XE3005 ETC, XE3005 Datasheet - Page 17

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

The reference (7:0) value is related to the absolute value of the 16 bits input signal. The following format is used
for the comparison:
So the reference is compared to the 8 most significant bits of the absolute value of the input signal:
The values in this table are amplitude values, RMS values can be derived by dividing the numbers by 2.
The working mechanism of the Sandman™ function is the following:
The incoming data is compared to the reference after each time step (1/FSYNC = 50µs if FSYNC = 20kHz).
In a first approximation, the following points are recommended:
The CODEC bandwidth is around 100 Hz to 10 kHz at the nominal system frequency settings (MCLK = 5 MHz,
CKDIV = 1, FSYNC = 20 kHz).
In digital loop back mode, the data entering into the Audio Interface is not transferred to the DAC. However, the
Sandman™ function (if activated) continues to output the SMDA signal based on the data entered into the Audio
Interface (input terminal SDI).
17
16 bit inputs data (2’s-complement) : 0111’1111’1111’1111 = 0x7FFF
8 bit reference (unsigned)
During the On-time phase
If the input data is higher than the reference, a counter will be incremented otherwise the counter is reset.
When the counter reaches the On-time value, then the SMAD or SMDA signal is activated (high level).
During the Off-time phase
If the input data is lower than the reference, a counter will be incremented otherwise the counter is reset.
When the counter reaches the Off-time value, then the SMAD or SMDA signal is deactivated (low level).
On-time at least 1ms. If the On-time is shorter than 1 ms, the Sandman™ function becomes sensitive to
spikes in the audio input signal AIN.
Off-time at least 10ms, the Off-time should be longer than 1/f
audio frequency = 100Hz if FSYNC = 20kHz. The value of f
frequency FSYNC. A high-pass filter in the ADC filters out signals below 100Hz.
Reference should be adjusted just above the noise level.
reference(7:0)
255
0
1
2
M
Absolute reference
255
128 = 32640
128
256
0
M
: 0111’1111’1000’0000 = 0xFF00/2
AIN (mV) if gain = 4
0.00
1.10
2.20
280
M
min
min
= 10ms, (code = 200). f
scales proportionally with the sampling
max positive value
reference max
AIN (mV) if gain = 20
Data Sheet
XE3005/XE3006
0.00
0.27
0.55
70
M
min
is the minimum
D0212-116