CML - Wireless Data - CMX469A

The CMX469A is a single-chip CMOS LSI circuit which operates as a full-duplex pin-selectable 1200, 2400 or 4800 baud FFSK Modem.

The mark and space frequencies are 1200/1800, 1200/2400 and 2400/4800Hz respectively. Tone frequencies are phase continuous; transitions occur at the zero crossing point.
Employing a common Xtal oscillator with a choice of two clock frequencies (1.008MHz or 4.032MHz) to provide baud-rate, transmit frequencies, and Rx and Tx synchronisation, the transmitter and receiver operate entirely independently including individual section powersave functions. The CMX469A includes on-chip circuitry for Carrier Detect and Rx Clock recovery, both of which are made available as output pins. Rx, Tx and Carrier Detect paths each contain a bandpass filter to ensure the provision of optimum signal conditions both in the modem and for the Tx modulation circuitry.

The CMX469A demonstrates a high sensitivity and good bit-error-rate under adverse signal conditions; the carrier detect time constant is set by an external capacitor, whose value should be arranged as required to further enhance this product’s performance in high noise environments. This low-power device requires few external components and is available in small outline plastic SOIC and TSSOP packages.

Block Diagram


  • Selectable Data Rates: 1200/2400/4800 Baud
  • Full Duplex FFSK
  • Rx and Tx Bandpass Filters
  • Clock Recovery and Carrier Detect Facilities
  • Pin Selectable Xtal/Clock Inputs:
  • 1.008MHz or 4.032MHz
  • Simple Control: No µP Required


  • Data-Over-Radio
  • PMR and Cellular Radio Signalling
  • Automatic Vehicle Location (Differential GPS) Links
  • Portable Data Terminals
  • Personal/Cordless Telephone
  • Industrial Control Signalling

Supply Requirement:

  • 2.7 to 5.5 V