GENERAL DESCRIPTION

The PCA1070 is a CMOS integrated circuit performing all speech and line interface functions in fully electronic telephone sets. The device requires a minimum of external components. The transmission parameters are programmable via the I2C-bus. This makes the IC adaptable to nearly all worldwide country requirements and to a various range of speech transducers, without changing the (few) external components.

FEATURES

• Line interface with:

– Voltage regulator with programmable DC voltage drop

– Programmable set impedance

– Output to control an external switching MOS transistor for pulse dialling

– Programmable DC voltage during pulse dialling

– Circuitry for short DC settling time

• Interface to peripheral circuits with:

– Supply for microcontroller and DTMF diallers

– Input to sense supply voltage of microcontroller and output for reset of microcontroller

– I2C-bus (programming of parameters, control of all logic signals)

– High impedance DTMF signal input

– Input for external oscillator signal with on-chip DC blocking

– Power-down via the I2C-bus

– Stabilized supply for electret microphone

• Microphone and DTMF amplifiers:

– Low-noise microphone preamplifier suitable for various types of microphones

– Symmetrical high impedance microphone preamplifier inputs

– Programmable gain for microphone and DTMF channels

– Sending mute via the I2C-bus to disable microphone amplifier and enable DTMF amplifier

– Sending mute also to be used as privacy switch

– Dynamic limiting (speech controlled) to prevent distortion of line signal and sidetone; programmable maximum sending level

• Receiving amplifier:

– Suitable for various types of earpieces (including piezo)

– Programmable gain and hearing protection level

– Receiving mute via the I2C-bus to disable receiving amplifier and enable DTMF confidence tone

– On-chip anti-sidetone circuit with programmable sidetone balance

– Confidence tone in the earpiece during DTMF dialling

• Facility to regulate parameters with line current:

– Value of DC line current (bit code) readable via the I2C-bus

– Line loss compensation with fully software programmable characteristics (control range, stop current) of microphone/earpiece/DTMF amplifiers

– Fully software programmable control of sidetone balance and DC voltage drop as a function of line length.

APPLICATIONS

• Wired telephony (basic till feature phones)

• Combi-terminals (e.g. telephone and answering machine or FAX)

• Modems and base units of cordless telephones.