AD7866 Analog Devices, AD7866 Datasheet - Page 6

• Manufacturer Part Number: AD7866
• Description: Dual 1MSPS, 12-Bit, 2-Channel SAR ADC with Serial Interface
• Manufacturer: Analog Devices

Specifications of AD7866

• Resolution (bits): 12bit
• # Chan: 4
• Sample Rate: 1MSPS
• Interface: Ser,SPI
• Analog Input Type: SE-Uni
• Ain Range: Uni (Vref),Uni (Vref) x 2,Uni 2.5V,Uni 5.0V
• Adc Architecture: SAR
• Pkg Type: SOP

AD7866
Pin No.
1
2, 9
3, 8
4, 5
6, 7
10
Mnemonic
REF SELECT
D
AGND
V
V
V
B2
A2
REF
CAP
, V
, V
B, D
B1
A1
CAP
A
Function
Internal/External Reference Selection. Logic input. If this pin is tied to GND, the on-chip 2.5 V reference
is used as the reference source for both ADC A and ADC B. In addition, pins V
must be tied to decoupling capacitors. If the REF SELECT pin is tied to a logic high, an external refer-
ence can be supplied to the AD7866 through the V
required on D
a logic low, an individual external reference can be applied to both ADC A and ADC B through pins
D
Decoupling capacitors are connected to these pins to decouple the reference buffer for each respective
ADC. The on-chip reference can be taken from these pins and applied externally to the rest of a system.
Depending on the polarity of the REF SELECT pin and the configuration of the V
pins can also be used to input a separate external reference to each ADC. The range of the external
reference is dependent on the analog input range selected. See the Reference Configuration
Options section.
Analog Ground. Ground reference point for all analog circuitry on the AD7866. All analog input signals
and any external reference signal should be referred to this AGND voltage. Both of these pins should
connect to the AGND plane of a system. The AGND and DGND voltages ideally should be at the
same potential and must not be more than 0.3 V apart, even on a transient basis.
Analog Inputs of ADC B. Single-ended analog input channels. The input range on each channel is 0 V
to V
Analog Inputs of ADC A. Single-ended analog input channels. The input range on each channel is 0 V
to V
Reference Decoupling and External Reference Selection. This pin is connected to the internal reference
and requires a decoupling capacitor. The nominal reference voltage is 2.5 V, which appears at the pin;
however, if the internal reference is to be used externally in a system, it must be taken from either the
D
applying an external ref
CAP
CAP
REF
REF
A and D
A or D
or a 2
or a 2
CAP
CAP
CAP
B pins. This pin is also used in conjunction with the REF SELECT pin when
PIN FUNCTION DESCRIPTIONS
V
V
B, respectively. See the Reference Configuration Options section.
A and D
REF
REF
REF SELECT
PIN CONFIGURATION
range depending on the polarity of the RANGE pin upon the falling edge of CS.
range depending on the polarity of the RANGE pin upon the falling edge of CS.
erence to the AD7866. See the REF SELECT pin description.
D
D
AGND
AGND
CAP
CAP
V
CAP
V
V
V
V
REF
B2
B1
A2
A1
B
A
B. However, if the V
10
1
2
3
4
5
6
7
8
9
(Not to Scale)
TOP VIEW
–6–
AD7866
20
19
18
17
16
15
14
13
12
11
A0
CS
SCLK
D
D
DGND
DV
AV
RANGE
V
DRIVE
OUT
OUT
DD
DD
B
A
REF
REF
pin is tied to AGND while REF SELECT is tied to
pin, in which case decoupling capacitors are
REF
, D
REF
CAP
pin, these
A, and D
REV. A
CAP
B