SM5843AS1 datasheet(16/24 Pages) NPC

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SM5843A

×1

NIPPON PRECISION CIRCUITS—16

Attenuation operation

When an attenuation value DATT is set, the attenua-

tion changes smoothly from the current attenuation

level to the new level. The new attenuation data is

stored in the attenuation register while the current

attenuation data is stored in a temporary register. The

attenuation then changes smoothly by ramping

between the two register values, updating the tempo-

rary register with each step. If a new attenuation

value for DATT is set before the previous target

attenuation level is reached, the attenuation then

ramps toward the new attenuation level.

When MUTE is HIGH, the attenuation level is

−∞.

When MUTE goes LOW (muting OFF), the attenua-

tion level returns to that of the original value of

DATT.

System Clock (XTI, XTO, CKO, CKSLN)

Two system clock frequencies, 384fs and 256fs, can

be used. An external clock source can be input on

XTI, or a crystal oscillator can be constructed by

connecting a crystal between XTI and XTO. The

system clock is also buffered and then output on

CKO. The system clock frequency selection and the

internal clock frequency are shown in the following

table.

Figure 4. Attenuation and mute timing

DATT1

DATT2

DATT4

DATT3

(Gain)

Setting2

Setting3

−∞

MUTE

Setting4

Time

Setting1

Parameter

CKSL

HIGH

LOW

XTI input clock frequency (fXI = 1/tXI)

384fs

256fs

CKO clock frequency

384fs

256fs

Internal clock frequency (tSYS)2 × tXI

tXI

Figure 5. Clock generator circuit

CKSLN

XTI

XTO

CKO

1 / 2

Internal system clock

(192fs or 256fs)

to timing controller

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