SM5950AM

NIPPON PRECISION CIRCUITS INC.—12

Sample Rate Conversion

The input/output sample rate conversion ratio is variable over a range 0.45 to 2.205 times frequency. The input

sample rate (fsi) range is 20kHz to 100kHz, while the output sample rate (fso) range is 30kHz to 50kHz. Note

that the sample rate conversion ratio lower limit means that conversion from fsi = 96kHz to fso = 32kHz is not

possible.

Anti-aliasing filter selection

The following 6 filters are provided to function as anti-aliasing filters during sample rate conversion, where the

optimum anti-aliasing filter is automatically selected in response to the automatic measurement of the sample

conversion ratio between the input sampling frequency (on LRCI) and the output sampling frequency (calcu-

lated using SCKO as reference).

If the selected anti-aliasing filter fs conversion ratio and the actual sample rate conversion ratio do not match,

the following phenomena occur.

If the fs conversion ratio is not fixed, the conversion will slowly follow the change in ratio, but in the process

the possibility exists that noise may occur in the audio data output.

Filter mode

fs conversion ratio (fso/fsi)

Selects range

Conversion frequency

(example)

1

1.0 to 2.205 times

≥ 0.969697 times

Up conversion

2

0.91875 times

0.864865 to 0.969697 times

48.0

→ 44.1

3

0.72562 times

0.711111 to 0.864865 times

44.1

→ 32.0

4

0.66667 times

0.627451 to 0.711111 times

48.0

→ 32.0

5

0.50000 times

0.492308 to 0.627451 times

96.0

→ 48.0

6

0.459375 times

≤ 0.492308 times

96.0

→ 44.1

Conversion condition

Response generated

Actual sample rate conversion ratio is lower than the

selected filter conversion ratio.

High-frequency aliasing noise occurs in the audio band.

Actual sample rate conversion ratio is higher than the

selected filter conversion ratio.

Primarily cuts high-frequency components in the audio

band.