TC7106ACKW Microchip Technology, TC7106ACKW Datasheet - Page 8

• Manufacturer Part Number: TC7106ACKW
• Description: IC ADC 3 1/2DGT LCD DVR 44-MQFP
• Manufacturer: Microchip Technology

Specifications of TC7106ACKW

• Display Type: LCD
• Configuration: 7 Segment
• Digits Or Characters: A/D 3.5 Digits
• Current - Supply: 800µA
• Voltage - Supply: 9V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 44-MQFP, 44-PQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Interface: -

TC7106/A/TC7107/A
3.0
(All Pin designations refer to 40-Pin PDIP.)
3.1
The TC7106A and TC7107A are dual slope, integrating
Analog-to-Digital Converters. An understanding of the
dual slope conversion technique will aid in following the
detailed operation theory.
The conventional dual slope converter measurement
cycle has two distinct phases:
• Input Signal Integration
• Reference Voltage Integration (De-integration)
The input signal being converted is integrated for a
fixed time period (T
clock pulses. An opposite 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 (T
Figure
FIGURE 3-1:
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.
EQUATION 3-1:
DS21455D-page 8
Where:
T
T
V
SI
RI
R
Analog
Signal
Voltage
Input
3-1.
REF
Integrate
DETAILED DESCRIPTION
Dual Slope Conversion Principles
=
=
=
+/–
Signal
Fixed
Time
Reference voltage
Signal integration time (fixed)
Reference voltage integration time
(variable).
------- -
RC
Polarity Control
1
Variable
Reference
Integrate
Time
∫
DISPLAY
T
0
SI
SI
Switch
Driver
Integrator
). Time is measured by counting
V
–
+
Basic Dual Slope Converter.
IN
V
V
t ( )dt
C
IN
Phase
Control
IN
µ V
µ
1/2
REF
=
V
–
+
Comparator
REF
V
-------------- -
RC
Control
R
Logic
T
RI
Counter
RI
). See
For a constant V
EQUATION 3-2:
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
approximation converters in high noise environments.
Interfering signals with frequency components at
multiples of the averaging period will be attenuated.
Integrating ADCs commonly operate with the signal
integration period set to a multiple of the 50/60Hz
power line period (see
FIGURE 3-2:
Dual Slope Converter.
Where:
F
20
10
30
R
V
OSC
V
0
INT
INT
FS
0.1/T
=
=
=
=
C
INT
errors
Clock Frequency at Pin 38
Full Scale Input Voltage
Integrating Resistor
Desired Full Scale Integrator Output
Swing
IN
:
=
V
(
----------------------------------------------------- -
IN
4000
Normal Mode Rejection of
Input Frequency
Figure
= V
© 2008 Microchip Technology Inc.
that
)
R
⎛
⎝
1/T
------------ -
F
V
T = Measured Period
3-2).
T
T
OSC
1
INT
RI
SI
plague
⎞ V
⎠
⎛
⎝
-----------
R
INT
FS
⎞
⎠
successive
10/T