AD7691 Analog Devices, AD7691 Datasheet - Page 8

• Manufacturer Part Number: AD7691
• Manufacturer: Analog Devices

Specifications of AD7691

• Resolution (bits): 18bit
• # Chan: 1
• Sample Rate: 250kSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: (2Vref) p-p
• Adc Architecture: SAR
• Pkg Type: CSP,SOP

AD7691
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
Table 8. Pin Function Descriptions
Pin No.
1
2
3
4
5
6
7
8
9
10
1
AI = analog input, DI = digital input, DO = digital output, and P = power.
Mnemonic
REF
VDD
IN+
IN−
GND
CNV
SDO
SCK
SDI
VIO
EPAD
Figure 5. 10-Lead MSOP Pin Configuration
GND
VDD
REF
IN+
IN–
1
2
3
4
5
Type
AI
P
AI
AI
P
DI
DO
DI
DI
P
(Not to Scale)
AD7691
TOP VIEW
1
Description
Reference Input Voltage. The REF range is from 0.5 V to VDD. It is referred to the GND pin.
This pin should be decoupled closely to the pin with a 10 μF capacitor.
Power Supply.
Differential Positive Analog Input. Referenced to IN−. The input range for IN+ is between 0 V and V
centered about V
Differential Negative Analog Input. Referenced to IN+. The input range for IN− is between 0 V and V
centered about V
Power Supply Ground.
Convert Input. This input has multiple functions. On its leading edge, it initiates the conversions and
selects the interface mode of the part, either chain or CS mode. In CS mode, it enables the SDO pin when
low. In chain mode, the data should be read when CNV is high.
Serial Data Output. The conversion result is output on this pin. It is synchronized to SCK.
Serial Data Clock Input. When the part is selected, the conversion result is shifted out by this clock.
Serial Data Input. This input provides multiple features. It selects the interface mode of the ADC as follows:
Chain mode is selected if SDI is low during the CNV rising edge. In this mode, SDI is used as a data input to
daisy-chain the conversion results of two or more ADCs onto a single SDO line. The digital data level on
SDI is output on SDO with a delay of 18 SCK cycles.
CS mode is selected if SDI is high during the CNV rising edge. In this mode, either SDI or CNV can enable
the serial output signals when low, and if SDI or CNV is low when the conversion is complete, the busy
indicator feature is enabled.
Input/Output Interface Digital Power. Nominally at the same supply as the host interface
(1.8 V, 2.5 V, 3 V, or 5 V).
Exposed Pad. The exposed pad is not connected internally. For increased reliability of the solder joints, it is
recommended that the pad be soldered to the ground plane.
10
9
8
7
6
VIO
SDI
SCK
SDO
CNV
REF
REF
/2 and must be driven 180° out of phase with IN−.
/2 and must be driven 180° out of phase with IN+.
Rev. B | Page 8 of 28
NOTES
1. THE EXPOSED PAD IS NOT CONNECTED
Figure 6. 10-Lead QFN (LFCSP) Pin Configuration
INTERNALLY. FOR INCREASED RELIABILITY OF
THE SOLDER JOINTS, IT IS RECOMMENDED THAT
THE PAD BE SOLDERED TO THE GROUND PLANE.
GND
VDD
REF
IN+
IN–
1
2
3
4
5
(Not to Scale)
AD7691
TOP VIEW
10 VIO
9
8
7
6
SDI
SCK
SDO
CNV
REF
REF
,
,