TC7107 TelCom, TC7107 Datasheet - Page 12

• Manufacturer Part Number: TC7107
• Description: 3-1/2 DIGIT A/D CONVERTERS
• Manufacturer: TelCom

TC7106
TC7106A
TC7107
TC7107A
DEVICE PIN FUNCTIONAL DESCRIPTION
Differential Signal Inputs
(V
inputs and accepts input signals within the input stage
common mode voltage range (V
–1.0 to V
the system when the TC7106A/TC7107A operates from a
battery or floating power source (isolated from measured
system) and V
See Figure 8.
86dB common-mode rejection ratio minimizes error. Com-
mon-mode voltages do, however, affect the integrator out-
put level. Integrator output saturation must be prevented. A
worst-case condition exists if a large positive V
conjunction with a full-scale negative differential signal. The
negative signal drives the integrator output positive along
with V
output swing can be reduced below the recommended 2.0V
3-194
+
TC7106A
TC7107A
IN
The TC7106A/7017A is designed with true differential
In systems where common-mode voltages exist, the
V +
CM
(a)
(Pin 31), V
V REF
V REF
–
(Figure 9). For such applications the integrator
+
–
+1 V. Common-mode voltages are removed from
IN
–
Figure 7. External Reference
is connected to analog common (V
V +
–
IN
V +
Figure 8. Common-Mode Voltage Removed in Battery Operation with V
6.8V
ZENER
SOURCE
POWER
(Pin 30))
V
I Z
–
GND
MEASURED
V +
V –
TC7106A
TC7107A
CM
SYSTEM
COMMON
). The typical range is V
V +
(b)
V REF
V REF
GND
+
–
20k
CM
V +
1.2V
REF
exists in
6.8k
TC04
V
ANALOG
COMMON
COM
V
V BUF
+
–
IN
IN
):
+
V REF
full-scale swing. The integrator output will swing within 0.3V
of V
Differential Reference
(V
within the V
common-mode voltages, C
stray node capacitance.
lower analog common temperature coefficient. This gives a
very stable voltage suitable for use as a reference. The
temperature coefficient of analog common is 20ppm/ C
typically.
Figure 9.
C AZ
–
TC7106A
+
REF
+
–
V
V
+
The reference voltage can be generated anywhere
To prevent rollover errors from being induced by large
The TC7106A/TC7107A circuits have a significantly
V REF
CM
IN
+
or V
V INT
(Pin 36), V
–
V +
Common-Mode Voltage Reduces Available Integrator
Swing. (V
without increasing linearity errors.
+
3-1/2 DIGIT A/D CONVERTERS
SEGMENT
+
+
–
to V
INPUT
BUFFER
DRIVE
9V
POL
Where:
–
OSC 1
OSC 3
OSC 2
V –
COM
power supply range.
IN
–
REF
–
BP
TELCOM SEMICONDUCTOR, INC.
= Analog Common
C
R
V
T
V
LCD DISPLAY
I
I
I
I
IN
(Pin 35))
R
=
=
=
=
)
REF
I
INTEGRATION TIME
INTEGRATION CAPACITOR
INTEGRATION RESISTOR
R I C I
should be large compared to
T I
[
–
+
C
V
CM
I
INTEGRATOR
–
V
IN
[
=
V
4000
f
I
OSC