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PDF TC835CBU Data sheet ( Hoja de datos )
| Número de pieza | TC835CBU | |
| Descripción | PERSONAL COMPUTER DATA ACQUISITION A/D CONVERTER | |
| Fabricantes | TelCom Semiconductor | |
| Logotipo |  |
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1
TC835
PERSONAL COMPUTER DATA ACQUISITION A/D CONVERTER
FEATURES
s Upgrade of Pin-Compatible TC7135, ICL7135,
MAX7135 and SI7135
s Guaranteed 200 kHz Operation
s Single 5V Operation With TC7660
s Multiplexed BCD Data Output
s UART and Microprocessor Interface
s Control Outputs for Auto-Ranging
s Input Sensitivity ............................................ 100 µV
s No Sample and Hold Required
APPLICATIONS
s Personal Computer Data Acquisition
s Scales, Panel Meters, Process Controls
s HP-IL Bus Instrumentation
ORDERING INFORMATION
Part No.
Package
Temperature
Range
TC835CBU
64-Pin PQFP
0°C to +70°C
TC835CKW
44-Pin PQFP
0°C to +70°C
TC835CPI
28-Pin Plastic DIP
0°C to +70°C
NOTE: Tape and reel available for 44-pin PQFP packages.
TYPICAL APPLICATION
GENERAL DESCRIPTION
The TC835 is a low-power, 4-1/2 digit (0.005% resolu-
tion), BCD analog-to-digital converter (ADC) that has been
characterized for 200 kHz clock rate operation. The five
conversions per second rate is nearly twice as fast as the
ICL7135 or TC7135. The TC835 (like the TC7135) does
not use the external diode-resistor roll-over error compen-
sation circuits required by the ICL7135.
The multiplexed BCD data output is perfect for interfac-
ing to personal computers. The low-cost, greater than 14-
bit high-resolution, and 100 µV sensitivity makes the TC835
exceptionally cost-effective.
Microprocessor-based data acquisition systems are
supported by the BUSY and STROBE outputs, along with
the RUN/HOLD input of the TC835. The overrange, under-
range, busy, and run/hold control functions and multiplexed
BCD data outputs make the TC835 the ideal converter for
µP-based scales and measurement systems and intelligent
panel meters.*
The TC835 interfaces with full-function LCD and LED
display decoder/drivers. The UNDERRANGE and
OVERRANGE outputs may be used to implement an auto-
ranging scheme or special display functions.
*See Application Notes 16 and 17 for microprocessor interface tech-
niques.
2
3
4
5
ADDRESS BUS
CONTROL
DATA BUS
+ 5V
PA0
PA1
PA2
6522
-VIA-
PA3
PA4
PA5
PA6
PA7
CA1
CA2
1Y 1B
2Y 2B
3Y 3B
SEL
157 1A
2A
3A
PB0 PB1 PB2
PB5
PB4
PB3
GAIN SELECTION fIN
V+ REF CAP
BUF
POL
AZ
OR INT
UR
D5
B8 TC835
B4 + INPUT
B2
B1
D1 VR
D2
D3 –INPUT
D4 ANALOG
STB COMMON
R/H
fIN
DGND
– 5V
GAIN: 10, 20, 50, 100
+15V –15V
11
83
10
LH0084 9
14
REF
VOLTAGE
16
15
DG529
CHANNEL 1
DA
DB
WR
A1 A0 EN
CHANNEL 2
CHANNEL 3
CHANNEL 4
DIFFERENTIAL
MULTIPLEXER
6
7
CHANNEL SELECTION
TELCOM SEMICONDUCTOR, INC.
TC835-8 11/5/96
3-65
8
1 page  
PERSONAL COMPUTER
DATA ACQUISITION A/D CONVERTER
1
TC835
SW I
+ IN
SW
–
RI
SW
+
RI
REF
IN
SWR
CREF
SWZ
ANALOG
COM
SW
+
RI
SW
–
RI
ANALOG
INPUT BUFFER
+
RINT
–
SWIZ SWZ
CINT
CSZ
–
+
SWZ
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 TC835 is a dual-slope, integrating analog-to-digital
converter. An understanding of the dual-slope conversion
technique will aid in following the detailed TC835 opera-
tional 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. Time is 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.
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).
For a constant VIN:
[ ]VIN = VR
tRI
t SI
.
TELCOM SEMICONDUCTOR, INC.
The dual-slope converter accuracy is unrelated to the
integrating resistor and capacitor values, as long as they are
stable during a measurement cycle. An inherent benefit is
noise immunity. Noise spikes are integrated, or averaged, to
zero during the 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
TC835 Operational Theory
The TC835 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 TC835 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.
3
4
ANALOG
INPUT
SIGNAL
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 4. Basic Dual-Slope Converter
7
8
3-69
5 Page 
PERSONAL COMPUTER
DATA ACQUISITION A/D CONVERTER
TYPICAL APPLICATIONS DIAGRAMS
4-1/2 Digit ADC With Multiplexed Common Anode LED Display +5V
1
TC835
2
20 19 18 17 12
0.33µF
4
1 µF
5
6
100 kΩ
200 kHz
22
100 kΩ
+
ANALOG
INPUT
–
10
1 µF
9
3
D1 D2 D3 D4 D5
INT OUT
AZ IN
BUFF
OUT
fIN
TC835
+INPUT
POL
C–REF
C+REF
–INPUT
ANALOG
COMMON
B8
B4
B2
B1
23
7
8
16
15
14
13
V–
REF
IN
V+
12
6.8 kΩ 11
4.7 kΩ
1 µF
–5V
100 kΩ
TC04
bc
BLANK MSD ON ZERO
6D
2
C
1
B
7A
7 7 77
X7
5 9–15
RBI
7447
16 +5V
RC Oscillator Circuit
R2 R1
C
fO
GATES ARE 74C04
1.
fO =
1 , RP =
2 C(0.41 RP + 0.7 R1)
R1 R2
R1 + R2
a. If R1 = R2 = R1, 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 Circuits
+5V
0.22 µF
16 kΩ
16 kΩ
56 kΩ
2+ 8
LM311
3– 1
4
7
1 kΩ
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
3
4
5
6
7
8
TELCOM SEMICONDUCTOR, INC.
3-75
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet TC835CBU.PDF ] | |
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