SAR ADC. ADS8678 Datasheet

ADS8678 ADC. Datasheet pdf. Equivalent

ADS8678 Datasheet
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Part ADS8678
Description SAR ADC
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Texas Instruments ADS8678
Product
Folder
Sample &
Buy
Technical
Documents
Tools &
Software
Support &
Community
Reference
Design
ADS8674, ADS8678
SBAS627 – JULY 2015
ADS867x 14-Bit, 500-kSPS, 4- and 8-Channel, Single-Supply, SAR ADCs with
Bipolar Input Ranges
1 Features
1 14-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: ±0.2 LSB; INL: ±0.25 LSB
– Low Drift for Gain Error and Offset
– SNR: 85 dB; THD: –100 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
ADS8678
ADS8674
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
14-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 ADS8674 and ADS8678 are 4- and 8-channel,
integrated data acquisition systems based on a 14-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 ADS8674 and ADS8678 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)
ADS867x
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
-0.01
-0.03
-0.05
±40
---- ± 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
±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.



Texas Instruments ADS8678
ADS8674, ADS8678
SBAS627 – 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.................... 10
7.7 Typical Characteristics ............................................ 11
8 Detailed Description ............................................ 22
8.1 Overview ................................................................. 22
8.2 Functional Block Diagram ....................................... 22
8.3 Feature Description................................................. 23
8.4 Device Functional Modes........................................ 36
8.5 Register Maps ......................................................... 49
9 Application and Implementation ........................ 65
9.1 Application Information............................................ 65
9.2 Typical Applications ................................................ 65
10 Power-Supply Recommendations ..................... 68
11 Layout................................................................... 69
11.1 Layout Guidelines ................................................. 69
11.2 Layout Example .................................................... 70
12 Device and Documentation Support ................. 71
12.1 Documentation Support ........................................ 71
12.2 Related Links ........................................................ 71
12.3 Community Resources.......................................... 71
12.4 Trademarks ........................................................... 71
12.5 Electrostatic Discharge Caution ............................ 71
12.6 Glossary ................................................................ 71
13 Mechanical, Packaging, and Orderable
Information ........................................................... 72
4 Revision History
DATE
July 2014
REVISION
*
NOTES
Initial release.
2 Submit Documentation Feedback
Product Folder Links: ADS8674 ADS8678
Copyright © 2015, Texas Instruments Incorporated



Texas Instruments ADS8678
www.ti.com
5 Device Comparison Table
PRODUCT
ADS8674
ADS8678
RESOLUTION (Bits)
14
14
CHANNELS
4, single-ended
8, single-ended
ADS8674, ADS8678
SBAS627 – JULY 2015
SAMPLE RATE (kSPS)
500
500
6 Pin Configuration and Functions
SDI 1
RST/PD 2
DAISY 3
REFSEL 4
REFIO 5
REFGND 6
REFCAP 7
AGND 8
AVDD 9
AUX_IN 10
AUX_GND 11
NC 12
NC 13
NC 14
NC 15
AIN_0P 16
AIN_0GND 17
AIN_1P 18
AIN_1GND 19
ADS8674
DBT Package
38-Pin TSSOP
Top View (Not to Scale)
38 CS
37 SCLK
36 SDO
35 ALARM
34 DVDD
33 DGND
32 AGND
31 AGND
30 AVDD
29 AGND
28 AGND
27 NC
26 NC
25 NC
24 NC
23 AIN_3P
22 AIN_3GND
21 AIN_2P
20 AIN2_GND
SDI 1
RST/PD 2
DAISY 3
REFSEL 4
REFIO 5
REFGND 6
REFCAP 7
AGND 8
AVDD 9
AUX_IN 10
AUX_GND 11
AIN_6P 12
AIN_6GND 13
AIN_7P 14
AIN_7GND 15
AIN_0P 16
AIN_0GND 17
AIN_1P 18
AIN_1GND 19
ADS8678
38 CS
37 SCLK
36 SDO
35 ALARM
34 DVDD
33 DGND
32 AGND
31 AGND
30 AVDD
29 AGND
28 AGND
27 AIN_5P
26 AIN_5GND
25 AIN_4P
24 AIN_4GND
23 AIN_3P
22 AIN_3GND
21 AIN_2P
20 AIN2_GND
NO.
1
2
3
4
5
6
7
8
9
10
11
PIN
NAME
ADS8674
ADS8678
SDI
RST/PD
DAISY
REFSEL
REFIO
REFGND
REFCAP
AGND
AVDD
AUX_IN
AUX_GND
Pin Functions
I/O DESCRIPTION
Digital input
Data input for serial communication.
Digital input
Active low logic input.
Dual functionality to reset or power-down the device.
Digital input
Chain the data input during serial communication in daisy-chain mode.
Digital input
Analog input, output
Active low logic input to enable the internal reference.
When low, the internal reference is enabled;
REFIO becomes an output that includes the VREF voltage.
When high, the internal reference is disabled;
REFIO becomes an input to apply the external VREF voltage.
Internal reference output and external reference input pin. Decouple with REFGND on pin 6.
Power supply
Reference GND pin; short to the analog GND plane.
Decouple with REFIO on pin 5 and REFCAP on pin 7.
Analog output ADC reference decoupling capacitor pin. Decouple with REFGND on pin 6.
Power supply Analog ground pin. Decouple with AVDD on pin 9.
Power supply Analog supply pin. Decouple with AGND on pin 8.
Analog input
Auxiliary input channel: positive input. Decouple with AUX_GND on pin 11.
Analog input
Auxiliary input channel: negative input. Decouple with AUX_IN on pin 10.
Copyright © 2015, Texas Instruments Incorporated
Product Folder Links: ADS8674 ADS8678
Submit Documentation Feedback
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