Analog-to-Digital Converter. ADS8881 Datasheet

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ADS8881 Datasheet
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Part ADS8881
Description SAR Analog-to-Digital Converter
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ADS8881
SBAS547D – MAY 2013 – REVISED AUGUST 2015
ADS8881x 18-Bit, 1-MSPS, Serial Interface, microPower, Miniature,
True-Differential Input, SAR Analog-to-Digital Converter
1 Features
1 Sample Rate: 1 MHz
• No Latency Output
• Unipolar, True-Differential Input Range:
–VREF to +VREF
• Wide Common-Mode Voltage Range:
0 V to VREF with 90-dB CMRR (min)
• SPI™-Compatible Serial Interface with
Daisy-Chain Option
• Excellent AC and DC Performance:
– ADS8881C:
INL: ±1 LSB (typ), ±2.0 LSB (max)
DNL: ±1.0 LSB (max), 18-Bit NMC
SNR: 100 dB, THD: –115 dB
– ADS8881I:
INL: ±1.5 LSB (typ), ±3.0 LSB (max)
DNL: +1.5 and –1 LSB (max), 18-Bit NMC
SNR: 100 dB, THD: –115 dB
• Wide Operating Range:
– AVDD: 2.7 V to 3.6 V
– DVDD: 2.7 V to 3.6 V
(Independent of AVDD)
– REF: 2.5 V to 5 V (Independent of AVDD)
– Operating Temperature:
ADS8881C : 0°C to +70°C
ADS8881I : –40°C to +85°C
• Low-Power Dissipation:
– 5.5 mW at 1 MSPS
– 0.55 mW at 100 kSPS
– 55 µW at 10 kSPS
• Power-Down Current (AVDD): 50 nA
• Full-Scale Step Settling to 18 Bits: 290 ns
• Packages: MSOP-10 and VSON-10
2 Applications
• Automatic Test Equipment (ATE)
• Instrumentation and Process Controls
• Precision Medical Equipment
• Low-Power, Battery-Operated Instruments
3 Description
The ADS8881 is an 18-bit, 1-MSPS, true-differential
input, analog-to-digital converter (ADC). The device
operates with a 2.5-V to 5-V external reference,
offering a wide selection of signal ranges without
additional input signal scaling. The reference voltage
setting is independent of, and can exceed, the analog
supply voltage (AVDD).
The device offers an SPI-compatible serial interface
that also supports daisy-chain operation for
cascading multiple devices. An optional busy-
indicator bit makes synchronizing with the digital host
easy.
The device supports unipolar, true-differential analog
input signals with a differential input swing of –VREF to
VREF. This true-differential analog input structure
allows for a common-mode voltage of any value in
the range of 0 V to VREF (when both inputs are within
the operating input range of –0.1 V to VREF
+ 0.1 V).
Device operation is optimized for very low-power
operation. Power consumption directly scales with
speed. This feature makes the ADS8881 excellent for
lower-speed applications.
Device Information(1)
PART NUMBER
PACKAGE
BODY SIZE (NOM)
ADS8881x
VSSOP (10)
VSON (10)
3.00 mm × 3.00 mm
3.00 mm × 3.00 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Traditional Input Range
ADS8881 Input Range
0V
VDIFF
+VREF
-VREF
True-Differential Input Range
2.5 V to 5 V 2.7 V to 3.6 V
VREF
VCM
VREF
VCM
0V
VREF/2
0 V - VREF
0 V - VREF
AINP
AINM
REF
AVDD
DVDD
ADS8881
DIN
SCLK
DOUT
CONVST
GND
2.7 V to 3.6 V
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.



