SAR ADC. ADS8688A Datasheet

ADS8688A Datasheet PDF


Part Number

ADS8688A

Description

SAR ADC

Manufacture

etcTI

Total Page 30 Pages
Datasheet
Download ADS8688A Datasheet


ADS8688A
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ADS8684A, ADS8688A
SBAS680 – JULY 2015
ADS868xA 16-Bit, 500-kSPS, 4- and 8-Channel, Single-Supply, SAR ADCs with
Bipolar Input Ranges
1 Features
1 16-Bit ADCs with Integrated Analog Front-End
• 4-, 8-Channel MUX with Auto and Manual Scan
• Channel-Independent Programmable Inputs:
– ±10.24 V, ±5.12 V, ±2.56 V, ±1.28 V, ±0.64 V
– 10.24 V, 5.12 V, 2.56 V, 1.28 V
• 5-V Analog Supply: 1.65-V to 5-V I/O Supply
• Constant Resistive Input Impedance: 1 MΩ
• Input Overvoltage Protection: Up to ±20 V
• On-Chip, 4.096-V Reference with Low Drift
• Excellent Performance:
– 500-kSPS Aggregate Throughput
– DNL: ±0.5 LSB; INL: ±0.75 LSB
– Low Drift for Gain Error and Offset
– SNR: 92 dB; THD: –102 dB
– Low Power: 65 mW
• AUX Input Direct Connection to ADC Inputs
• ALARM High and Low Thresholds per Channel
• SPI™-Compatible Interface with Daisy-Chain
• Industrial Temperature Range: –40°C to 125°C
• TSSOP-38 Package (9.7 mm × 4.4 mm)
1 M:
AIN_0P
OVP
AIN_0GND
OVP
1 M:
1 M:
AIN_1P
OVP
AIN_1GND
OVP
1 M:
1 M:
AIN_2P
OVP
AIN_2GND
OVP
1 M:
1 M:
AIN_3P
OVP
AIN_3GND
OVP
1 M:
1 M:
AIN_4P
OVP
AIN_4GND
OVP
1 M:
1 M:
AIN_5P
OVP
AIN_5GND
OVP
1 M:
1 M:
AIN_6P
OVP
AIN_6GND
OVP
1 M:
1 M:
AIN_7P
OVP
AIN_7GND
OVP
1 M:
AUX_IN
AUX_GND
Block Diagram
AVDD
DVDD
PGA
2nd-Order
LPF
ADC
Driver
VB0
ADS8688A
ADS8684A
PGA
2nd-Order
LPF
ADC
Driver
VB1
PGA
2nd-Order
LPF
ADC
Driver
VB2
PGA
2nd-Order
LPF
ADC
Driver
VB3
PGA
2nd-Order
LPF
ADC
Driver
VB4
PGA
2nd-Order
LPF
ADC
Driver
VB5
PGA
2nd-Order
LPF
ADC
Driver
VB6
PGA
2nd-Order
LPF
ADC
Driver
VB7
Digital
Logic
and
Interface
CS
SCLK
SDI
16-Bit
SAR ADC
SDO
DAISY
Oscillator
REFSEL
RST / PD
ALARM
REFCAP
REFIO
4.096-V
Reference
AGND
DGND
REFGND
1
2 Applications
• Power Automation
• Protection Relays
• PLC Analog Input Modules
3 Description
The ADS8684A and ADS8688A are 4- and 8-
channel, integrated data acquisition systems based
on a 16-bit successive approximation (SAR) analog-
to-digital converter (ADC), operating at a throughput
of 500 kSPS. The devices feature integrated analog
front-end circuitry for each input channel with
overvoltage protection up to ±20 V, a 4- or 8-channel
multiplexer with automatic and manual scanning
modes, and an on-chip, 4.096-V reference with low
temperature drift. Operating on a single 5-V analog
supply, each input channel on the devices can
support true bipolar input ranges of ±10.24 V,
±5.12 V, ±2.56 V, ±1.28V and ±0.64V, as well as
unipolar input ranges of 0 V to 10.24 V, 0 V to 5.12 V,
0 V to 2.56 V and 0 V to 1.28 V. The gain of the
analog front-end for all input ranges is accurately
trimmed to ensure a high dc precision. The input
range selection is software-programmable and
independent for each channel. The devices offer a
1-MΩ constant resistive input impedance irrespective
of the selected input range.
The ADS8684A and ADS8688A offer a simple SPI-
compatible serial interface to the digital host and also
support daisy-chaining of multiple devices. The digital
supply operates from 1.65 V to 5.25 V, enabling
direct interface to a wide range of host controllers.
Device Information(1)
PART NUMBER
PACKAGE
BODY SIZE (NOM)
ADS868xA
TSSOP (38)
9.70 mm × 4.40 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Gain Error versus Temperature
0.05
0.03
0.01
---- ± 2.5*VREF, ---- “ 1.25*VREF
---- “ 0.625*VREF, ------“0.3125*VREF
-------“0.156 VREF, ---- + 2.5*VREF
---- + 1.25*VREF, ---- + 0.625*VREF
---- + 0.3125*VREF
-0.01
-0.03
-0.05
±40
±7 26 59 92
Free-Air Temperature (oC)
125
C039
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.

ADS8688A
ADS8684A, ADS8688A
SBAS680 – JULY 2015
www.ti.com
Table of Contents
1 Features .................................................................. 1
2 Applications ........................................................... 1
3 Description ............................................................. 1
4 Revision History..................................................... 2
5 Device Comparison Table..................................... 3
6 Pin Configuration and Functions ......................... 3
7 Specifications......................................................... 5
7.1 Absolute Maximum Ratings ...................................... 5
7.2 ESD Ratings.............................................................. 5
7.3 Recommended Operating Conditions....................... 5
7.4 Thermal Information .................................................. 5
7.5 Electrical Characteristics........................................... 6
7.6 Timing Requirements: Serial Interface.................... 11
7.7 Typical Characteristics ............................................ 12
8 Detailed Description ............................................ 23
8.1 Overview ................................................................. 23
8.2 Functional Block Diagram ....................................... 23
8.3 Feature Description................................................. 24
8.4 Device Functional Modes........................................ 37
8.5 Register Maps ......................................................... 50
9 Application and Implementation ........................ 66
9.1 Application Information............................................ 66
9.2 Typical Applications ................................................ 66
10 Power-Supply Recommendations ..................... 69
11 Layout................................................................... 70
11.1 Layout Guidelines ................................................. 70
11.2 Layout Example .................................................... 71
12 Device and Documentation Support ................. 72
12.1 Documentation Support ........................................ 72
12.2 Related Links ........................................................ 72
12.3 Community Resources.......................................... 72
12.4 Trademarks ........................................................... 72
12.5 Electrostatic Discharge Caution ............................ 72
12.6 Glossary ................................................................ 72
13 Mechanical, Packaging, and Orderable
Information ........................................................... 73
4 Revision History
DATE
July 2014
REVISION
*
NOTES
Initial release.
2 Submit Documentation Feedback
Copyright © 2015, Texas Instruments Incorporated
Product Folder Links: ADS8684A ADS8688A





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