XE3005 ETC, XE3005 Datasheet - Page 16

• Manufacturer Part Number: XE3005
• Description: (XE3005 / XE3006) Low-Power Audio CODEC
• Manufacturer: ETC

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 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.
The Sandman™ Interface (for the ADC as well as for the DAC) is configured with three parameters:
All these parameters are set in the registers L, M, N, O and P.
Reference(7:0)
16
corresponds to
128.-.32640
don’t care
don’t care
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.
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.
On-time (7:0): Time until wakeup. The number of sequential samples that have to be higher than the
Reference for the power down signal to become inactive. The Sandman™ function is disabled (SMAD or
SMDA at logic 1) if this parameter is zero. The ADC and DAC have one common On-time value.
1.-.255
0
ADC_reference(7:0)
DAC_reference(7:0)
Input parameters
Off-time2(15:8)
Off-time1(7:0)
On-time(7:0)
corresponds to
50 s – 12 ms
On-time(7:0)
don’t care
don’t care
1.-.255
0
1 - 65535
corresponds to
50 s - 3.2 sec
Off-time(15:0)
don’t care
don’t care
Register
0
M
N
O
P
L
Sandman (SMAD or SMDA)
logic 1 (disable function)
logic 1 (disable function)
logic 1 (disable function)
logic 1 (signal higher than ref)
logic 0 (signal lower than ref)
Sandman ADC
X
X
X
X
-
Sandman DAC
Data Sheet
XE3005/XE3006
Comments
Sandman disable
Sandman disable
Sandman disable
all registers
time for FSYNC =
20kHz
X
X
X
X
-
D0212-116
zero