廬
APPLICATION BULLETIN
Mailing Address: PO Box 11400, Tucson, AZ 85734 鈥?Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 鈥?Tel: (520) 746-1111
Telex: 066-6491 鈥?FAX (520) 889-1510 鈥?Product Info: (800) 548-6132 鈥?Internet: www.burr-brown.com/ 鈥?FAXLine: (800) 548-6133
VOLTAGE REFERENCE SCALING TECHNIQUES
Increase the Accuracy of the Converter as well as Resolution
By Bonnie Baker
Temperature sensing can be one of the more challenging
physical entities to measure if a variety of ranges and levels
of accuracy are required by one electrical system. The circuit
in Figure 1 uses a low power, single-supply analog-to-digital
converter, ADS7816, configured with a thermocouple and
CJC sub-circuit to achieve the desired range of responsive-
ness as well as high accuracy. The thermocouple is inter-
faced with a 12-bit A/D converter that allows for an adjust-
able input range. This range is adjusted with the voltage
reference input. The range of the voltage reference input of
the ADS7816 A/D converter is from the supply voltage
(+5V typically) all the way down to 0.1V. The voltage
reference range mimics a gain stage for the 12-bit converter.
With this converter a suto-gain stage provides 17.6-bit
virtual resolution against a 5V scale. When this circuit is
properly calibrated for the desired temperature range, the
effective resolution can be increased by 50x over a system
with a standard 5V full-scale range.
Other converters in the same family include the ADS1286
and ADS7817 (see Table I). All three of these products have
the unique characteristics of having a variable input range,
while also being low power, low cost and available in 8-pin
packages (such as PDIP, SOIC and MSOP). This product
line, also known as the fly-spec converters, is only the
beginning of a new family of converters that take advantage
of the versatile reference function and compact architecture.
This application bulletin addresses the uniqueness of the
voltage reference function to the A/D conversion process.
1
3
4
ADS1286
Input
Configuration
Maximum
Sampling Rate
Voltage
Reference
Range
Analog Input
Voltage Range
Supply Voltage
Range
Minimum LSB
Size to 12 Bits
Minimum
Achievable LSB
Single-Ended
w/Sense Pin
20kHz
100mV to
Supply
V
REF
ADS7816
Single-Ended
w/Sense Pin
200kHz
100mV to
Supply
V
REF
ADS7817
Full
Differential
200kHz
50mV to
Supply
2V
REF
4.5V - 5.25V
24.4碌V
51.79碌V
4.5V - 5.25V
24.4碌V
51.79碌V
4.75V - 5.25V
24.4碌V
51.79碌V
TABLE I. Flyspec 12-Bit, Single Supply Converter Product
Line Capable of Achieving Very Small Actual
LSB Values.
+5V
+5V
+5V
R
8
460k鈩?/div>
ISO
Thermal
Block
D
1
Chromel
0.4V
R
1
150k鈩?/div>
R
3
1M鈩?/div>
R
2
59k鈩?/div>
R
6
1M鈩?/div>
C
3
0.1碌F
V
REF
DCLOCK
ADS7816
D
OUT
CS/SHDN
U
1
R
5
1k鈩?/div>
C
5
0.1碌F
碌P
3-Wire
Interface
U
4
A
0
A
1
TC
3
R
4
1k鈩?/div>
Copper
C
4
0.1碌F
U
3
R
11
1k鈩?/div>
0.1V
R
12
1k鈩?/div>
100鈩?/div>
OPA237
C
2
0.1碌F
U
2
C
1
10碌F
MUX
R
10
1k鈩?/div>
0.2V
R
9
1k鈩?/div>
0.3V
TC
1
E-Type Thermocouple
TC
2
Constantan
FIGURE 1. Thermocouple Application Using a MUX to Scale the Input Range of an Analog-to-Digital Converter in Order
to Increase Accuracy as well as Resolution.
漏
1997 Burr-Brown Corporation
AB-110
Printed in U.S.A. February, 1997
AB-110相關型號PDF文件下載
-
型號
版本
描述
廠商
下載
-
英文版
Application Bulletin AB-12
FAIRCHILD
-
英文版
Application Bulletin AB-12
FAIRCHILD ...
-
英文版
AB-100 - MULTIPLEXER DATA ACQUISTION SYSTEM
ETC
-
英文版
AB-101 - COMBINING AN AMPLIFIER WITH THE BUF634
ETC
-
英文版
AB-102 - OUTPUT SPECTRUM AND POST-LPF DESIGN OF THE PCM1710
ETC
-
英文版
AB-103 - NOISE ANALYSIS FOR HIGH SPEED OP AMPS
ETC
-
英文版
ETC
-
英文版
AB-105 - TUNING IN AMPLIFIERS
ETC
-
英文版
AB-106 - PROGRAMMING TRICKS FOR HIGHER CONVERSION SPEEDS UTI...
ETC
-
英文版
AB-107 - GIVING CONVERTERS A LITTLE GAIN BOOST WITH A FRONT ...
ETC
-
英文版
AB-109 - ADS7809 TAG FEATURE
ETC
-
英文版
AB-110 - VOLTAGE REFERENCE SCALING TECHNIQUES Increase the A...
ETC
-
英文版
AB-111 - DEM-ADS1210
ETC
-
英文版
ETC
-
英文版
AB-113 - ACCESSING THE ADS1210 DEMO BOARD WITH YOUR PC
ETC
-
英文版
AB-115 - OVERDRIVING THE INPUTS TO THE ADS1210. ADS1211. ADS...
ETC
-
英文版
ETC
-
英文版
ETC
-
英文版
AB-118 - EXTRACT AND DIGITIZE AC SIGNALS WITH A SINGLE A
ETC
-
英文版
＂AB-119 - A ＂＂GETTING STARTED＂＂ GUIDE FOR THE CONVERTER...
ETC
1
2
3
