M41T00AUDD1E STMICROELECTRONICS [STMicroelectronics], M41T00AUDD1E Datasheet - Page 28

• Manufacturer Part Number: M41T00AUDD1E
• Description: Serial real-time clock with audio
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

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Audio section operation
The audio section is comprised of five main parts. The input includes a summing amplifier.
A minimum 10kΩ feedback resistor is required. With that and 20kΩ input resistors, the input
signals will be summed at unity gain.
An audio switch follows the amplifier. A tone, selectable between 256 and 512 Hz, can be
inserted into the audio stream in lieu of the input amplifier's output.
A low pass filter is next with a cut off of 8 kHz. To get a band pass with a 100 Hz low end,
the user should place an appropriate coupling capacitor at the input pin.