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Moteur de recherche de fiches techniques de composants électroniques |
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Moteur de recherche de fiches techniques de composants électroniques |
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TDA1548TZ Fiches technique(PDF) 7 Page - NXP Semiconductors |
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TDA1548TZ Fiches technique(HTML) 7 Page - NXP Semiconductors |
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7 / 20 page  1995 Nov 15 7 Philips Semiconductors Product specification Bitstream continuous calibration filter-DAC with headphone driver and DSP TDA1548T Soft mute Soft mute is controlled by MUTE (pin 16). When the input is active HIGH the value of the sample is decreased smoothly to zero following a raised cosine curve. 32 coefficients are used to step down the value of the data, each one being used 32 times before stepping on to the next. This amounts to a mute transition time of 23 ms at fs = 44.1 kHz. When MUTE is released (LOW), the samples are returned to the full level again following a raised cosine curve with the same coefficients being used in the reverse order. Mute is synchronized to the sample clock, so that the operation always takes place on complete samples. Digital sound processing features BASS BOOST A strong bass boost effect, which is useful in compensating for poor bass response of portable headphone sets, is implemented digitally in the TDA1548T and can be controlled by ADBB (pin 20) and AD3S (pin 22). Table 3 shows the bass boost values at different input voltages. Table 4 shows the selection mode status (flat/min/max) at different input voltages. Valid settings range from “flat” (no influence on audio) to +18 dB with step sizes of 2 dB in “minimum” and to +24 dB with step sizes of 2 dB in “maximum”. The programmable bass boost filter is a second-order shelving type with a fixed corner frequency of 130 Hz for the “minimum” setting and a fixed corner frequency of 230 Hz for the “maximum” setting and has a Butterworth characteristic. Because of the exceptional amount of programmable gain, bass boost should be used in conjunction with adequate prior attenuation, using the volume control. TREBLE A treble effect is implemented digitally in the TDA1548T and can be controlled by ADTR (pin 19) and AD3S (pin 22). Table 3 shows the treble values at different input voltages. Table 4 shows the selection mode status (flat/min/max) at different input voltages. Valid settings range from “flat” (no influence on audio) to +6 dB with step sizes of 2 dB in “minimum” and to +6 dB with a step size of 2 dB in “maximum”. The programmable treble filter is a first-order shelving type with a fixed corner frequency of 2.8 kHz for the “minimum” setting and a fixed corner frequency of 5.0 kHz for the “maximum” setting. DE-EMPHASIS De-emphasis is controlled by DEEM (pin 15). The digital de-emphasis filter is dimensioned to produce the de-emphasis frequency characteristics for the sample rate 44.1 kHz. With its 18-bit dynamic range, the digital de-emphasis of the TDA1548T is a convenient and component-saving alternative to analog de-emphasis. When the DEEM pin is active HIGH, de-emphasis is enabled. De-emphasis is synchronized to the sample clock, so that operation always takes place on complete samples. Oversampling filter and noise shaper The digital filter is a four times oversampling filter. It consists of two sections which each increase the sample rate by 2. The second order noise shaper operates at 64fs. It shifts in-band quantization noise to frequencies well above the audio band. This noise shaping technique, used in combination with a sign-magnitude coding, enables high signal-to-noise ratios to be achieved. The noise shaper outputs a 5-bit PDM bitstream signal to the DAC. Continuous calibration DAC The dual 5-bit DAC uses the continuous calibration technique. This method, based on charge storage, involves exact duplication of a single reference current source. In the TDA1548T, 32 such current sources plus 1 spare source are continuously calibrated. The spare source is included to allow continuous converter operation. The DAC receives a 5-bit data bitstream from the noise shaper. This data is converted to a sign-magnitude code so that no current is switched to the output during digital silence (input 00000H). In this way very high signal-to-noise performance is achieved. Component-saving stereo headphone driver High precision, low-noise amplifiers together with the internal conversion resistors RCONV1 and RCONV2 convert the converter output current to a voltage capable of driving a line output or headphone. The voltage is available at VOL and VOR (0.64 V RMS typical). A major component saving feature of the TDA1548T is that no DC-blocking capacitors are needed in the application, despite the asymmetrical supply. The VCOM output, pin 2, is biased to the same voltage that the right and left channel voltage outputs are, Vref, and is capable of sinking the sum of left and right channel load currents. Therefore, connecting a load between one of the outputs and VCOM only gives rise to a negligible amount of DC current through the load. |
Numéro de pièce similaire - TDA1548TZ |
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Description similaire - TDA1548TZ |
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