The Tone Detector (MSDET) is a monolithic CMOS integrated circuit for processing analog signals before microcontroller operations. The MSDET contains an I and Q detector driven by a Voltage controlled oscillator. The center frequency of the tone detection is one-half of the VCO oscillating frequency. Center frequencies from 1 Hz to 100 kHz can be detected, and FSK decoded. The MSDET is an analog PLL with improved noise immunity when compared to a digital design.

By using the MSDET to demodulate and detect FSK or tones a slower, lower cost microcontroller can be used. This reduction in microcontroller clock rate also reduces the problems with RF emissions for FCC and CE approvals. The MSDET operates with a single supply voltage from 2.7 VDC to 5.5 VDC

The MSDET is superior to industry standard tone decoders in that control of chatter and bandwidth can be adjusted with external resistors or capacitors

The MSDET is available in a 16-pin SOIC (150 mil wide). Industrial temperature range (-40 to +85oC) is available.


  • Low Power Consumption:
  • Typically less than 2.0 mW at 2.7V
  • Analog PLL: Better noise immunity over simple DSP counter techniques


  • Satellite radio communications
  • Standard and non-standard tone detection
  • Standard and non-standard FSK demodulation
  • Caller ID demodulation
  • Bell 103, 202 or ITU V.21, V.23 demodulation