TC9470FN

2002-02-27

13

10.2.1 Setting Mode 1

Serial setting mode 1 is enabled when D12 = “L”.

(1)

Digital attenuator

The digital attenuation command is enabled when D12 = L. The attenuation data can be set in

4096 different ways (coefficient: 12 bit, maximum attenuation: −72.245dB). The relationship with

the command’s output is shown below.

Table 9 Attenuation Data/Audio Data Output

Attenuation Data

AT [11:00]

Audio Output

FFFH

−0.000dB

FFEH

−0.002dB

FFBH

−0.004dB

···

···

C80H

−2.142dB

···

···

640H

−8.163dB

···

···

002H

−66.224dB

001H

−72.245dB

000H

−∞

001 (HEX) to FFE (HEX): The attenuation value is obtained with the following equation.

ATT = 20 ℓog (input data/4095) dB

Example: When the attenuation data is EA0H

ATT = 20 ℓog (4000/4095) dB = −0.204dB

If an input level is set to −48dB or less when it is set as the amount (−72.245dB) of the maximum

attenuation, the target effective attenuation data of digital attenuator of TC9470FN will be lost. The

output data is set to “0” when an input level is set to −48dB or less. An effective input level is

decided by the following formula.

Effective input data = −[120dB + Attenuation level (dB)]

10.2.2 Setting Mode 2

Serial setting mode 2 is enabled when D12 = “H” and D11 = “L”.

(1)

Digital de-emphasis filter

Controlled with EMP.

Table 10 Digital De-Emphasis Filter Setting

EMP

L

H

De-emphasis filter

OFF

ON