MF6CWM-50 National Semiconductor, MF6CWM-50 Datasheet - Page 18

• Manufacturer Part Number: MF6CWM-50
• Description: IC FILTER 6TH ORER SW CAP SO14
• Manufacturer: National Semiconductor

Specifications of MF6CWM-50

• Filter Type: Butterworth, Lowpass Switched Capacitor
• Frequency - Cutoff Or Center: 20kHz
• Number Of Filters: 1
• Max-order: 6th
• Voltage - Supply: 5 V ~ 14 V
• Mounting Type: *
• Package / Case: *
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *MF6CWM-50

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2.0 Designing with the MF6
f
2.5 ALIASING CONSIDERATIONS
Aliasing effects have to be taken into consideration when in-
put signal frequencies exceed half the sampling rate. For the
MF6 this equals half the clock frequency (f
put signal contains a component at a frequency higher than
half the clock frequency, as in Figure 19a , that component
will be “reflected” about f
low f
IN
FIGURE 17. MF6-50 Abrupt Clock Frequency Change
FIGURE 19. The phenomenon of aliasing in sampled-data systems. An input signal whose frequecy is greater than
= 1.5 kHz (scope time base = 2 ms/div)
one-half the sampling frequency will cause an output to appear at a frequency lower than one-half the sampling
CLK
/2 as in Figure 19b . If this component is within the
(a) Input Signal Spectrum
CLK
/2 into the frequency range be-
CLK
). When the in-
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(Continued)
frequency. In the MF6, f
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18
at f
(b) Output Signal Spectrum. Note that the input signal
s
/2 + f causes an output signal to appear at f
passband of the filter and of large enough amplitude it can
cause problems. Therefore if frequency components in the
input signal exceed f
being applied to the MF6 input. The necessary amount of at-
tenuation will vary depending on system requirements. In
critical applications the signal components above f
have to be attenuated at least to the filter’s residual noise
level. An example circuit is shown in Figure 20 using one of
the uncommitted Op-Amps available in the MF6.
FIGURE 18. MF6-50 Step Input Response, Vertical =
2V/div., Horizontal = 1 ms/div., f
s
f
CLK
.
CLK
/2 they must be attenuated before
CLK
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= 100 kHz
s
/2 − f.
CLK
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/2 will