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PDF TC7136 Data sheet ( Hoja de datos )
| Número de pieza | TC7136 | |
| Descripción | LOW POWER 3-1/2 DIGIT ANALOG-TO-DIGITAL CONVERTERS | |
| Fabricantes | TelCom | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de TC7136 (archivo pdf) en la parte inferior de esta página. Total 12 Páginas | ||
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1
TC7136
TC7136A
LOW POWER, 3-1/2 DIGIT ANALOG-TO-DIGITAL CONVERTERS
FEATURES
s Fast Overrange Recovery, Guaranteed First
Reading Accuracy
s Low Temperature Drift Internal Reference
TC7136 ....................................... 70 ppm/°C Typ
TC7136A ..................................... 35 ppm/°C Typ
s Guaranteed Zero Reading With Zero Input
s Low Noise .................................................... 15 µVP-P
s High Resolution .............................................. 0.05%
s Low Input Leakage Current ...................... 1 pA Typ
10 pA Max
s Precision Null Detectors With True Polarity at
Zero
s High-Impedance Differential Input
s Convenient 9V Battery Operation With
Low Power Dissipation ........................ 500 µW Typ
900 µW Max
TYPICAL APPLICATIONS
s Thermometry
s Bridge Readouts: Strain Gauges, Load Cells, Null
Detectors
s Digital Meters: Voltage/Current/Ohms/Power, pH
s Digital Scales, Process Monitors
s Portable Instrumentation
GENERAL DESCRIPTION
The TC7136 and TC7136A are low-power, 3-1/2 digit
with liquid crystal display (LCD) drivers with analog-to-
digital converters. These devices incorporate an "integra-
tor output zero" phase which guarantees overrange
recovery. The performance of existing TC7126, TC7126A
and ICL7126-based systems may be upgraded with minor
changes to external, passive components.
The TC7136A has an improved internal zener refer-
ence voltage circuit which maintains the analog common
temperature drift to 35 ppm/°C (typical) and 75 ppm/°C
(maximum). This represents an improvement of two to four
times over similar 3-1/2 digit converters. The costly, space-
consuming external reference source may be removed.
The TC7136/A limits linearity error to less than 1 count
on 200 mV or 2V full-scale ranges. Roll-over error — the
difference in readings for equal magnitude but opposite
polarity input signals — is below ±1 count. High-impedance
differential inputs offer 1 pA leakage currents and a 1012Ω
input impedance. The differential reference input allows
ratiometric measurements for ohms or bridge transducer
measurements. The 15 µVP-P noise performance guaran-
tees a "rock solid" reading. The auto-zero cycle guarantees
a zero display readout for a 0V input.
2
3
4
5
ORDERING INFORMATION
PART CODE
TC7136X X XXX
A or blank*
R (reversed pins) or blank (CPL pkg only)
* "A" parts have an improved reference TC
Package Code (see below):
Package
Code Package
Pin Layout
Temperature
Range
CKW
CLW
CPL
44-Pin PQFP
44-Pin PLCC
40-Pin PDIP
Formed Leads
—
Normal
0°C to +70°C
0°C to +70°C
0°C to +70°C
AVAILABLE PACKAGES
40-Pin Plastic DIP
44-Pin Plastic Quad Flat 44-Pin Plastic Chip
Package Formed Leads
Carrier PLCC
TELCOM SEMICONDUCTOR, INC.
TYPICAL OPERATING CIRCUIT
0.1 µF
+
ANALOG
INPUT
–
1 MΩ
0.01 µF
180 kΩ
0.15 µF
34
CR+EF
31 VI+N
33
CR–EF
9–19
22–25
SEGMENT
DRIVE
LCD
30 VI–N
32 ANALOG
COMMON
POL 20
BP 21 MINUS SIGN
V+ 1
BACKPLANE
28 VBUFF TC7136
240 kΩ
0.47
µF
29 CAZ
27 VINT
TC7136A
VR+EF 36
VR–EF 35
V – 26
OSC2 OSC3 OSC1
10 kΩ
+
9V
1 CONVERSION/SEC
39 38 COSC 40
ROSC 50 pF
TO ANALOG COMMON
(PIN 32)
6
7
8560 kΩ
TC7136-6 10/18/96
3-247
1 page  
LOW POWER, 3-1/2 DIGIT
ANALOG-TO-DIGITAL CONVERTERS
1
TC7136
TC7136A
TC7136/A PIN DESCRIPTION (Cont.)
Pin No.
40-Pin PDIP
Normal
33
34
(Reverse)
(8)
(7)
Name
C–REF
C+REF
35 (6) V–REF
(5) V–REF
36 (4) TEST
37 (3) OSC3
38 (2) OSC2
39 (1) OSC1
Description
See pin 34.
A 0.1 µF capacitor is used in most applications. If a large common-mode
voltage exists (for example, the VIN– pin is not at analog common), and a 200
mV scale is used, a 1 µF capacitor is recommended and will hold the roll-over
error to 0.5 count.
See pin 36.
The analog input required to generate a full-scale output (1999 counts). Place
100 mV between pins 35 and 36 for 199.9 mV full scale. Place 1V between
pins 35 and 36 for 2V full scale. See paragraph on Reference Voltage.
Lamp test. When pulled HIGH (to V+) all segments will be turned ON and the
display should read –1888. It may also be used as a negative supply for exter-
nally-generated decimal points. See paragraph under Test for additional informa-
tion.
See pin 40.
See pin 40.
