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ADVANCE INFORMATION<br />
<strong>UAC</strong> <strong>357xB</strong><br />
2.9. Dual Microphone and Stereo Line Inputs<br />
Pins: ADCR, ADCL, MICINL, MICINR, MICBIAS,<br />
ADCREF<br />
The <strong>UAC</strong> <strong>357xB</strong> provides a 2-channel ADC. The A/D<br />
converters achieve a signal-to-noise ratio better than<br />
90 dB (typ.) and a bandwidth of 20 kHz (at f s =48 kHz).<br />
The ADCs can be used either for stereo line or dual<br />
microphone input. Mixed mode mic/line is possible<br />
also.<br />
2.9.1. Line Input<br />
Line signals can be coupled in a pseudo-differential<br />
way. This means an external ground reference can be<br />
coupled into pin ADCREF (AC-coupled).<br />
The input gain for the line input is programmable in the<br />
range of −3 dB to 19.5 dB. Table 2–3 shows the line<br />
input voltage versus gain setting and the input impedance<br />
(depends on gain setting) for full range ADC<br />
input (clipping level).<br />
Note: Coupling caps for ADCL, ADCR, ADCREF must<br />
be identical for optimum performance.<br />
Table 2–3: Line input levels<br />
Line Input<br />
Voltage<br />
[mVpp]<br />
3V Mode<br />
Line Input<br />
Voltage<br />
[mVpp]<br />
5V Mode<br />
Gain<br />
Setting [dB]<br />
3388 4517 −3 85<br />
2851 3801 −1.5 79<br />
2399 3198 0 73<br />
2018 2691 1.5 67<br />
1698 2264 3 61<br />
1429 1905 4.5 55<br />
1202 1603 6 49<br />
1011 1349 7.5 44<br />
851 1135 9 39<br />
716 955 10.5 34<br />
602 803 12 30<br />
507 676 13.5 26<br />
427 569 15 23<br />
Input<br />
Impedance<br />
[kΩ]<br />
359 478 16.5 19<br />
302 403 17 17<br />
254 339 19.5 14<br />
Micronas Aug. 20, 2004; 6251-650-1AI 13
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