The TLC320AD55, a 16-bit analog interface circuit (AIC), is a versatile analog front end for business audio and voice over data applications. This includes personal digital assistants (PDAs), computer-related speech processing, teleconferencing, and V.34/ V.FAST class fax/modems. The 'AD55 also features a simple interface to the TMS320C5X and 'C2X families of DSPs.
The TLC320AD55 uses 64X oversampling for analog-to-digital conversion (ADC) and digital-to-analog conversion (DAC) to produce a cost-effective, high resolution, low-noise system. Advantages of sigma-delta converters are a higher dynamic range and signal-to-noise ratio than traditional converters due to oversampling and the noise-shaping characteristic of the modulator. The TLC320AD55 offers a typical dynamic range of 86 dB for the ADC channel and 80 dB for the DAC channel. It also offers a minimum signal-to-noise ratio (SNR) of 80 dB for the ADC channel and 74 dB for the DAC channel. Another major advantage is that due to the 64X oversampling, the TLC320AD55 requires only a single pole R-C for the anti-aliasing filter. This is due to the sample frequency being far enough away from the signal frequency band that a single pole gives adequate rejection.
The analog and digital loopback functions provide a means of testing the ADC and DAC channels and can be used for in-circuit system level tests. The loopbacks feed the appropriate output to the corresponding input on the IC. The 'AD55 features a fully programmable serial port interface whose options include 15 or 16 bit resolution, input port selection, bypassing of the interpolation or decimation filters, and programmable gain of the analog output amplifier. A power down mode reduces the power dissipation from the typical operating level of 150 mW to only 16 mW.
The TLC320AD55 is available in the 28-pin DW plastic small outline package.
Vol 13, September, 1995
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