Texas Instruments | Comparing the ADS114S06 and ADS114S08 Standard and Cost-Optimized (B-Grade) ADCs | Application notes | Texas Instruments Comparing the ADS114S06 and ADS114S08 Standard and Cost-Optimized (B-Grade) ADCs Application notes

Texas Instruments Comparing the ADS114S06 and ADS114S08 Standard and Cost-Optimized (B-Grade) ADCs Application notes
Application Report
SBAA287 – May 2018
Understanding the Differences Between the ADS114S06
and ADS114S08 Standard and Cost-Optimized Versions
Bryan Lizon ................................................................................................................ Precision ADCs
ABSTRACT
This document describes the differences between the standard and cost-optimized versions of the
ADS114S06 and ADS114S08 (ADS114S0x) devices. Texas Instruments provides cost-optimized, B-grade
versions of each device for systems that may not require the performance level and feature set offered by
the standard devices. Table 1 lists the standard versus B-grade devices.
This application report also describes how the differences apply to the ADS114S08 evaluation module
(EVM) because there is no dedicated EVM for the B-grade versions.
Table 1. Standard Versus B-Grade Devices
Standard Device
B-Grade Device
ADS114S06
ADS114S06B
ADS114S08
ADS114S08B
1
2
3
4
5
6
7
Contents
Introduction ...................................................................................................................
Performance ..................................................................................................................
Features .......................................................................................................................
Specifications .................................................................................................................
EVM Differences .............................................................................................................
Alternative Device Recommendations ....................................................................................
Conclusion ....................................................................................................................
1
Functional Block Diagram
2
3
4
4
5
5
5
List of Figures
..................................................................................................
2
List of Tables
1
Standard Versus B-Grade Devices ........................................................................................ 1
2
Performance Differences Between the ADS114S0x and ADS114S0xB ............................................. 3
3
Features Available Only in Standard-Grade Devices ................................................................... 4
4
Specifications Removed From B-Grade Devices ........................................................................ 4
5
Register Settings to Mimic ADS114S0xB Behavior on the ADS114S08EVM
5
6
Pin-Compatible, 24-Bit Versions of the ADS114S06 and ADS114S08
5
......................................
..............................................
Trademarks
All trademarks are the property of their respective owners.
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Understanding the Differences Between the ADS114S06 and ADS114S08
Standard and Cost-Optimized Versions
Copyright © 2018, Texas Instruments Incorporated
1
Introduction
1
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Introduction
The 6-channel ADS114S06 and 12-channel ADS114S08 are 16-bit, 4000 sample-per-second (SPS),
delta-sigma, analog-to-digital converters (ADCs). These devices offer an integrated, analog front-end that
consists of:
• A fully-flexible input multiplexer
• Dual excitation current sources (IDACs)
• A low-noise programmable gain amplifier (PGA)
• A low-drift 2.5-V voltage reference with buffered reference output
• A temperature sensor
• A precision oscillator
• Multiple monitoring and diagnostic features
The performance and feature set make these ADCs an excellent choice for all types of precision sensor
measurements in end equipment such as:
• Pressure transmitters
• Thermal controllers
• Temperature transmitters
• PLC analog input modules
Figure 1 illustrates the functional block diagram for these two ADCs.
AVDD
AVSS-SW
REFN0
REFOUT
REFP0
Burnout
Detect
Excitation
Current
Sources
AINCOM
AIN0
Reference
MUX
2.5-V
Reference
ADS114S08
ADS114S06
VREF Detect
AIN1
AIN2
VBIAS
AIN4
Input
MUX
PGA
16-Bit
û ADC
AIN6 / REFP1
AIN7 / REFN1
START/SYNC
Reference
Buffers
AIN3
AIN5
DVDD
Configurable
Digital
Filter
RESET
Serial
Interface
And
Control
DIN
DOUT/ DRDY
PGA Rail
Detection
AIN8 / GPIO0
CS
SCLK
DRDY
AIN9 / GPIO1
AIN10 / GPIO2
Temp
Sensor
AIN11 / GPIO3
ADS114S08
Only
Supply
Monitor
System / Self
Calibration
4.096-MHz
Oscillator
CLK
Burnout
Detect
DGND
AVSS
Figure 1. Functional Block Diagram
The differences between the standard and B-grade versions are separated into three different categories:
• Performance
• Features
• Specifications
These categories are discussed in the sections that follow.
2
Understanding the Differences Between the ADS114S06 and ADS114S08
Standard and Cost-Optimized Versions
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Performance
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2
Performance
For end equipment that does not require the performance of the standard-grade ADCs, some
specifications in the ADS114S06B and ADS114S08B are relaxed. Table 2 summarizes these relaxed
specifications and compares their values to the standard-grade devices.
