[AK4145]

MS0982-E-01

2010/09

- 13 -

The AK4145 is designed to be 100% modulation of L+R signal when L=R= 50% (approx. -6dBFS) signal data is input. In

addition to this -6dBFS, the BTSC standard contains the pre-emphasis filter. To prevent the clipping in a BTSC encoder

of the AK4145, following maximum input levels are recommended. The input data can be attenuated by controlling the

Stereo Volume Control registers (L7-0, R7-0 bits).

Frequency[Hz]

Maximum Input Level

to BTSC Encoder[dBFS]

20~1000

-7

2500

-10

5000

-14

8000

-15

13000

-22

Table 7. Maximum Input Level to BTSC Encoder

The AK4145 has a stereo digital volume control (DVOL. 256 levels, 0.5dB step, Mute). The L7-0, R7-0 bits control the

gain. The gain ranges from +31.0dB to –96.0dB, or MUTE. When the VOLC bit = “1” (default), the L7-0 bits control gain

for both Lch and Rch. When the VOLC bit = “0”, the L7-0 bits control gain for Lch and R7-0 bits control gain for Rch.

This volume has a soft transition function. When changing levels, transitions are executed in soft changes; thus no

switching noise occurs during these transitions. The transition time of 1 level and all levels are shown in Table 8. In

parallel control mode, volume control is fixed to 0dB.

DVOL Transition Time

1 Level

0dB to -96dB

+31.0dB to -96dB

4LRCK

768LRCK

1016LRCK

Table 8. DVOL Transition Time

L7-0

Gain

00H

+31.0dB

01H

+30.5dB

:

:

3DH

+0.5dB

3EH

0dB

(default)

3FH

-0.5dB

:

FDH

-95.5dB

FEH

-96.0dB

FFH

MUTE (-

∞)

Table 9. Lch Digital Volume

R7-0

Gain

00H

+31.0dB

01H

+30.5dB

:

:

3DH

+0.5dB

3EH

0dB

(default)

3FH

-0.5dB

:

FDH

-95.5dB

FEH

-96.0dB

FFH

MUTE (-

∞)

Table 10. Rch Digital Volume