Analog Devices ADuCM310 Hardware Reference Manual page 21

ADuCM310 Hardware Reference Manual
Differential Mode
The amplitude of the differential signal is the difference between the signals applied to the positive and negative AINx pins (that is,
AIN+ − AIN−). The maximum amplitude of the differential signal is, therefore, −V
common mode (CM). The common mode is the average of the two signals (AIN+ + AIN−)/2, and is, therefore, the voltage that the two
inputs are centered on. This results in the span of each input being CM ± V
varies with V . The voltage at the positive and negative AINx pins must be within the allowed input voltage range.
REF
The output coding is twos complement in fully differential mode, with
1 LSB = 2 V /65,536
REF
Or
2 × 2.5 V/65,536 = 76.29 µV
where V = 2.5 V.
REF
The ideal input/output transfer characteristic is shown in Figure 7.
ADCDATx[31:12]
0000 1111 1111 1111 1111
0000 1111 1111 1111 1110
0000 1111 1111 1111 1101
0000 1111 1111 1111 1100
0000 0000 0000 0000 0011
0000 0000 0000 0000 0010
0000 0000 0000 0000 0001
0000 0000 0000 0000 0000
0V 1LSB
Figure 6. ADC Transfer Function: Single-Ended Mode
ADCDATx[31:12]
0000 0000 1111 1111 1110
1LSB =
0000 0000 1111 1111 1100
0000 0000 1111 1111 1010
0000 0000 0000 0000 0010
0000 0000 0000 0000 0000
1111 1111 1111 1111 1110
1111 0000 0000 0000 0100
1111 0000 0000 0000 0010
1111 0000 0000 0000 0000
–V + 1LSB
REF
Figure 7. ADC Transfer Function: Differential Mode
Rev. C | Page 21 of 192
V
REF
1LSB =
65536
V
REF
VOLT AGE INPUT
to +V
REF REF
/2. This voltage must be set up externally, and its range
REF
2 × V
REF
65536
0LSB +V – 1LSB
REF
VOLTAGE INPUT (V + – V –)
IN IN
– 1LSB
p-p (2 × V ). This is regardless of the
REF
UG-549