TLC32040C Datasheet, PDF (17/33 Pages) Texas Instruments – ANALOG INTERFACE CIRCUITS

TLC32040C, TLC32040I, TLC32041C, TLC32041I
ANALOG INTERFACE CIRCUITS
SLAS014E – SEPTEMBER 1987 – REVISED MAY 1995
(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 3. (sin x)/x Roll-Off
fs (Hz)
7200
8000
9600
14400
19200
20 log _{sin π f/fs}
π f/fs
(f = 3000 Hz)
(dB)
– 2.64
– 2.11
– 1.44
– 0.63
– 0.35
The actual AIC (sin x) / x roll-off is 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) (u_{i + 1}) + p1 yi
where the constant p1 determines the pole locations.
The resulting squared magnitude transfer function is:
+ _* ^* _{ń )} |H(f)|²
p2² (1 p1)²
1 2p1 cos(2 p f f_s) p1²
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