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PDF TC7135 Data sheet ( Hoja de datos )
| Número de pieza | TC7135 | |
| Descripción | 4-1/2 DIGIT ANALOG-TO-DIGITAL CONVERTER | |
| Fabricantes | TelCom | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de TC7135 (archivo pdf) en la parte inferior de esta página. Total 13 Páginas | ||
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1
TC7135
4-1/2 DIGIT ANALOG-TO-DIGITAL CONVERTER
FEATURES
s Low Roll-Over Error ......................... ±1 Count Max
s Guaranteed Nonlinearity Error ........ ±1 Count Max
s Guaranteed Zero Reading for 0V Input
s True Polarity Indication at Zero for Null Detection
s Multiplexed BCD Data Output
s TTL-Compatible Outputs
s Differential Input
s Control Signals Permit Interface to UARTs and
µProcessors
s Auto-Ranging Supported With Overrange and
Underrange Signals
s Blinking Display Visually Indicates Overrange
Condition
s Low Input Current ............................................. 1 pA
s Low Zero Reading Drift ............................... 2 µV/°C
s Interfaces to TC7211A (LCD) and TC7212A (LED)
Display Drivers
s Available in DIP and Surface-Mount Packages
GENERAL DESCRIPTION
The TC7135 4-1/2 digit analog-to-digital converter (ADC)
offers 50 ppm (1 part in 20,000) resolution with a maximum
nonlinearity error of 1 count. An auto-zero cycle reduces zero
error to below 10 µV and zero drift to 0.5 µV/°C. Source
impedance errors are minimized by a 10 pA maximum input
current. Roll-over error is limited to ±1 count.
By combining the TC7135 with a TC7211A (LCD) or
TC7212A (LED) driver, a 4-1/2 digit display DVM or DPM can
be constructed. Overrange and underrange signals support
automatic range switching and special display blanking/flash-
ing applications.
Microprocessor-based measurement systems are sup-
ported by BUSY, STROBE, and RUN/HOLD control signals.
Remote data acquisition systems with data transfer via UARTs
are also possible. The additional control pins and multiplexed
BCD outputs make the TC7135 the ideal converter for dis-
play or microprocessor-based measurement systems.
ORDERING INFORMATION
2
3
4
Part No.
TC7135CBU
TC7135CLI
TC7135CPI
Package
64-Pin Plastic
Flat Package
28-Pin PLCC
28-Pin Plastic DIP
Temperature
Range
0°C to +70°C
5
0°C to +70°C
0°C to +70°C
TYPICAL 4-1/2 DIGIT DVM WITH LCD
4-1/2 DIGIT LCD
6.8 k Ω
+5V
+5V
TC04
0.1 µF
ANALOG
GROUND
1 µF
INPUT
0.1
µF
100 k Ω
–5V
1
V
28
UR
2
REF IN
27
OR
100 k Ω 3 ANALOG
0.47 µF
4
COMMON
INT OUT
26
STROBE
25
RUN/HOLD
1 µF 5
AZ IN
24
DGND
6
BUFF OUT
23
POL
100 k Ω
7
8
9
CC+RR– EEFF
–INPUT
22
CLOCK
21
BUSY
20
D1
10
+INPUT
19
D2
+5V 11 V +
18
D3
12
D5
17
D4
13
B1
TC7135
16
B8
14
B2
B4 15
1 16 15 14 12 5 3 4
CD4054A
7 8 13 11 10 9 2 6
120 Hz = 3 READING/SEC
CLOCK IN
1/4 CD4030
CD4081
+5V
SEGMENT
D
R
I
V
BACKPLANE
E
+5V
5 BP
1
V+
31 D1
32 D2
SEG
33 D3
OUT
34 D4
2,3,4
6–26
37–40
30 B3 TC7211A
29
B2
OSC 36
+5V
28
B1
OPTIONAL
CAP
27 B0
GND 35
6
7
8
TELCOM SEMICONDUCTOR, INC.
