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XE3005I033TRLF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30P31-P33P34-P36P37-P37
© Semtech 2005 www.semtech.com
16
XE3005/XE3006
- Disable time (t
disable
) between the last rising edge of SCK and the rising edge of SS.
- SCK frequency (F
SCK
)
Delay Min Max Unit Comments
t
recover
125 - ns
t
disable
2 x T
master
- ns T
master
= clock period of the master clock MCLK
F
SCK
0.5 x F
master
Hz F
master
= frequency of the master clock MCLK
3.3.2 SPI Interface Modes
There are two SPI modes: read and write.
3.3.2.1 Read Mode
Read communication always takes place in pairs of bytes. A read request of 2 bytes is sent on the MOSI line. The
content of the addressed register, one byte, is dumped on the MISO line during the transmission of the second byte on
the MOSI. The formats of one byte are the following:
bit 7 6 5 4 3 2 1 0
mosi 1 1 0 msb A (4:0) lsb
bit 7 6 5 4 3 2 1 0
miso msb D(7:0) lsb
ss
sck
mosi
miso
request (read <address A(4:0)>)
read data D(7:0) of address A(4:0)
msb lsb
A1 0 1 1 A4 A2 A0 A3 1 1
0
Figure 17: SPI signal timing in read mode
3.3.2.2 Write Mode
Write communication always takes place in pairs of bytes. The format of the 2 bytes is:
Bit 7 6 5 4 3 2 1 0
mosi 1 0 0 msb A(4:0) lsb
Bit 7 6 5 4 3 2 1 0
mosi msb D(7:0) lsb
© Semtech 2005 www.semtech.com
17
XE3005/XE3006
ss
sck
mosi
request (write to address A(4:0))
write data D(7:0) to address A(4:0)
1 0 0
A4 A2
A1
A0 A3
msb
lsb
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 Register Sandman ADC Sandman DAC
Off-time1(7:0) L X X
Off-time2(15:8) M X X
On-time(7:0) N X X
ADC_reference(7:0) O X -
DAC_reference(7:0) P - 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
18
XE3005/XE3006
• 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.
All these parameters are set in the registers L, M, N, O and P.
Reference(7:0) On-time(7:0) Off-time(15:0) Sandman (SMAD or SMDA) Comments
0 don’t care don’t care logic 1 (disable function) Sandman disable
don’t care 0 don’t care logic 1 (disable function) Sandman disable
don’t care don’t care 0 logic 1 (disable function) Sandman disable
1.-.255
corresponds to
128.-.32640
1.-.255
corresponds to
50 µs – 12 ms
1 - 65535
corresponds to
50 µs - 3.2 sec
logic 1 (signal higher than ref)
logic 0 (signal lower than ref)
all registers ≠ zero
time for FSYNC =
20kHz
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:
• 16 bit inputs data (2’s-complement) : 0111’1111’1111’1111 = 0x7FFF max positive value
• 8 bit reference (unsigned) : 0111’1111’1000’0000 = 0xFF00/2 reference max
So the reference is compared to the 8 most significant bits of the absolute value of the input signal:
reference(7:0) Absolute reference AIN (mV) if gain = 4 AIN (mV) if gain = 20
0 0 0.00 0.00
1 128 1.10 0.27
2 256 2.20 0.55
M M M M
255
255 × 128 = 32640
280 70
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).
• 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).
In a first approximation, the following points are recommended:
• 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
min
= 10ms, (code = 200). f
min
is the minimum audio
frequency = 100Hz if FSYNC = 20kHz. The value of f
min
scales proportionally with the sampling frequency FSYNC. A
high-pass filter in the ADC filters out signals below 100Hz.
• Reference should be adjusted just above the noise level.
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XE3005I033TRLF

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IC CODEC LOW PWR 16BIT 20-TSSOP
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