TC9470FN Datasheet, PDF (7/19 Pages) Toshiba Semiconductor – Modulation DA Converter with Built-in 8-Times Oversampling Digital Filter/Dynamic Digital Bass Boost/Analog Filter

TC9470FN
The digitalization of the de-emphasis filter eliminates the need for such external components as resistors,
condensers and analog switches. In addition to this, the coefficients are aligned to reduce error in the
de-emphasis filter characteristics.
The filter structure and characteristics are shown below.
Input data
+
Z^−1
b₀ ⁺
a₁
b₁
Transfer
function
:
H (Z) =
(b₀ + b₁Z^-1)
(1- a₁Z^-1)
|G (j_ω)|
1_/T1 1_/T2
T₁ = 50 µs, T₂ = 15 µs
Figure 4 IIR Digital De-Emphasis Filter
Figure 5 Filter Characteristics
5. Dynamic Digital Bass Boost Circuit
ON/OFF for the dynamic digital bass boost is controlled in the parallel mode ( P/S = “H”) with the DBB1
pin (pin 20) and the DBB2 pin (pin 21).
This is set in the serial mode ( P/S = “L”) with a microcontroller or other equipment. (refer to 10.2
microcontroller setting mode for further details on serial mode settings.)
A block diagram for the dynamic bass boost circuit is shown in Figure 6.
INPUT
L.P.F
OUTPUT
+
SERIAL
ATTENUATOR
COMPRESSOR BLOCK
Coefficient length: 7 bits
Figure 6 Dynamic Digital Bass Boost Circuit Block
The compressor’s compression ratio when in the control mode for the parallel mode is shown below.
Table 3 Compressor Compression Ratio (when in the parallel mode)
DBB max
DBB MID
18dB
12dB
The compressor’s compression characteristics are as follows:
Table 4 Compressor Compression Characteristics (when in the parallel mode)
DBB max
DBB MID
−36dB
−24dB
7
2002-02-27