TC7135-10 11/6/96
3-113
1 page  
4-1/2 DIGIT
ANALOG-TO-DIGITAL CONVERTER
1
TC7135
SW I
+ IN
SW
–
RI
SW
+
RI
REF
IN
SWR
CREF
SWZ
ANALOG
COM
SW
+
RI
SW
–
RI
ANALOG
INPUT BUFFER
+
RINT
–
SWIZ SWZ
SWZ
CINT
CSZ
–
+
INTEGRATOR
COMPARATOR
+
– TO
DIGITAL
SECTION
SW I
– IN
SW1
SWITCH OPEN
SWITCH CLOSED
Figure 3E. Integrator Output Zero Phase
GENERAL THEORY OF OPERATION
(All Pin Designations Refer to 28-Pin DIP)
Dual-Slope Conversion Principles
The TC7135 is a dual-slope, integrating analog-to-
digital converter. An understanding of the dual-slope con-
version technique will aid in following detailed TC7135
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, measured by counting clock pulses. An oppo-
site polarity constant reference voltage is then integrated
until the integrator output voltage returns to zero. The
reference integration time is directly proportional to the input
signal.
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 tSI VIN(t) dt = VR tRI ,
RC 0
RC
where:
VR = Reference voltage
tSI = Signal integration time (fixed)
tRI = Reference voltage integration time (variable).
TELCOM SEMICONDUCTOR, INC.
For a constant VIN:
[ ]VIN = VR
tRI .
tSI
The dual-slope converter accuracy is unrelated to the
integrating resistor and capacitor values, as long as they are
stable during a measurement cycle. Noise immunity is an
inherent benefit. Noise spikes are integrated, or averaged,
to zero during integration periods. Integrating ADCs are
immune to the large conversion errors that plague succes-
sive approximation converters in high-noise environments.
(See Figure 4.)
2
3
TC7135 Operational Theory
The TC7135 incorporates a system zero phase and
integrator output voltage zero phase to the normal two-
phase dual-slope measurement cycle. Reduced system
errors, fewer calibration steps, and a shorter overrange
recovery time result.
The TC7135 measurement cycle contains four phases:
(1) System zero
(2) Analog input signal integration
(3) Reference voltage integration
(4) Integrator output zero
Internal analog gate status for each phase is shown in
Table 1.
4
5
ANALOG
INPUT
SIGNAL
INTEGRATOR
–
+
–COMPARATOR
+
6
REF
VOLTAGE
SWITCH
DRIVER
PHASE
CONTROL
CONTROL
LOGIC
POLARITY CONTROL
CLOCK
DISPLAY
COUNTER
VIN Ϸ VFULL SCALE
VIN Ϸ 1/2 VFULL SCALE
7
FIXED
SIGNAL
INTEGRATE
TIME
VARIABLE
REFERENCE
INTEGRATE
TIME
Figure 4. Basic Dual-Slope Converter
8
3-117
5 Page 
4-1/2 DIGIT
ANALOG-TO-DIGITAL CONVERTER
1
is disabled for one clock pulse at the beginning of the
reference integrate (deintegrate) phase. This one-count
delay compensates for the delay of the zero-crossing flip-
flop, and allows the correct number to be latched into the
display. Similarly, a one-count delay at the beginning of
auto-zero gives an overload display of 0000 instead of 0001.
No delay occurs during signal integrate, so true ratiometric
readings result.
Generating a Negative Supply
A negative voltage can be generated from the positive
supply by using a TC7660. (See Figure 9.)
TC7135
V+ 11
V – 1 (–5V)
TC7135
10 µF
+
24
+5V
8
5
TC7660
4+
10 µF
2
3
2
3
Figure 9. Negative Supply Voltage Generator
TYPICAL APPLICATIONS
RC Oscillator Circuit
R2
C
R1
GATES ARE 74C04
fO
1. fO ≈
1
2 C[0.41 RP + 0.70 R1]
, RP =
R1 R2
R1 + R2
a. If R = R1 = R2, f ≅ 0.55/RC
b. If R2 >> R1, f ≅ 0.45/R1C
c. If R2 << R1, f ≅ 0.72/R1C
2. Examples:
a. f = 120 kHz, C = 420 pF
R1 = R2 ≈ 10.9 kΩ
b. f = 120 kHz, C = 420 pF, R2 = 50 kΩ
R1 = 8.93 kΩ
c. f = 120 kHz, C = 220 pF, R2 = 5 kΩ
R1 = 27.3 kΩ
Comparator Clock Circuit
+5V
4
0.22 µF
16 kΩ
56 kΩ
1 kΩ
16 kΩ
2+ 8
LM311
3– 1
4
7
VOUT
30 kΩ
390 pF
R2
100 kΩ
+5V R4
2 kΩ
R2
100 kΩ
C1
0.1 µF
2+ 6
LM311
3– 4
1
C2
10 pF
7
VOUT
R3
50 kΩ
5
6
7
TELCOM SEMICONDUCTOR, INC.
8
3-123
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet TC7135.PDF ] | |
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