Texas Instruments ADS8881
ADS8881
SBAS547D – MAY 2013 – REVISED AUGUST 2015
www.ti.com
Table of Contents
1 Features .................................................................. 1
2 Applications ........................................................... 1
3 Description ............................................................. 1
4 Revision History..................................................... 2
5 Companion Products............................................. 4
6 Device Comparison ............................................... 5
7 Pin Configurations and Functions ....................... 6
8 Specifications......................................................... 7
8.1 Absolute Maximum Ratings ...................................... 7
8.2 ESD Ratings.............................................................. 7
8.3 Recommended Operating Conditions....................... 7
8.4 Thermal Information .................................................. 7
8.5 Electrical Characteristics........................................... 8
8.6 Timing Requirements: 3-Wire Operation ................ 10
8.7 Timing Requirements: 4-Wire Operation ................ 11
8.8 Timing Requirements: Daisy-Chain ........................ 12
8.9 Typical Characteristics ............................................ 13
9 Parametric Measurement Information ............... 20
9.1 Equivalent Circuits .................................................. 20
10 Detailed Description ........................................... 21
10.1 Overview ............................................................... 21
10.2 Functional Block Diagram ..................................... 21
10.3 Feature Description............................................... 21
10.4 Device Functional Modes...................................... 24
11 Application and Implementation........................ 33
11.1 Application Information.......................................... 33
11.2 Typical Applications .............................................. 36
12 Power-Supply Recommendations ..................... 45
12.1 Power-Supply Decoupling..................................... 45
12.2 Power Saving ........................................................ 45
13 Layout................................................................... 47
13.1 Layout Guidelines ................................................. 47
13.2 Layout Example .................................................... 47
14 Device and Documentation Support ................. 48
14.1 Device Support...................................................... 48
14.2 Documentation Support ........................................ 48
14.3 Receiving Notification of Documentation Updates 48
14.4 Community Resources.......................................... 48
14.5 Trademarks ........................................................... 49
14.6 Electrostatic Discharge Caution ............................ 49
14.7 Glossary ................................................................ 49
15 Mechanical, Packaging, and Orderable
Information ........................................................... 49
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision C (July 2014) to Revision D
Page
• Added Companion Products and Device Comparison sections............................................................................................. 4
• Changed ESD Ratings table to current standards, added HBM and CDM data ................................................................... 7
• Added timing specifications for different operating temperature ranges for the tconv, td-CK-DO, and tquiet parameters in
the Timing Requirements: 3-Wire Operation table .............................................................................................................. 10
• Added timing specifications for different operating temperature ranges for the tconv parameter in Timing
Requirements: 4-Wire Operation table ................................................................................................................................. 11
• Added timing specifications for different operating temperature ranges for the tconv parameter in Timing
Requirements: Daisy-Chain table ........................................................................................................................................ 12
2 Submit Documentation Feedback
Product Folder Links: ADS8881
Copyright © 2013–2015, Texas Instruments Incorporated



Texas Instruments ADS8881
www.ti.com
ADS8881
SBAS547D – MAY 2013 – REVISED AUGUST 2015
Changes from Revision B (December 2014) to Revision C
Page
• Changed format to meet latest data sheet standards; added new sections, moved existing sections ................................. 1
• Changed ADS8881 to ADS8881C, added ADS8881I ........................................................................................................... 1
• Separated ADS8881C and ADS8881I specifications in Excellent AC and DC Performance Features bullet ....................... 1
• Changed Device Information table to current standards ........................................................................................................ 1
• Added Recommended Operating Conditions table ................................................................................................................ 7
• Changed LSB footnote to include how to convert LSB to ppm ............................................................................................. 8
• Changed fSCLK parameter maximum specification from 66.6 MHz to 70 MHz in Timing Requirements: 3-Wire
Operation table. .................................................................................................................................................................... 10
• Changed tSCLK parameter minimum specification from 15 ns to 14.3 ns in Timing Requirements: 3-Wire Operation
table. ..................................................................................................................................................................................... 10
• Added more information about validity of data on SCLK edges in all interface modes ....................................................... 25
• Changed diagrams and text for better explanation of the daisy-chain feature in the Daisy-Chain Mode section ............... 30
• Changed Equation 2 and Equation 3 .................................................................................................................................. 34
• Added Layout Guidelines section ......................................................................................................................................... 47
Changes from Revision A (July 2013) to Revision B
Page
• Changed Wide Common-Mode Voltage Range Features bullet ............................................................................................ 1
• Added note 2 to Family Information table............................................................................................................................... 5
• Changed External Reference Input, Reference input current parameter typical specification from 350 to 300 .................... 8
• Added External Reference Input, Reference leakage current parameter to Electrical Characteristics.................................. 8
• Changed Power-Supply Requirements, Power-supply voltage parameter digital interface supply range as a function
of SCLK in Electrical Characteristics ...................................................................................................................................... 9
• Added Digital Inputs, Digital input leakage current parameter to Electrical Characteristics .................................................. 9
• Added true-differential input feature details to Analog Input section.................................................................................... 22
• Deleted shading from Figure 64 ........................................................................................................................................... 35
• Deleted shading from Figure 65 ........................................................................................................................................... 36
• Deleted shading from Figure 67 ........................................................................................................................................... 38
• Deleted shading from Figure 69 ........................................................................................................................................... 40
• Deleted shading from Figure 70 ........................................................................................................................................... 40
• Deleted shading from Figure 72 ........................................................................................................................................... 43
• Added power scaling with throughput feature details to Power Saving section................................................................... 45
Changes from Original (May 2013) to Revision A
Page
• Changed document status to Production Data; pre-RTM changes made throughout document .......................................... 1
Copyright © 2013–2015, Texas Instruments Incorporated
Product Folder Links: ADS8881
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