Pins 40, 39 and 38 make up the oscillator section. For a 48 kHz clock (3 readings per
second) connect pin 40 to the junction of a 180 kΩ resistor and a 50 pF capacitor. The
180 kΩ resistor is tied to pin 39 and the 50 pF capacitor is tied to pin 38.
2
3
4
GENERAL THEORY OF OPERATION
(All Pin designations refer to 40-Pin Dip)
Dual-Slope Conversion Principles
The TC7136/A is a dual-slope, integrating analog-to-
digital converter. An understanding of the dual-slope con-
version technique will aid in following detailed TC7136/A
operational theory.
The conventional dual-slope converter measurement
cycle has two distinct phases:
(1) Input signal integration
(2) Reference voltage integration (deintegration)
The input signal being converted is integrated for a fixed
time period (tSI), measured by counting clock pulses. An
opposite polarity constant reference voltage is then inte-
grated until the integrator output voltage returns to zero. The
reference integration time is directly proportional to the input
signal (tRI).
In a simple dual-slope converter, a complete conversion
requires the integrator output to "ramp-up" and "ramp-
down."
A simple mathematical equation relates the input signal,
reference voltage, and integration time:
∫1
RC
tSI
0
VIN(t) dt =
VR tRI
RC
,
TELCOM SEMICONDUCTOR, INC.
ANALOG
INPUT
SIGNAL
CINT
INTEGRATOR
–
+
COMPARATOR
–
+
5
REF
VOLTAGE
SWITCH
DRIVER
PHASE
CONTROL
CONTROL
LOGIC
POLARITY CONTROL
CLOCK
6
DISPLAY
COUNTER
VIN Ϸ VFULL SCALE
VIN Ϸ 1.2 VFULL SCALE
FIXED
SIGNAL
INTEGRATE
TIME
VARIABLE
REFERENCE
INTEGRATE
TIME
Figure 1. Basic Dual-Slope Converter
where:
VR = Reference voltage
tSI = Signal integration time (fixed)
tRI = Reference voltage integration time (variable).
For a constant VIN:
[ ]VIN = VR
tRI
tSI .
3-251
7
8
5 Page 
LOW POWER, 3-1/2 DIGIT
ANALOG-TO-DIGITAL CONVERTERS
1
TC7136
TC7136A
analog common is a very stable potential with excellent
temperature stability (typically 35 ppm/°c). for TC7136A
This potential can be used to generate the TC7136A's
reference voltage. An external voltage reference will be
unnecessary in most cases because of the 35 ppm/°C
temperature coefficient. See TC7136A Internal Voltage
Reference discussion.
TEST (Pin 37)
The TEST pin potential is 5V less than V+. TEST may be
used as the negative power supply connection for external
CMOS logic. The TEST pin is tied to the internally-generated
negative logic supply through a 500Ω resistor. The TEST pin
load should not be more than 1 mA. See the Applications
Section for additional information on using TEST as a
negative digital logic supply.
If TEST is pulled high (to V+), all segments plus the
minus sign will be activated. DO NOT OPERATE IN THIS
MODE FOR MORE THAN SEVERAL MINUTES. With TEST
= V+, the LCD segments are impressed with a DC voltage
which will destroy the LCD.
TC7136A Internal Voltage Reference
The TC7136 analog common voltage temperature sta-
bility has been significantly improved (Figure 9). The "A"
version of the industry-standard TC7136 device allows
users to upgrade old systems and design new systems
without external voltage references. External R and C val-
ues do not need to be changed; however, noise perfor-
mance will be improved by increasing CAZ. (See Auto-Zero
Capacitor section.) Figure 10 shows analog common sup-
plying the necessary voltage reference for the TC7136/A.
200
180
GUARANTEED
160 MAXIMUM NO MAXIMUM
SPECIFIED
140 TYPICAL
120
100
GUARANTEED
80 MAXIMUM TYPICAL
60
40 TYPICAL
20
TC7136A
TC7136
ICL7136
0
Figure 9. Analog Common Temperature Coefficient
TELCOM SEMICONDUCTOR, INC.
9V
2+
26
V–
1
V+
240 kΩ
TC7136
TC7136A
VR+EF 36
VR– EF
ANALOG
COMMON
VREF
35
32
10 kΩ
3
SET VREF = 1/2 VFULL SCALE
Figure 10. TC7136A Internal Voltage Reference Connection
APPLICATIONS INFORMATION
Liquid Crystal Display Sources
4
Several manufacturers supply standard LCDs to inter-
face with the TC7136A 3-1/2 digit analog-to-digital con-
verter.
Manufacturer Address/Phone
Representative
Part Numbers*
Crystaloid
Electronics
5282 Hudson Dr.
Hudson, OH 44236
216-655-2429
C5335, H5535,
T5135, SX440
AND
720 Palomar Ave.
Sunnyvale, CA 94086
408-523-8200
FE 0201, 0501
FE 0203, 0701
FE 2201
VGI, Inc.
1800 Vernon St. Ste. 2 I1048, I1126
Roseville, CA 95678
916-783-7878
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.
Decimal Point and Annunciator Drive
5
6
7
The TEST pin is connected to the internally-generated
digital logic supply ground through a 500Ω resistor. The
TEST pin may be used as the negative supply for external
CMOS gate segment drivers. LCD annunciators for decimal
points, low battery indication, or function indication may be
added without adding an additional supply. No more than 1
mA should be supplied by the TEST pin: its potential is
approximately 5V below V+.
8
3-257
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet TC7136.PDF ] | |
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