TLC320AD545 Datasheet, PDF (13/37 Pages) Texas Instruments – Single Channel Data/Fax Codec

2 Functional Description
2.1 Device Requirements and System Overview
The TLC320AD545 device consists of single codec channel, a hybrid circuit with external resistors and capacitors
for setting gain and filter poles, serial port, and miscellaneous other logic functions.
2.2 Codec Functions
The codec portion of the device performs the functions for:
• One channel of analog-to-digital conversion
• Digital-to-analog conversion
• Lowpass filtering
• Control of analog input and output gains
• Internal oversampling coupled with internal decimation and interpolation
• A 16-bit serial port interface to the host processor.
The maximum sample rate is 11.025 kHz.
2.3 Hybrid Functions
The hybrid circuitry has integrated amplifiers whose gains and filter pole frequencies are set by external resistors and
capacitors. This allows maximum flexibility to make adjustments for board variations and international standards
while providing integration of the function. The filter amplifier stages are followed by a programmable gain amplifier,
which feeds an 8 Ω differential speaker driver for the AT41 call progress monitor speaker. The monitor speaker driver
can be programmed for 0 dB gain or muted through control register 2. The source for the monitor speaker input can
be chosen to be either the amplified DAC output (Data_Out PGA) or the ADC input signal through control register
1 (see Appendix A).
A 2.5 V/1.5 V reference voltage (DT_REF) is provided as a reference for the transformer. It is necessary to reference
to 2.5 V/1.5 V (rather than ground), since the amplifiers are powered off by single-rail supplies. DT_REF is 2.5 V when
DAV_DD is 5 V and 1.5 V when DAV_DD is 3.3 V.
2.4 Miscellaneous Logic and Other Circuitry
The logic functions include the circuitry required to implement serial port and control register programming through
secondary communication on those serial ports. Two control registers can be programmed during secondary
communications from the serial port. These control registers set amplifier gains, select loopback functions, and read
ADC overflow flags. In addition, a flash write enable (FWE) circuit takes an external logic input and provides current
to power the write enable circuit of an external memory device. The flash write enable circuit is powered from the
digital power supply.
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