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TLC32044CFN Datasheet(PDF) 29 Page - Texas Instruments |
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TLC32044CFN Datasheet(HTML) 29 Page - Texas Instruments |
29 / 39 page ![]() sin π f/fs π f/fs TLC32044C, TLC32044E, TLC32044I, TLC32044M, TLC32045C, TLC32045I VOICE-BAND ANALOG INTERFACE CIRCUITS SLAS017F − MARCH 1988 − REVISED MAY 1995 29 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 (sin x) / x roll-off for a zero-order hold function The (sin x) / x roll-off for the AIC DAC zero-order hold function at a band-edge frequency of 3000 Hz for the various sampling rates is shown in the table below. Table 4. (sin x) / x Roll-Off 20 log fs (Hz) 20 log (f = 3000 Hz) fs (Hz) (f = 3000 Hz) (dB) s (f = 3000 Hz) (dB) 7200 − 2.64 8000 − 2.11 9600 − 1.44 14400 − 0.63 19200 − 0.35 The actual AIC (sin x)/ x roll-off will be slightly less than the above figures because the AIC has less than a 100% duty cycle hold interval. correction filter To compensate for the (sin x)/ x roll-off of the AIC, a first-order correction filter (shown below) is recommended. u(i + 1) (1 − p1)P2 + + z − 1 y(i + 1) p1 The difference equation for this correction filter is: yi + 1 = p2(1 − p1) (ui + 1) + p1 yi where the constant p1 determines the pole locations. The resulting squared magnitude transfer function is: p22 (1–p1)2 1 – 2p1 cos(2 p f fs) ) p12 |H(f)|2 + |
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