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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 Converter | |
| Fabricantes | Microchip | |
| Logotipo |  |
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TC7136/TC7136A
Low Power 3-1/2 Digit Analog-to-Digital Converter
Features
• Fast Over Range Recovery, Ensured First Reading
Accuracy
• Low Temperature Drift Internal Reference
- TC7136: 70ppm/°C (Typ.)
- TC7136A: 35ppm/°C (Typ.)
• Zero Reading with Zero Input
• Low Noise: 15µVP-P
• High Resolution: 0.05%
• Low Input Leakage Current: 1pA (Typ.)/10pA (Max.)
• Precision Null Detectors with True Polarity at Zero
• High-Impedance Differential Input
• Convenient 9V Battery Operation with Low Power
Dissipation: 500µW (Typ.)/900µW (Max.)
Applications
• Thermometry
• Bridge Readouts: Strain Gauges, Load Cells,
Null Detectors
• Digital Meters: Voltage/Current/Ohms/Power, pH
• Digital Scales, Process Monitors
• Portable Instrumentation
Device Selection Table
Part Number
TC7136 CPI
TC7136 CKW
TC7136 CLW
TC7136A CPI
TC7136A CKW
TC7136A CLW
Package
40-Pin PDIP
44-Pin PQFP
44-Pin PLCC
40-Pin PDIP
44-Pin PQFP
44-Pin PLCC
Temperature
Range
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
General Description
The TC7136 and TC7136A are low power, 3-1/2 digit
with liquid crystal display (LCD) drivers and analog-to-
digital converters. These devices incorporate an "inte-
grator output zero" phase, which enables over range
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 com-
mon temperature drift to 35ppm/°C (typical) and
75ppm/°C (maximum). This represents an improve-
ment of two to four times over similar 3-1/2 digit con-
verters. The costly, space consuming external
reference source may be removed.
The TC7136 and TC7136A limit linearity error to less
than 1 count on 200mV or 2V full scale ranges. The roll-
over error (the difference in readings for equal magni-
tude, but opposite polarity input signals) is below ±1
count. High-impedance differential inputs offer 1pA
leakage currents and a 1012Ω input impedance. The
differential reference input allows ratiometric measure-
ments for ohms or bridge transducer measurements.
The 15µVP-P noise performance ensures a "rock solid"
reading. The auto-zero cycle enables a zero display
readout for a 0V input.
© 2002 Microchip Technology Inc.
DS21461B-page 1
1 page  
TC7136/TC7136A
1.0 ELECTRICAL
CHARACTERISTICS
Absolute Maximum Ratings*
Supply Voltage (V+ to V-)....................................... 15V
Analog Input Voltage (Either Input) (Note 1)... V+ to V-
Reference Input Voltage (Either Input)............ V+ to V-
Clock Input .................................................TEST to V+
Package Power Dissipation (TA ≤ 70°C) (Note 2):
Plastic DIP ................................................... 1.23W
Plastic Quad Flat Package .......................... 1.00W
PLCC ........................................................... 1.23W
Operating Temperature Range:
C Devices.......................................... 0°C to +70°C
I Devices ........................................ -25°C to +85°C
Storage Temperature Range .............. -65°C to +150°C
*Stresses above those listed under "Absolute Maximum
Ratings" may cause permanent damage to the device. These
are stress ratings only and functional operation of the device
at these or any other conditions above those indicated in the
operation sections of the specifications is not implied.
Exposure to Absolute Maximum Rating conditions for
extended periods may affect device reliability.
TC7136 AND TC7136A ELECTRICAL SPECIFICATIONS
Electrical Characteristics: VS = 9V, fCLK = 16kHz, and TA = +25°C, unless otherwise noted.
Symbol
Parameter
Min
Typ
Max
Unit
Test Conditions
Input
Zero Input Reading
-000.0
±000.0 +000.0 Digital VIN = 0V, Full Scale = 200mV
Reading
Zero Reading Drift
Ratiometric Reading
— 0.2
1 µV/°C VIN = 0V, 0°C ≤ TA ≤ +70°C
999 999/1000 1000 Digital VIN = VREF, VREF = 100mV
Reading
NL Non-Linearity Error
— 1 ±0.2 Count Full Scale = 20mV or 2V Max.
