CMX138 CML Microcircuits, CMX138 Datasheet - Page 10

• Manufacturer Part Number: CMX138
• Description: Audio Scrambler and Sub-Audio Signalling Processor
• Manufacturer: CML Microcircuits

Audio Scrambler and Sub-Audio Signalling Processor
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© 2008 CML Microsystems Plc
R5, R6, R7 and R8 should be selected to provide the desired dc gain of the microphone input.
If the DISC input is AC coupled, the selection of the coupling capacitor should allow for frequencies
from below 50Hz and up to 3kHz to be passed without significant distortion to allow both Audio and
sub-audio decoders to function within their specification.
If the MIC input is AC coupled, the selection of the coupling capacitor should allow for frequencies
from 300Hz and up to 3kHz to be passed without significant distortion to allow the audio filtering and
processing to function within their specification.
The gain should be such that the resultant output at the MICFB pin is within the microphone input
signal range specified in 7.11.1.
additional external gain stage may be required. C6 and C7 should be chosen to maintain a flat low
pass response up to 3kHz.
If a single-ended Microphone is used, then R6 should be connected to V
R1 and C1 should be chosen to maintain a flat low pass response up to 3kHz.
R9 and C8 should be chosen to maintain a flat low pass response up to 3kHz.
For optimum performance with low signal microphones, an
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BIAS
and R5 deleted.
D/138_FI1.0/5
CMX138