TSC2100_16 Datasheet, PDF (27/77 Pages) Texas Instruments – PROGRAMMABLE TOUCH SCREEN CONTROLLER WITH INTEGRATED

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TSC2100
SLAS378− NOVEMBER 2003
AUDIO DATA CONVERTERS
The TSC2100 includes a stereo audio DAC and a mono audio ADC. Both ADC and DAC can operate with a maximum
sampling rate of 53 kHz and support all audio standard rates of 8 kHz, 11.025 kHz, 12kHz, 16kHz, 22.05 kHz, 24 kHz,
32kHz, 44.1 kHz, and 48 kHz. By utilizing the flexible clock generation capability and internal programmable interpolation,
a wide variety of sampling rates up to 53 kHz can be obtained from many possible MCLK inputs. In addition, the DAC and
ADC can independently operate at different sampling rates as indicated in control register REG−00H/Page2.
When the ADC or DAC is operating, the TSC2100 requires an applied audio MCLK input. The user should also set
BIT−D13/REG−06H/Page2 to indicate which Fsref rate is being used. If the codec ADC or DAC is powered up, then the
touch screen ADC uses MCLK and BCLK for its internal clocking, and the internal oscillator 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 TSC2100 includes programmable interpolation circuitry to provide improved audio performance
at such low sampling rates, by first upsampling low-rate data to a higher rate, filtering to reduce audible images, and then
passing the data to the internal DAC, which is actually operating at the Fsref rate. This programmable interpolation is
determined using BIT−D5−D3/REG−00H/Page2.
For example, if playback of 11.025-kHz data is required, the TSC2100 can be configured such that Fsref = 44.1 kHz. Then
using BIT−D5−D3/REG−00H/Page2, 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 TSC2100, upsampled to 44.1 kHz, 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 interpolation filtering and processing on this data before conversion to a
stereo analog output signal.
PLL
The TSC2100 has an on-chip PLL to generate the needed internal ADC and DAC operational clocks from a wide variety
of clocks available in the system. The PLL supports an MCLK varying from 2 MHz to 50 MHz and is register programmable
to enable generation of required sampling rates with fine precision.
ADC and DAC sampling rates are given by
DAC_FS = Fsref/N1 and ADC_FS = Fsref/N2
where, Fsref must fall between 39 kHz and 53 kHz, and N1, N2 =1, 1.5, 2, 3, 4, 5, 5.5, 6 are register programmable.
The PLL can be enabled or disabled using register programming.
D When PLL is disabled
Fsref
+
MCLK
128 Q
Q = 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 50 MHz, and Fsref should fall within 32 kHz to 53 kHz.
D When PLL is enabled
Fsref
+
MCLK
2048
K
P
P = 1, 2, 3, …, 8
K = J.D
J = 1, 2, 3, ….,64
D = 0, 1, 2, …, 9999
P, J, and D are register programmable, where J is integer part of K before the decimal point, and D is four-digit fractional
part of K after the decimal point, including lagging zeros.
Examples:
If K = 8.5, Then J = 8, D = 5000
If K = 7.12, Then J = 7, D = 1200
If K = 7.012, Then J = 7, D = 120
The PLL is programmed through Registers 1BH and 1CH of Page2.
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