Deviation from best Straight Line
ER
eN
IL
CMRR
TCSF
Rollover Error
Noise
Input Leakage Current
Common Mode Rejection Ratio
Scale Factor Temperature
Coefficient
-1
—
—
—
—
-1 ±0.2 1 Count VIN- = VIN+ ≈ 200mV
15 — µVP-P VIN = 0V, Full Scale = 200mV
1 10 pA VIN = 0V
50 — µV/V VCM = ±1V, VIN = 0V, Full Scale = 200mV
1 5 ppm/°C VIN = 199mV, 0°C ≤ TA ≤ +70°C
Ext. Ref. Temp. Coeff. = 0ppm/°C
Note 1: Input voltages may exceed supply voltages when input current is limited to 100µA.
2: Dissipation rating assumes device is mounted with all leads soldered to PC board.
3: Refer to "Differential Input" discussion.
4: Backplane drive is in phase with segment drive for "OFF" segment and 180° out-of-phase for "ON" segment. Frequency
is 20 times conversion rate. Average DC component is less than 50mV.
5: See "Typical Application".
6: A 48kHz oscillator increases current by 20µA (typical). Common current not included.
© 2002 Microchip Technology Inc.
DS21461B-page 5
5 Page 
5.0 DIGITAL SECTION
The TC7136/A contains all the segment drivers neces-
sary to directly drive a 3-1/2 digit LCD. An LCD back-
plane driver is included. The backplane frequency is
the external clock frequency divided by 800. For three
conversions per second, the backplane frequency is
60Hz with a 5V nominal amplitude. When a segment
driver is in phase with the backplane signal, the seg-
ment is OFF. An out-of-phase segment drive signal
causes the segment to be ON, or visible. This AC drive
configuration results in negligible DC voltage across
each LCD segment, ensuring long LCD life. The polar-
ity segment driver is ON for negative analog inputs. If
VIN+ and VIN- are reversed, this indicator would
reverse.
On the TC7136/A, when the TEST pin is pulled to V+,
all segments are turned ON. The display reads -1888.
During this mode, the LCD segments have a constant
DC voltage impressed.
Note:
Do not leave the display in this mode for
more than several minutes. LCDs may be
destroyed if operated with DC levels for
extended periods.
The display font and segment drive assignment are
shown in Figure 5-1.
FIGURE 5-1:
DISPLAY FONT AND
SEGMENT ASSIGNMENT
Display Font
1000's 100's
10's
1's
5.1 System Timing
The oscillator frequency is divided by 4 prior to clocking
the internal decade counters. The four-phase mea-
surement cycle takes a total of 4000 counts, or 16,000
clock pulses. The 4000 count cycle is independent of
input signal magnitude.
© 2002 Microchip Technology Inc.
TC7136/TC7136A
Each phase of the measurement cycle has the
following length:
1. Auto-zero phase: 3000 to 2900 counts
(1200 to 11,600 clock pulses)
2. Signal integrate: 1000 counts
(4000 clock pulses)
This time period is fixed. The integration period is:
EQUATION 5-1:
Where:
tSI
=
4000
1
FOSC
FOSC is the externally set clock frequency.
3. Reference integrate: 0 to 2000 counts
4. Zero integrator: 11 to 640 counts
The TC7136 is a drop-in replacement for the TC7126
and ICL7126. The TC7136A offers a greatly improved
internal reference temperature coefficient. Minor com-
ponent value changes are required to upgrade existing
designs and improve the noise performance.
6.0 COMPONENT VALUE
SELECTION
6.1 Auto-Zero Capacitor (CAZ)
The CAZ capacitor size has some influence on system
noise. A 0.47µF capacitor is recommended for 200mV
full scale applications, where 1LSB is 100µV. A 0.1µF
capacitor is adequate for 2V full scale applications. A
Mylar type dielectric capacitor is adequate.
6.2 Reference Voltage Capacitor
(CREF)
The reference voltage, used to ramp the integrator out-
put voltage back to zero during the reference integrate
phase, is stored on CREF. A 0.1µF capacitor is accept-
able when VREF- is tied to analog common. If a large
Common mode voltage exists (VREF- ≠ analog com-
mon) and the application requires a 200mV full scale,
increase CREF to 1µF. Rollover error will be held to less
than 0.5 count. A Mylar type dielectric capacitor is
adequate.
6.3 Integrating Capacitor (CINT)
CINT should be selected to maximize integrator output
voltage swing without causing output saturation. Ana-
log common will normally supply the differential voltage
reference in this case, a ±2V full scale integrator output
swing is satisfactory. For 3 readings per second
(FOSC = 48kHz), a 0.047µF value is suggested. For
one reading per second, 0.15µF is recommended. If a
different oscillator frequency is used, CINT must be
changed in inverse proportion to maintain the nominal
±2V integrator swing.
DS21461B-page 11
11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet TC7136.PDF ] | |
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