Datasheet

MAX195
16-Bit, 85ksps ADC with 10µA Shutdown
______________________________________________________________________________________ 23
Even better than oversampling and averaging is over-
sampling and digital filtering. Averaging is just a rough
(but computationally simple) type of digital filter. Finite
impulse response (and other) digital filter algorithms are
readily available, and are useful even with slow proces-
sors if the data rate is low or the data does not need to
be processed in real-time. When using averaging, be
sure to average an odd number of samples to avoid
small offset errors caused by asymmetrical rounding.
Whether simple averaging or more complex digital fil-
tering is used, the effect of oversampling is to spread
the noise across a wider bandwidth. Digital filtering or
averaging then eliminates the portion of this noise that
lies above the filter’s passband, leaving less noise in
the passband than if oversampling was not used. An
additional benefit of oversampling is that it simplifies
the design or choice of an anti-aliasing pre-filter for the
input. You can use a filter with a more gradual rolloff,
because the sample rate is much higher than the fre-
quency of interest.
CK
(2 x CLK)
J
Q
+5V
K
CLK
BP/UP/SHDN
CK
2 x CLK
1
/
2
74HC73
Q
(CLK)
J
(CLOCK SHUTDOWN)
MAX195
CLOCK SHUTDOWN
Figure 24. Circuit to Stop Free-Running Asynchronous CLK
-150
-130
-110
-90
0 5 10 20 25
40
-30
-50
-70
-10
FREQUENCY (kHz)
SIGNAL AMPLITUDE (dB)
15 30 35
f
IN
= 1kHz
f
S
= 85kHz
T
A
= +25°C
Figure 25. MAX195 FFT Plot