AD7366_07 AD [Analog Devices], AD7366_07 Datasheet - Page 17

• Manufacturer Part Number: AD7366_07
• Description: True Bipolar Input, Dual 1 ?s, 12-/14-Bit, 2-Channel SAR ADCs
• Manufacturer: AD [Analog Devices]

The AD7366/AD7367 can handle true bipolar input voltages.
The analog input can be set to one of three ranges: ±10 V, ±5 V,
or 0 V to 10 V. The logic levels on Pin RANGE0 and Pin RANGE1
determine which input range is selected as outlined in Table 8.
These range bits should not be changed during the acquisition
time prior to a conversion, but can change at any other time.
Table 8. Analog Input Range Selection
RANGE1
0
0
1
1
The AD7366/AD7367 require V
high voltage analog input structures. These supplies must be
equal to or greater than ±11.5 V. See Table 7 for the require-
ments on these supplies. The AD7366/AD7367 require a low
voltage 4.75 V to 5.25 V AV
a 4.75 V to 5.25 V DV
to 5.25 V V
Channel selection is made via the ADDR pin as shown in
Table 9. The logic level on the ADDR pin is latched on the
rising edge of the BUSY signal for the next conversion, not
the one in progress. When power is first supplied to the
AD7366/AD7367 the default channel selection is V
Table 9. Channel Selection
ADDR
0
1
TRANSFER FUNCTION
The output coding of the AD7366/AD7367 is twos complement.
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. The ideal transfer charac-
teristic is shown in Figure 19.
V
DRIVE
IN
0
Figure 18. Equivalent Analog Input Structure
supply for interface power.
RANGE0
0
1
0
1
Channels Selected
V
V
A1
A2
C1
CC
, V
, V
supply for digital power, and a 2.7 V
B1
B2
V
V
DD
SS
CC
D
D
supply to power the ADC core,
DD
and V
Range Selected
±10 V
±5 V
0 V to 10 V
Do not program
SS
R1
dual supplies for the
C2
A1
and V
B1
Rev. 0 | Page 17 of 28
.
Table 10. LSB Sizes for Each Analog Input Range
Input
Range
±10 V
±5 V
0 V to 10 V
Track-and-Hold
The track-and-hold on the analog input of the AD7366/AD7367
allows the ADC to accurately convert an input sine wave of full-
scale amplitude to 12-/14-bit accuracy. The input bandwidth of
the track-and-hold is greater than the Nyquist rate of the ADC.
The AD7366/AD7367 can handle frequencies up to 35 MHz.
The track-and-hold enters its tracking mode once the BUSY
signal goes low after the CS falling edge. The time required to
acquire an input signal depends on how quickly the sampling
capacitor is charged. With zero source impedance, 140 ns is suffi-
cient to acquire the signal to the 12-bit for the AD7366 and the
14-bit level for the AD7367. The acquisition time for the ±10 V,
±5 V, and 0 V to +10 V ranges to settle to within ±½ LSB is
typically 140 ns. The ADC goes back into hold mode on the
falling edge of
The acquisition time required is calculated using the following
formula:
where:
C is the sampling capacitance.
R is the resistance seen by the track-and-hold amplifier looking
at the input.
R
analog input.
SOURCE
t
ACQ
should include any extra source impedance on the
= 10 × ((R
011...111
011...110
000...001
000...000
111...111
100...010
100...001
100...000
Full-Scale
Range
20 V/4096
10 V/4096
10 V/4096
CNVST
–FSR/2 + 1LSB
Figure 19. Transfer Characteristic
SOURCE
AD7366
.
ANALOG INPUT
+ R) C)
LSB Size
(mV)
4.88
2.44
2.44
0V
+FSR/2 – 1LSB
AD7366/AD7367
Full-Scale
Range
20 V/16384
10 V/16384
10 V/16384
AD7367
LSB Size
(mV)
1.22
0.61
0.61