Datasheet
11
Maxim Integrated
Micropower, Single-Supply, UCSP/SOT23
Comparator + Precision Reference ICs
MAX9038–MAX9043/
MAX9050–MAX9053
and
4) Select R2. In this example, we will choose 1kΩ.
5) Select V
HYS
. In this example, we will choose 50mV.
6) Solve for R1:
where R1 ≈ 100kΩ, V
TH
= 2.525V, and V
TL
= 2.475V.
Board Layout and Bypassing
Power-supply bypass capacitors are not typically need-
ed, but would be called for in cases where supply
impedance is high, supply leads are long, or excessive
noise is expected on the supply lines. Use 100nF
bypass capacitors under these conditions. Minimize
signal trace lengths to reduce stray capacitance.
Reference Output/Load Capacitance
The MAX9038/MAX9039/MAX904_/MAX905_ do not
require an output capacitor on REF for frequency stabil-
ity. They are stable for capacitive loads up to 4.7nF.
However, in applications where the load or the supply
can experience step changes, an output capacitor will
reduce the amount of overshoot (or undershoot) and
assist the circuit’s transient response. When an appli-
cation is not subject to transient conditions, the REF
capacitor can be omitted.
Biasing for Data Recovery
Digital data is often embedded into a bandwidth- and
amplitude-limited analog path. Recovering the data can
be difficult. Figure 2 compares the input signal to a
time-averaged version of itself. This self-biases the
threshold to the average input voltage for optimal noise
margin.
Even severe phase distortion is eliminated from the dig-
ital output signal. Be sure to choose R1 and C1 so that:
where f
CAR
is the fundamental carrier frequency of the
digital data stream.
f
1
2R1C1
CAR
>>
π
0 050 5
1000
1 1000
. =
+
⎛
⎝
⎜
⎞
⎠
⎟
R
VV
R
RR
HYS CC
=
+
⎛
⎝
⎜
⎞
⎠
⎟
2
12
V
R
RR
TL
=−
+
⎛
⎝
⎜
⎞
⎠
⎟
25 1
2
12
.
V
R
RR
TH
=+
+
⎛
⎝
⎜
⎞
⎠
⎟
25 25
2
12
..
MAX9038–MAX9043
MAX9050–MAX9053
OUT
IN+
IN-
10kΩ
0.1μF
V
CC
V
IN
V
EE
V
CC
Figure 2. Time Averaging of the Input Signal for Data Recovery