TSC2101-Audio Codec w/ Integrated Headphone Speaker Amp ...

www.ti.comSLAS392C− JUNE 2003 − REVISED SEPTEMBER 2004AUDIO DATA CONVERTERSThe TSC2101 includes a stereo audio DAC and a mono audio ADC. Both ADC and DAC can operate with amaximum sampling rate of 53 kHz and support all audio standard rates of 8 kHz, 11.025 kHz, 12 kHz, 16 kHz,22.05 kHz, 24 kHz, 32 kHz, 44.1 kHz, and 48 kHz. By utilizing the flexible clock generation capability and internalprogrammable interpolation, a wide variety of sampling rates up to 53 kHz can be obtained from many possibleMCLK inputs. In addition, the DAC and ADC can independently operate at different sampling rates as indicatedin control register 00H/page 2.When the ADC or DAC is operating, the TSC2101 requires an applied audio MCLK input. The user should alsoset bit D13 of control register 06H/page 2 to indicate which Fsref rate is being used. If the codec ADC or DACis powered up, then the touch screen ADC uses MCLK and BCLK for its internal clocking, and the internaloscillator is powered down to save power.Typical audio DACs can suffer from poor out-of-band noise performance when operated at low sampling rates,such as 8 kHz or 11.025 kHz. The TSC2101 includes programmable interpolation circuitry to provide improvedaudio performance at such low sampling rates, by first upsampling low-rate data to a higher rate, filtering toreduce audible images, and then passing the data to the internal DAC, which is actually operating at the Fsrefrate. This programmable interpolation is determined using bit D5D3 of control register 00H/page 2.For example, if playback of 11.025 kHz data is required, the TSC2101 can be configured such that Fsref = 44.1kHz. Then using bit D5D3 of control register/page 2, the DAC sampling rate (Fs) can be set to Fsref/4, or FS= 11.025 kHz. In operation, the 11.025 kHz digital input data is received by the TSC2101, upsampled to 44.1kHz, and filtered for images. It is then provided to the audio DAC operating at 44.1 kHz for playback. In reality,the audio DAC further upsamples the 44.1 kHz data by a ratio of 128 x and performs extensive interpolationfiltering and processing on this data before conversion to a stereo analog output signal.Phase Locked Loop (PLL)The TSC2101 has an on chip PLL to generate the needed internal ADC and DAC operational clocks from awide variety of clocks that may be available in the system. The PLL supports an MCLK varying from 2 MHz to100 MHz and is register programmable to enable generation of required sampling rates with fine precision.ADC and DAC sampling rates are given byDAC_Fs FsrefN1andADC_Fs FsrefN2Where, Fsref must fall between 39 kHz and 53 kHz, and N1, N2=1, 1.5, 2, 3, 4, 5, 5.5, 6 are registerprogrammable.The PLL can be enabled or disabled using register programming. When PLL is disabledFsref MCLK128 QQ = 2, 3…17— Note: For ADC, with N2 = 1.5 or 5.5, odd values of Q are not allowed.— In this mode, the MCLK can operate up to 100 MHz, and Fsref should fall between 39 kHzand 53 kHz.When PLL is enabled21