AK9223 Datasheet, PDF (11/16 Pages) Asahi Kasei Microsystems – Dual 1-Bit, 10MHz, 2nd-Order, Modulat

[AK9223]
■ Digital Filter
Digital data stream is output form the modulator. This data stream should be processed by a digital filter to
obtain an equivalent digital data to the analog input. Transfer function of the simple Sinc³ filter is shown
below.
1 − 𝑧^{−𝑂𝑆𝑅 3}
H(z) = ( _{1 − 𝑧−1} )
This filter provides the best output performance with a relatively low number of gates required for
implementation. All the characterizations in this datasheet are done using a Sinc³ filter (OSR = 256,
Output Word Width: 16 bits).
Figure 4 and Figure 5 show the filter characteristics. The location of the first notch is fDATA (=fMOD /
OSR). The -3dB point is located at half the Nyquist frequency or fDATA/4.
Figure 4. Sinc³ Frequency Characteristics (OSR=32)
Figure 5. Sinc³ Frequency Characteristics (OSR=256)
014010283-E-01
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2015/01