Analog Devices adsp-2100 Manual page 181

VIN and VIN
NORM
(nominally 2.5V) of the ADSP-21msp58/59, which allows the analog
interface to operate from a single supply. The input signal should be
ac-coupled with an external capacitor (C
by the input resistance of the analog input (VIN
and the desired cutoff frequency. The cutoff frequency should be less than
or equal to 30 Hz. The following equations should be used to determine
the values for R , C
1
should be greater than or equal to 0.027 µF, C
1
2π f R
C =
1 IN
2
R = input resistance of ADSP-21msp58/59 (200 kΩ)
IN
=cutoff frequency ≤ 30 Hz
f
1
1
2π f C
R =
2 2
1
≤ 2.2 kΩ
R
1
20 kHz < f < 40 kHz *
2
1
2π f R
C =
2 1
1
C = C
3 2
* If minimum (< 0.1 dB) rolloff at 4 kHz is desired, f
Analog Interface
are biased at the internal voltage reference
AUX
, and C : R should be less than or equal to 2.2 kΩ, C
1 2 1
). The value of C
2 2
, VIN
NORM
should be equal to C
3
should be set to 40 kHz.
2
is determined
), 200 kΩ,
AUX
2
.
2
8
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