CMX264D5

The CMX264D5 from CML Microcircuits is a frequency domain scrambler IC, specifically designed for use in analogue cellular phone systems. It ensures privacy through fixed or rolling code scrambling techniques, utilizing split band inversion. The device supports full duplex operation with separate Tx and Rx paths and includes a standby mode.

Key electrical characteristics include a low power operation with a voltage range of 2.7V to 3.75V, typically operating at 3.0V. It utilizes a 4.433619MHz crystal for operation and features a simple serial interface for microprocessor control. The IC is designed for high quality recovered audio and low current consumption.

Packaged in a low-height, surface-mount 24-SSOP (0.209", 5.30mm Width), the CMX264D5 is suitable for applications requiring compact designs. Its operating temperature range is -40°C to 85°C, making it robust for various environmental conditions. The scrambler is compatible with existing cellphone circuitry and is intended for communication systems.

This IC contains separate Tx and Rx paths for full duplex operation and operates under µProcessor control via a simple serial interface. In the Tx path, scrambling is achieved by splitting the audio band into two parts, or sub-bands, and frequency inverting each one. The frequency at which the signal is split, the “split-point”, can be either fixed or rolling between four possible settings resulting in a transmitted audio signal which is unintelligible to eavesdroppers.