75T204-IP Ver la hoja de datos (PDF) - TDK Corporation
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75T204-IP Datasheet PDF : 9 Pages
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75T204
5V Low-Power Subscriber
DTMF Receiver
APPLICATION INFORMATION
The 75T204 will tolerate total input RMS noise up to
12dB below the lowest amplitude tone. For most
telephone applications, the combination of the high
frequency attenuation of the telephone line and
internal band-limiting make special circuitry at the
input to the 75T204 unnecessary. However, noise
near the 56kHz internal sampling frequency will be
aliased (folded back) into the audio spectrum, so if
excessive noise is present above 28kHz, the simple
RC filter shown in Figure 5 may be employed to
band limit the incoming signal.
Noise will also be reduced by placing a grounded
trace around the XIN and XOUT pins on the circuit
board layout when using a crystal. It is important to
note that XOUT is not intended to drive an additional
device. XIN may be driven externally; in this case
leave XOUT floating.
NOISY
SIGNAL
2.4 k = 5%
ANALOG IN
75T204
0.01 mF = 20%
FIGURE 5: RC Filter
6
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