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Pin Name
I/O
Function
VIN
I
Input terminal of the NORM channel of the ADC.
NORM
VIN
I
Input terminal of the AUX channel of the ADC.
AUX
Decouple
I
Ground reference of the NORM and AUX channels
for the ADC.
VOUT
O
Non-inverting output terminal of the differential
P
output amplifier from the DAC.
VOUT
O
Inverting output terminal of the differential output
N
amplifier from the DAC.
V
O
Buffered output voltage reference.
REF
REF_FILTER O
Voltage reference external bypass filter node.
V
Analog supply voltage.
CC
GND
Analog ground.
A
Table 8.1 Analog Interface Pin Definitions
The ADC PGA may be used to increase the signal level by +6 dB, +20
dB, or +26 dB. This selection is configured by bits 9 and 0 (IG1, IG0) of
the analog control register. Input signal level to the sigma-delta
modulator should not exceed the V
ADSP-21msp58/59 Data Sheet. Refer to "Analog Input" in the "Design
Considerations" section of this chapter for more information.
An offset may be added to the input of the ADC in order to move the
ADC's idle tones out of the 4.0 kHz speech band range. This is selected
by bit 10 of the analog control register. The added offset must be
removed by the ADC's high pass filter; therefore the high pass filter
must be inserted (not bypassed) when the offset is added.
8.2.2
ADC
The analog interface's ADC consists of a 4th-order analog sigma-delta
modulator, an anti-aliasing decimation filter, and a digital high pass
filter. The sigma-delta modulator noise-shapes the signal and produces
1-bit samples at a 1.0 MHz rate. This bit stream, which represents the
analog input signal, is fed to the anti-aliasing decimation filter.
Analog Interface
specification listed in the
INMAX
8
8 – 3
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