IRIG-B AM DECODE CIRCUIT

Hi, armcc .

Since your input is up to 12V, I highly suggest that you should attenuate your signal to the necessary input voltage of the ADC. For LTC1401, you should attenuate your input to 2.048V. But I am just curious why you have opted in LTC1401? You can try looking into AD4056 Datasheet and Product Info | Analog Devices. This is our new device and a much recommended for newer designs. It has the same resolution; though, its throughput rate is 500 ksps, which is higher compared to LTC1401. 

Going back to the attenuation configuration, here is a tool that could help you in designing your signal chain: Signal Chain Designer | Precision Studio | Analog Devices. If you try doing the configuration in the signal chain designer, you will notice that the feedback resistor has a lower value.

For an optimal RC computation for its analog front-end section, you may use this documentation as your reference: Front-End Amplifier and RC Filter Design for a Precision SAR Analog-to-Digital Converter | Analog Devices. You can use the 100 mV droop voltage for your kickback calculation. Using this as your starting point, you can calculate its Ntau or number of time constant. Using also the droop voltage, you can also calculate its Cfilter. This will lead you in calculating the necessary Rfilter. 

Warm regards,
Jo