TC9470FN Datasheet, PDF (10/19 Pages) Toshiba Semiconductor – Modulation DA Converter with Built-in 8-Times Oversampling Digital Filter/Dynamic Digital Bass Boost/Analog Filter

TC9470FN
6. DA Conversion Circuit
The IC incorporates a second-order Σ-∆ modulation DA converter for two channels (simultaneous output
type). The internal structure of this is shown in Figure 9.
X (Z)
Data
+
Z^−1
+
2
Limiter
−
Z^−1
Y (Z)
Q
Output data
(bit-stream 1-bit DA conversion data)
+
−
Second-order Σ-∆ converter: Y (Z) = X (Z) + (1 − Z^−1)² Q (Z)
Figure 9 Σ-∆ Modulation DA Converter
The Σ-∆ modulation clock has been designed to operate at 192 fs (when 384 fs). The noise shaping
characteristics are shown in Figure 10.
10dB
0
500 k
1M
Frequency (Hz)
Figure 10 Noise Shaping Characteristics
7. Data Output Circuit
The output circuit is equipped with a third-order analog low-pass filter. This enables direct analog
signals to be acquired from the IC’s RO (pin 5) and LO (pin 9) output pins.
PDM signals
RO (LO)
VR
Figure 11 Analog Filter Circuit
10
2002-02-27