square wave applied to the V + pin. Resistors R2 and R3 set
10mV of hysteresis voltage band while R1 damps the
reference response. Note that the comparator output
doesn’t trip.
Low Voltage Operation: V + = 1.6V
The guaranteed minimum operating voltage is 2V (or
±1V). As the total supply voltage is reduced below 2V, the
performance degrades and the supply current falls. At low
supply voltages, the comparator’s output drive is reduced
and the propagation delay increases. The VREF and VOS are
also slightly worse. The useful input voltage range extends
from the negative supply to 0.9V below the positive
supply.
Test
your
prototype
over
the
full
temperature and supply voltage range if operation below
2V is anticipated. Because of the increase in supply
current, operation below 1.5V is not recommended
(Figure 4).
Figure 4. Supply Current vs Supply Voltage
SUPPLY VOLTAGE (V)
0
SUPPLY
CURRENT
(
A)
3
4
5
2.0
1540 F04
2
1
0
0.5
1.0
1.5
2.5
V – = GND = 0V
IN+ = 0V
IN– = REF = HYST
TA = 25°C
Figure 3a. Power Supply Transient Test Circuit
CAPACITOR VALUE (F)
0.001
0.1
RESISTOR
VALUE
(k
)
10
1000
0.01
0.1
10
1
1540 F02
1
100
Figure 3b. Power Supply Transient Rejection
2mV/
DIV
2ms/DIV
1540 F03b
8V
V +
5V
VREF
OUT