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PDF TC811 Data sheet ( Hoja de datos )
| Número de pieza | TC811 | |
| Descripción | 3-1/2 Digit Analog-To-Digital Converter with Hold and Differential Reference Inputs | |
| Fabricantes | Microchip Technology | |
| Logotipo |  |
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TC811
3-1/2 Digit Analog-To-Digital Converter with Hold and
Differential Reference Inputs
FEATURES
s Differential Reference Input
s Display Hold Function
s Fast Over-Range Recovery, Guaranteed Next
Reading Accuracy
s Low Temperature Drift Internal
Reference ....................................... 35ppm/°C (Typ)
s Guaranteed Zero Reading With Zero Input
s Low Noise ..................................................... 15µVp-p
s High Resolution (0.05%) and Wide Dynamic
Range (72 dB)
s High Impedance Differential Input
s Low Input Leakage Current .................... 1pA (Typ)
10pA Max
s Direct LCD Drive -No External Components
s Precision Null Detection with True Polarity at Zero
s Crystal Clock Oscillator
s Available in DIP, Compact Flat Package or PLCC
s Convenient 9V Battery Operation with
Low Power Dissipation (600µA Typical, 1mW
Maximum)
FUNCTIONAL BLOCK DIAGRAM
TYPICAL APPLICATIONS
s Thermometry
s Digital Meters
— Voltage/Current/Power
— pH Measurement
— Capacitance/Inductance
— Fluid Flow Rate/Viscosity
— Humidity
— Position
s Panel Meters
s LVDT Indicators
s Portable Instrumentation
s Digital Scales
s Process Monitors
s Gaussometers
s Photometers
ORDERING INFORMATION
Part No.
TC811CKW
TC811CPL
Package
Temp.
Range
Max VREF
Temp. Co.
44-Pin PQFP 0°C to +70°C 75 ppm/°C
40-Pin Plastic DIP 0°C to +70°C 75 ppm/°C
TYPICAL SEGMENT OUTPUT
V+
0.5mA
2mA
SEGMENT
OUTPUT
LCD DISPLAY
TC811CPL
C
+
REF
CREF
VR+EF
VR–EF
35 36
33
RINT
C
–
REF
VBUFF
V+
34 28 38
10
µA
V
+
IN
31
INT
A/Z
ANALOG 32
COMMON
V
–
IN
30
INT
ZI & A/Z
ZI &
A/Z
–
+
ZI
DE DE
(–) (+)
DE (+) DE (–)
AZ & DE (±)
–
+
V+– 3.0V
26
V–
LOW
TEMPCO
VREF
INTERNAL DIGITAL GROUND
CAZ
CINT
VINT
29 27
INTEGRATOR
–
+
+
–
A/Z
TO
DIGITAL
SECTION
COMPARATOR
THOUSANDS
BACKPLANE
21
LCD SEGMENT DRIVERS
7 SEGMENT 7 SEGMENT 7 SEGMENT
DECODE
DECODE
DECODE
200
DATA LATCH
HUNDREDS
TENS
UNITS
TO SWITCH DRIVERS
FROM COMPARATOR OUTPUT
CLOCK
fOSC
4
≈70kΩ
CONTROL LOGIC
40
OSC 1
39
22MΩ
OSC2
INTERNAL DIGITAL GOUND
VTH
= 1V
1
HLDR
38 V+
6.2V
500Ω
TEST
26 V–
10pF
V+
470k
20pF
V+
© 2001 Microchip Technology Inc. DS21472A
TC811-7 11/5/96
1 page  
3-1/2 Digit Analog-To-Digital Converter with
Hold and Differential Reference Inputs
TC811
0.1µF
+
ANALOG
INPUT
–
1MΩ
0.01µF
180kΩ
0.068µF
35
CR+ EF
31 VI+N
33
C
34
REF
9–19
22–25
SEGMENT
DRIVE
30 VI–N TC811
32
ANALOG
COMMON
POL 20
BP 21 MINUS SIGN
V+ 38
LCD
BACKPLANE
28 VBUFF
0.47
µF
29 CAZ
27 VINT
OSC2
39
HLDR 1
VR+EF 36
VR–EF 33
V – 26
OSC1
40
240kΩ
10k Ω
+
9V
2 CONVERSION/SEC
22MΩ
TO ANALOG COMMON
(PIN 32)
20pF 470k
V+
10pF
V+
Figure 1. Typical Operating Circuit
GENERAL THEORY OF OPERATION
Dual-Slope Conversion Principles
(All Pin Designations Refer to 40-Pin DIP Package)
The TC811 is a dual slope, integrating analog-to-digital
converter. An understanding of the dual slope conversion
technique will aid the user in following the detailed TC811
theory of operation following this section. A conventional
dual slope converter measurement cycle has two distinct
phases:
1) Input Signal Integration
2) Reference Voltage Integration (Deintegration)
Referring to Figure 2, the unknown input signal to be
converted is integrated from zero for a fixed time period
(TINT), measured by counting clock pulses. A constant
reference voltage of the opposite polarity is then integrated
until the integrator output voltage returns to zero. The
reference integration (deintegration) time (TDEINT) is then
directly proportional to the unknown input voltage (VIN).
