AD7367-5ARUZ AD [Analog Devices], AD7367-5ARUZ Datasheet - Page 18

• Manufacturer Part Number: AD7367-5ARUZ
• Description: 1 MSPS, 8-Channel, Software-Selectable, True Bipolar Input, 12-Bit Plus Sign ADC
• Manufacturer: AD [Analog Devices]

AD7329
Figure 26 shows the differential configuration during the
acquisition phase. For the conversion phase, SW3 opens and
SW1 and SW2 move to Position B (see Figure
impedances of the source driving the V
match; otherwise, the two inputs have different settling times,
resulting in errors.
OUTPUT CODING
The AD7329 default output coding is set to twos complement.
The output coding is controlled by the coding bit in the control
register. To change the output coding to straight binary coding,
the coding bit in the control register must be set. When
operating in sequence mode, the output coding for each
channel in the sequence is the value written to the coding bit
during the last write to the control register.
TRANSFER FUNCTIONS
The designed code transitions occur at successive integer LSB
values (that is, 1 LSB, 2 LSB, and so on). The LSB size is
dependent on the analog input range selected.
Table 7. LSB Sizes for Each Analog Input Range
Input Range
±10 V
±5 V
±2.5 V
0 V to +10 V
Figure 26. ADC Differential Configuration During Acquisition Phase
Figure 27. ADC Differential Configuration During Conversion Phase
V
V
V
V
IN
IN
IN
IN
+
–
+
–
B
B
V
B
B
V
A
A
A
A
REF
REF
Full-Scale Range/8192 Codes
20 V
10 V
5 V
10 V
SW1
SW2
SW1
SW2
C
C
C
C
S
S
S
S
SW3
SW3
COMPARATOR
COMPARATOR
IN
+ and V
CAPACITIVE
CAPACITIVE
CAPACITIVE
CAPACITIVE
CONTROL
CONTROL
27
LOGIC
LOGIC
DAC
DAC
DAC
DAC
). The output
IN
− pins must
LSB Size
2.441 mV
1.22 mV
0.61 mV
1.22 mV
Rev. 0 | Page 18 of 40
The ideal transfer characteristic for the AD7329 when twos
complement coding is selected is shown in Figure 28. The ideal
transfer characteristic for the AD7329 when straight binary
coding is selected is shown in Figure 29.
ANALOG INPUT STRUCTURE
The analog inputs of the AD7329 can be configured as single-
ended, true differential, or pseudo differential via the control
register mode bits, as shown in Table 4 of the Registers section.
The AD7329 can accept true bipolar input signals. On power-
up, the analog inputs operate as eight single-ended analog input
channels. If true differential or pseudo differential is required, a
write to the control register is necessary after power-up to
change this configuration.
Figure 30 shows the equivalent analog input circuit of the
AD7329 in single-ended mode. Figure 31 shows the equivalent
analog input structure in differential mode. The two diodes
provide ESD protection for the analog inputs.
Figure 28. Twos Complement Transfer Characteristic (Bipolar Ranges)
Figure 29. Straight Binary Transfer Characteristic (Bipolar Ranges)
000 ... 001
000 ... 000
100 ... 010
100 ... 001
100 ... 000
000 ... 010
000 ... 001
000 ... 000
011 ... 110
111 ... 110
111 ... 000
011 ... 111
011 ... 111
111 ... 111
111 ... 111
–FSR/2 + 1LSB
AGND + 1LSB
Figure 30. Equivalent Analog Input Circuit (Single Ended)
V
IN
0
–FSR/2 + 1LSB
AGND + 1LSB
C1
AGND – 1LSB
V
V
DD
SS
D
D
ANALOG INPUT
ANALOG INPUT
MUX
OUT
+
+FSR/2 – 1LSB BIPOLAR RANGES
+FSR – 1LSB
+FSR/2 – 1LSB BIPOLAR RANGES
+FSR – 1LSB
C3
ADC
C4
IN
+
UNIPOLAR RANGE
UNIPOLAR RANGE
R1
C2