INTRODUCTION
The MC145540 ADPCM Codec is a single chip implementation of a PCM codec-filter and an ADPCM encoder/decoder, and therefore provides an efficient solution for applications requiring the digitization and compression of voiceband signals. This device is designed to operate over a wide voltage range, 2.7 to 5.25 V, and as such is ideal for battery powered as well as ac powered applications. The MC145540 ADPCM Codec also includes a serial control port and internal control and status registers that permit a microcontroller to exercise many built-in features.

FEATURES
Key features of the MC145540 ADPCM Codec include:
• Single 2.7 to 5.25 V Power Supply
• Typical 3 V Power Dissipation of 55 mW, Power Down of 0. 15 mW
• Differential Analog Circuit Design for Lowest Noise
• Complete Mu-Law and A-Law Companding PCM Codec/Filter
• ADPCM Transcoder for 64, 32, 24, and 16 kbps data rates
• Universal Programmable Dual Tone Generator
• Programmable Transmit Gain, Receive Gain, and Sidetone Gain
• Low Noise, High Gain, Three Terminal Input Operational Amplifier for Microphone Interface
• Push-Pull 300 Ω Power Drivers with External Gain Adjust for Receiver Interface
• Push-Pull 300 Ω Auxiliary Output Drivers for Ringer Interface
• Voltage Regulated Charge Pump to Power the Analog Circuitry in Low Voltage Applications
• Receive Side Noise Burst Detect Algorithm