In a simple dual slope converter, a complete conversion
requires the integrator output to “ramp-up” from zero and
“ramp-down” back to zero. A simple mathematical equation
relates the input signal, reference voltage and integration
time:
∫1
RINT CINT
tINT
VIN(t) dt =
0
VREF tDEINT
RINT CINT
where:
VREF = Reference voltage
tINT = Integration Time
tDEINT = Deintegration Time
ANALOG
INPUT
SIGNAL
C
INTEGRATOR
–
+
COMPARATOR
–
+
+/–
REF
VOLTAGE
SWITCH
DRIVER
PHASE
CONTROL
CONTROL
LOGIC
POLARITY CONTROL
CLOCK
DISPLAY
COUNTER
VIN ≈ VFULL SCALE
VIN ≈ 1.2 VFULL SCALE
FIXED
SIGNAL
INTEGRATE
TIME
VARIABLE
REFERENCE
INTEGRATE
TIME
Figure 2. Basic Dual Slope Converter
30
20
10
0
0.1/T
T = MEASUREMENT PERIOD
1/T
INPUT FREQUENCY
10/T
Figure 3. Normal-Mode Rejection of
Dual Slope Converter
For a constant VINT:
[ ]tDEINT
VIN = VREF tINT
© 2001 Microchip Technology Inc. DS21472A
5
TC811-7 11/5/96
5 Page 
3-1/2 Digit Analog-To-Digital Converter with
Hold and Differential Reference Inputs
TC811
Liquid Crystal Display Sources
Several LCD manufactures supply standard LCD dis-
plays to interface with the TC811 3-1/2 digit analog-to-digital
converter.
Manufacturer Address/Phone
Representative
Part Numbers*
Crystaloid
Electronics
5282 Hudson Dr.,
Hudson, OH 44236
216-655-2429
C5335, H5535,
T5135, SX440
AND
770 Airport Blvd.,
Burlingame, CA 94010
415-347-9916
FE 0801,
FE 0203
EPSON
3415 Kashikawa St.,
Torrence, CA 90505
212-534-0360
LD-B709BZ
LD-H7992AZ
Hamlin, Inc.
612 E. Lake St.,
Lake Mills, WI 53551
414-648-2361
3902, 3933, 3903
*NOTE: Contact LCD manufacturer for full product listing/specifications.
Oscillator Crystal Source
Manufacturer
STATEK
Address/Phone
512 N-Main
Orange, CA 92668
714-639-7810
Representative
Part Numbers
CX-1V 40.0
Ratiometric Resistance Measurements
The TC811 true differential input and differential refer-
ence make ratiometric readings possible. In ratiometric
operation, an unknown resistance is measured with respect
to a known standard resistance. No accurately defined
reference voltage is needed.
The unknown resistance is put in series with a known
standard and a current is passed through the pair (Figure
11). The voltage developed across the unknown is applied
to the input and the voltage across the known resistor
applied to the reference input. If the unknown equals the
standard, the input voltage will equal the reference voltage
and the display will read 1000. The displayed reading can be
determined from the following expression:
Displayed reading = RUNKNOWN x 1000
RSTANDARD
The display will overrange for RUNKNOWN ≥ 2 X
RSTANDARD.
9V
+
26
V–
38
V+
TC811
240kΩ
VR+EF 36
VREF
VR– EF 33
ANALOG 32
COMMON
10kΩ
SET VREF = 1/2 VFULL SCALE
Figure 10. TC811 Internal Voltage Reference Connection
RSTANDARD
RUNKNOWN
VR+EF V+ HLDR
VR–EF
VI+N TC811
VI–N
ANALOG
COMMON
LCD
Figure 11. Low Parts Count Ratio Metric Resistance Measurement
© 2001 Microchip Technology Inc. DS21472A
11
TC811-7 11/5/96
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet TC811.PDF ] | |
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