MAX968EUA-T Maxim Integrated Products, MAX968EUA-T Datasheet - Page 11

• Manufacturer Part Number: MAX968EUA-T
• Description: Comparator ICs Quad, Micropower, Ul tra-Low-Voltage, Rai
• Manufacturer: Maxim Integrated Products

3) Calculate R1: R1 = (R3 + R4) x (V
4) Choose the trip point for V
5) Calculate R2 as follows:
6) Verify trip voltages and hysteresis as follows:
Power-supply bypass capacitors are not needed if sup-
ply impedance is low, but 100nF bypass capacitors
should be used when supply impedance is high or
when supply leads are long. Minimize signal lead
lengths to reduce stray capacitance between the input
and output that might cause instability.
R
R
2
2
Ultra-Low-Voltage, Rail-to-Rail I/O Comparators
in the values for this example, R1 = (2.2MΩ + 10kΩ)
x (50mV / 5.0V) = 22.1kΩ.
threshold voltage where the comparator output tran-
sitions from low to high as V
point. For this example, choose 3.0V.
where V
Choose a standard value of 15kΩ.
where V
is the falling-voltage trip point.
=
=
Hysteresis
V
V
V
V
IN
IN
THR
THF
⎛
⎜
⎝
⎛
⎜
⎝
1 2
V
REF
.
ri
falling
sin :
V
3 0
=
=
THR
x
.
THR
g
THR
x R
22
V
V
V
THR
REF
:
k
=
1
is the rising-voltage trip point, and V
Ω
⎞
⎟ −
⎠
is the rising-voltage trip threshold.
⎞
⎟ −
⎠
Circuit Layout and Bypassing
V
______________________________________________________________________________________
−
x R x
THR
1
R
⎛
⎜
⎝
1
22
1
1
R x V
R
1
1
k
−
−
3
1
Ω
⎛
⎜
⎝
+
V
R
R
THF
−
3
1
1
R
CC
+
4
1
+
2 2
.
R
⎞
⎟
⎠
IN
R
1
IN
M
2
4
Ω
rises above the trip
+
rising. This is the
1
HB
+
R
3
10
/ V
+
1
k
Ω
CC
R
Single/Dual/Quad, Micropower,
4
=
). Putting
⎞
⎟
⎠
14 76
.
THF
k
Ω
Figure 5 shows an application using the MAX965 as an
infrared receiver. The infrared photodiode creates a
current relative to the amount of infrared light present.
This current creates a voltage across R1. When this
voltage level crosses the reference voltage applied to
the inverting input, the output transitions. Optional R3
provides additional hysteresis for noise immunity.
Figure 6 shows an application using the MAX965
to convert a 2-cell voltage-level signal into a TTL-
compatible signal. The supply voltage for the compara-
tor comes from the 2-cell supply. The output is pulled
up to a 5V supply.
Figure 5. IR Receiver
Figure 6. 2-Cell to TTL Logic-Level Translator
2 CELLS
INPUT
V
CC
2-Cell to TTL Logic-Level Shifter
R
D
HYST
R3
REF
GND
0.1µF
V
V
CC
CC
HYST
REF
0.1µF
GND
V
CC
MAX965
MAX965
V
OUT
CC
IR Receiver
OUT
R
PULLUP
+5V
11