CMX469A
1200/2400/4800 Baud FFSK Modem
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Features:
Description
- 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:
1008MHz 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
- CMX469AD3 - 20-pin SOIC
- CMX469AE2 - 24-pin TSSOP
- 2.7 to 5.5 V
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, TSSOP and DIL packages.
Block Diagram