Table 2. Performance Differences Between the ADS114S0x and ADS114S0xB
PARAMETER
TEST CONDITIONS
ADS114S06
ADS114S08
MIN
Operating ambient temperature
Absolute input current
INL (best fit)
Gain error
VREF accuracy
VREF temperature drift
IDAC accuracy (each IDAC)
–50
PGA enabled, all gains
IDAC temperature drift matching
Oscillator accuracy
Device cost
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MIN
125
–40
TYP
UNIT
MAX
125
°C
±10
nA
0.1
±2
0.1
1
10
1
PGA enabled, gain = 1 to 8,
VCM = AVDD / 2
2
15
2
25 ppmFSR
PGA enabled, gain = 16 to
128, VCM = AVDD / 2
3
15
2
25
TA = 25°C, PGA bypassed
0.004% 0.012%
0.01%
0.1%
TA = 25°C, PGA enabled,
gain = 1 to 32
0.004% 0.012%
0.025%
0.2%
TA = 25°C, PGA enabled,
gain = 64 and 128
0.004%
0.02%
0.025%
0.2%
TA = 25°C, TQFP package
–0.05% ±0.01%
0.05%
–0.2% ±0.01%
0.2%
TA = 25°C, QFN package
–0.1% ±0.01%
0.1%
–0.2% ±0.01%
0.2%
8
40
±1%
6%
±1%
6%
TA = –40°C to +85°C
TA = –50°C to +125°C
TA = 25°C, 10 µA to 100 µA
–5%
TA = 25°C, 250 µA to 2 mA
–3%
TA = 25°C, 250 µA to 750 µA
2.5
8
3
10
±0.7%
5%
–6%
–6%
N/A
±0.5%
3%
0.15%
0.8%
0.20%
0.1%
0.6%
0.20%
0.07%
0.4%
0.20%
10 µA to 750 µA
20
120
100
1 mA to 2 mA
10
80
100
10 µA to 100 µA
3
25
10
250 µA to 2 mA
2
15
10
TA = 25°C, 1 mA to 2 mA
IDAC temperature drift
MAX
PGA bypassed,
VCM = AVDD / 2
TA = 25°C, 10 µA to 100 µA
IDAC current mismatch
TYP
ADS114S06B
ADS114S08B
–1.5%
1.5%
–2%
ADS114S06
ADS114S06B
ADS114S08
ADS114S08B
ppm/°C
ppm/°C
ppm/°C
2%
Understanding the Differences Between the ADS114S06 and ADS114S08
Standard and Cost-Optimized Versions
Copyright © 2018, Texas Instruments Incorporated
USD
($)
3
Features
3
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Features
Several features that are available in the standard-grade devices are removed from the B-grade devices.
Table 3 summarizes these features, as well as their intended purpose in the standard-grade devices.
Table 3. Features Available Only in Standard-Grade Devices
Feature
4
Purpose
SINC3 Filter
Reduces ADC noise compared to low-latency filter, while increasing settling time
Low-Side Power Switch
Power-down path for resistive bridges to reduce power consumption between conversions
Global Chop
Averages two readings to reduce offset, offset drift, and noise
PGA Rail Detection
Detects if the PGA is operating outside the linear region of operation
Reference Detection
Detects if the differential reference voltage drops below 0.3 V or [1/3 × (AVDD – AVSS)]
Cyclic Redundancy Check (CRC)
Detects single-bit or multibit data-transmission errors
Programmable Conversion Delay
User-defined programmable delay time to compensate for external analog circuitry settling time
when multiplexing through channels
Specifications
In addition to removed features, the ADS114S06B and ADS114S08B have several specifications that are
also removed. These specifications are generally unnecessary in more cost-sensitive applications that
require a balance between performance and value. Table 4 summarizes the specifications removed from
the B-grade devices.
Table 4. Specifications Removed From B-Grade Devices
Change
Specification
Differential input current
Minimum and maximum values removed
Input offset voltage
Offset drift
VREF absolute input current
Minimum values removed
CMRR
PSRR
Gain drift
Maximum values removed
Analog supply current
Digital supply current
Values not specified
4
Absolute input current drift
Differential input current drift
Understanding the Differences Between the ADS114S06 and ADS114S08
Standard and Cost-Optimized Versions
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EVM Differences
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5
EVM Differences
While there is no B-grade-specific EVM for the ADS114S06B or ADS114S08B, the behavior of these
devices can be mimicked using the standard-grade ADS114S08EVM. Table 5 identifies the bit values
within each field and register that must be fixed when using the ADS114S08EVM, so that the EVM
operates like the B-grade devices. Although this fix allows the EVM to function like the B-grade device, the
EVM performance is relaxed per Table 2 and Table 4.
Table 5. Register Settings to Mimic ADS114S0xB Behavior on the
ADS114S08EVM
Address
Register
03h
PGA
04h
REF
Bit Value
7
0
6
0
5
0
G_CHOP
7
0
FILTER
4
1
7
0
FL_REF_EN[1:0]
06h
IDACMAG
08h
VBIAS
09h
Bit No.
DELAY[2:0]
DATARATE
05h
6
Field
SYS
6
0
FL_RAIL_EN
7
0
PSW
6
0
VB_LEVEL
7
0
CRC
1
0
SENDSTAT
0
0
Alternative Device Recommendations
In addition to the 16-bit ADS114S06 and ADS114S08, Texas Instruments also offers the pin-to-pin
compatible, 24-bit devices shown in Table 6. These ADCs offer the same feature set and performance as
their 16-bit counterparts, but with 24-bit resolution.
Table 6. Pin-Compatible, 24-Bit Versions of the ADS114S06 and ADS114S08
7
Device
Description
ADS124S06
24-bit, pin-to-pin compatible with the ADS114S06
ADS124S08
24-bit, pin-to-pin compatible with the ADS114S08
Conclusion
Many types of sensor measurement end equipment often require the high-performance and extensive
feature set of the 16-bit, 6-channel ADS114S06 and 12-channel ADS114S08. However, for more costsensitive end equipment or applications, Texas Instruments offers pin-compatible, B-grade versions of
these devices (the ADS114S06B and ADS114S08B) that offer an excellent combination of performance
and cost.
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Standard and Cost-Optimized Versions
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5
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