XE3005 데이터 시트보기 (PDF) - Semtech Corporation

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XE3005

Low-Power Audio CODEC

Semtech Corporation 

XE3005/XE3006

ss

sck

mosi

1

0 0 A4 A3 A2 A1 A0 msb

lsb

request (write to address A(4:0))

write data D(7:0) to address A(4:0)

Figure 18: SPI signal timing in write mode

4 SANDMAN™ FUNCTION (XE3006)

The Sandman™ function analyzes the audio signals in the ADC and DAC. Its output signals indicate whether an audio

signal is present in the ADC or DAC or if the processed signal is just noise. The threshold or reference value between

noise and audio signal as well as the minimum duration of an audio signal is user-programmable through the SPI

interface. If the XE3006 CODEC is used in a system that includes a microcontroller, a DSP or an RF link, the outputs of

the Sandman™ Interface can be used to bring these devices into standby or sleep mode whenever no audio signal is

being processed. In this way, the Sandman™ function contributes to significant additional power savings on the system

level outside the XE3006 chip.

The Sandman™ Interface consists of 2 digital outputs:

• The SMAD detects whether the ADC processes an audio signal. The calculation is made with the digital data leaving

the ADC.

• The SMDA detects whether an audio signal is processed by the DAC. The calculation is made with the digital data

entering through the Audio Interface.

The Sandman™ Interface is implemented for the ADC and for the DAC in an identical way. It works with a set of 4 user-

defined parameters: off time, on-time, ADC-reference and DAC-reference. The on time and the off time are the same for

ADC and DAC. However, the reference values for the ADC and the DAC are adjusted separately, as indicated in the

table below.

Input parameters

Off-time1(7:0)

Off-time2(15:8)

On-time(7:0)

ADC_reference(7:0)

DAC_reference(7:0)

Register

L

M

N

O

P

Sandman ADC

X

X

X

X

-

Sandman DAC

X

X

X

-

X

The Sandman™ Interface (for the ADC as well as for the DAC) is configured with three parameters:

• Reference (7:0): Absolute value under which the signal is considered noise and above which the signal is

considered to be an audio signal. The Sandman™ function is disabled (SMAD or SMDA at logic 1) if this parameter

is zero. The ADC and the DAC have separate Reference values.

• Off-time (15:0): Time until power down. The number of sequential samples that have to be lower than the

Reference for the power down signal to become active. The Sandman™ function is disabled (SMAD or SMDA at

logic 1) if this parameter is zero. The ADC and DAC have one common Off-time value.

© Semtech 2005

www.semtech.com

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