AD7608 Analog Devices, AD7608 Datasheet - Page 11

• Manufacturer Part Number: AD7608
• Description: 8-Channel DAS with 18-Bit, Bipolar, Simultaneous Sampling ADC
• Manufacturer: Analog Devices

Specifications of AD7608

• Resolution (bits): 18bit
• # Chan: 8
• Sample Rate: 200kSPS
• Interface: Par,Ser,SPI
• Analog Input Type: Diff-Bip
• Ain Range: Bip 10V,Bip 5.0V
• Adc Architecture: SAR
• Pkg Type: QFP

Data Sheet
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
Table 6. Pin Function Descriptions
Pin No.
1, 37, 38, 48
2, 26, 35,
40, 41, 47
5, 4, 3
6
7
8
9, 10
Type
P
P
DI
DI
DI
DI
DI
1 2 F 1 1 F
1
ANALOG INPUT
DECOUPLING CAPACITOR PIN
POWER SUPPLY
GROUND PIN
DATA OUTPUT
DIGITAL OUTPUT
DIGITAL INPUT
REFERENCE INPUT/OUTPUT
Mnemonic
AV
AGND
OS [2: 0]
P AR
A A
S TBY
A A
RANGE
CONVST A,
CONVST B
CC
/ SER SEL
E E
A A
E E
Description
Analog Supply Voltage 4.75 V to 5.25 V. This supply voltage is applied to the internal front-end
amplifiers and to the ADC core. These supply pins should be decoupled to AGND.
Analog Ground. This pin is the ground reference point for all analog circuitry on the AD7608. All
analog input signals and external reference signals should be referred to these pins. All six of these
AGND pins should connect to the AGND plane of a system.
Oversampling Mode Pins. Logic inputs. These inputs are used to select the oversampling ratio. OS 2
is the MSB control bit, while OS 0 is the LSB control bit. See the Digital Filter section for further
details on the oversampling mode of operation and Table 8 for oversampling bit decoding.
Parallel/Serial Interface Selection Input. Logic input. If this pin is tied to a logic low, the parallel
interface is selected. If this pin is tied to a logic high, the serial interface is selected. In serial mode,
the
serial data outputs. When the serial interface is selected, DB[15:9] and DB[6:0] pins should be tied to
GND.
Standby Mode Input. This pin is used to place the AD7608 into one of two power-down modes: standby
mode or shutdown mode. The power-down mode entered depends on the state of the RANGE pin
as shown in Table 7. When in standby mode, all circuitry, except the on-chip reference regulators,
and regulator buffers, is powered down. When in shutdown mode, all circuitry is powered down.
Analog Input Range Selection. Logic input. The polarity on this pin determines the input range of
the analog input channels. If this pin is tied to a logic high, the analog input range is ±10 V for all
channels. If this pin is tied to a logic low, the analog input range is ±5 V for all channels. A logic
change on this pin has an immediate effect on the analog input range. Changing this pin during
a conversion is not recommended. See the Analog Input section for more details.
Conversion Start Input A, Conversion Start Input B. Logic inputs. These logic inputs are used to
initiate conversions on the analog input channels. For simultaneous sampling of all input channels,
CONVST A and CONVST B can be shorted together and a single convert start signal applied.
Alternatively, CONVST A can be used to initiate simultaneous sampling for V1, V2, V3, and V4, and
CONVST B can be used to initiate simultaneous sampling on the other analog inputs (V5, V6, V7, and
V8). This is only possible when oversampling is not switched on.
When the CONVST A or CONVST B pin transitions from low to high, the front-end track-and-hold
circuitry for their respective analog inputs is set to hold. This function allows a phase delay to be
created inherently between the sets of analog inputs.
R D
A A
PAR/SER SEL
/ SCLK pin functions as the serial clock input. The DB7/D
E E
A A
FRSTDATA
CONVST A
CONVST B
RD/SCLK
RANGE
RESET
AGND
BUSY
STBY
AV
OS 0
OS 1
OS 2
DB0
CS
CC 1
10
12
13
14
15
16
11
2
3
4
5
6
7
8
9
Figure 7. Pin Configuration
64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
Rev. A | Page 11 of 32
PIN 1
(Not to Scale)
AD7608
TOP VIEW
OUT
46
40
A and DB8/D
48
47
45
44
43
42
41
39
38
37
36
35
34
33
AV
AGND
REFGND
REFCAPB
REFCAPA
REFGND
REFIN/REFOUT
AGND
AGND
REGCAP
AV
AV
REGCAP
AGND
REF SELECT
DB15
CC
CC
CC
OUT
B pins function as
AD7608