Datasheet

8
LTC1443/LTC1444/LTC1445
144345fc
V
–
. The reference accuracy is 1.5% from –40°C to 85°C.
It can source up to 200µA and sink up to 15µA with a 5V
supply. The reference can drive a bypass capacitor of up to
0.01µF without oscillation and by inserting a series resistor,
capacitance values up to 100µF can be used (Figure 1).
Figure 2 shows the resistor value required for different
capacitor values to achieve critical damping.
APPLICATIO S I FOR ATIO
WUUU
IN A
+
5
OUT
V
+
V
–
R1
10k
R3
430Ω
R2
2.4M
C1
1.0µF
IN A
–
HYST
REF
4
14
8
5V
TO 8V
LTC1443/44/45 • F03
LTC1445
3
9
2
–
+
Figure 3a. V
+
Glitching Test Circuit
Figure 3b. V
+
Glitching Response
Figure 4. Programmable Hysteresis
8
R2
HYST
REF
14
R1
LTC1443/44/45 • F04
LTC1445
9
I
REF
R1 =
V
HB
(2)(I
REF
)
R2 =
I
REF
V
HB
2
()
1.221V –
CAPACITOR VALUE (µF)
0.001
0.1
RESISTOR VALUE (kΩ)
10
1000
0.01 0.1 101
LTC1443/44/45 • F02
1
100
Figure 2. Damping Resistance vs Bypass Capacitor Value
LTC144X
V
–
REF
R1
C1
REFERENCE
OUTPUT
LTC1443/44/45 • F01
Figure 1. Damping the Reference Output
Bypassing the reference can help prevent false tripping of
the comparators by preventing glitches on the V
+
or the
reference output voltage. Figure 3 shows the bypassed
reference output with a square wave applied to the V
+
pin.
Resistors R1 and R2 set 10mV of hysteresis, while R3
damps the reference response. Note that the comparator
output doesn’t trip.
Hysteresis
Hysteresis can be added to the LTC1444/LTC1445 by
connecting a resistor (R1) between the REF and HYST
pins, and a second resistor (R2) from HYST to V
–
(Figure 4).
The difference between the upper and lower threshold volt-
ages or hysteresis voltage band (V
HB
) is equal to twice the
voltage difference between the REF and HYST pins. When
more hysteresis is added, the upper threshold increases the
same amount as the lower threshold decreases. The maxi-
mum voltage allowed between REF and HYST is 50mV,
LTC1443/1444/1445 • TA02
V
+
8V
5V
V
REF
OUT
2ms/DIV
2mV/DIV