TC7106 データシートの表示（PDF） - TelCom Semiconductor Inc => Microchip
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TC7106 Datasheet PDF : 19 Pages
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TC7106
TC7106A
TC7107
TC7107A
3-1/2 DIGIT A/D CONVERTERS
V+
VR+EF
VR– EF
TC7106A
TC7107A
(a)
V+
V+
6.8V
ZENER
IZ
V+
TC7106A
TC7107A
20kΩ
VR+EF
VR– EF
COMMON
(b)
6.8kΩ
TC04
1.2V
REF
Figure 7. External Reference
DEVICE PIN FUNCTIONAL DESCRIPTION
Differential Signal Inputs
(V+IN (Pin 31), V–IN (Pin 30))
The TC7106A/7017A is designed with true differential
inputs and accepts input signals within the input stage
common mode voltage range (VCM). The typical range is V+
–1.0 to V– +1 V. Common-mode voltages are removed from
the system when the TC7106A/TC7107A operates from a
battery or floating power source (isolated from measured
system) and VI–N is connected to analog common (VCOM):
See Figure 8.
In systems where common-mode voltages exist, the
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 VCM exists in
conjunction with a full-scale negative differential signal. The
negative signal drives the integrator output positive along
with VCM (Figure 9). For such applications the integrator
output swing can be reduced below the recommended 2.0V
+
VIN
–
VCM
INPUT
BUFFER
+
RI
–
CI
–
+
VI
INTEGRATOR
[ VI =
Where:
TI
RI CI
VCM – VIN
TI
= INTEGRATION TIME
=
4000
fOSC
CI = INTEGRATION CAPACITOR
RI = INTEGRATION RESISTOR
Figure 9. Common-Mode Voltage Reduces Available Integrator
Swing. (VCOM ≠ VIN)
full-scale swing. The integrator output will swing within 0.3V
of V+ or V– without increasing linearity errors.
Differential Reference
(V
+
REF
(Pin
36),
VR–EF
(Pin
35))
The reference voltage can be generated anywhere
within the V+ to V– power supply range.
To prevent rollover errors from being induced by large
common-mode voltages, CREF should be large compared to
stray node capacitance.
The TC7106A/TC7107A circuits have a significantly
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.
SEGMENT
DRIVE
LCD DISPLAY
3-194
MEASURED
SYSTEM
V+
V– GND
V+ V– GND
POWER
SOURCE
VBUF
V+IN
CAZ VINT
V –IN
TC7106A
ANALOG
COMMON
VRE– F
VR+ EF
V+
POL BP
OSC1
OSC3
OV –SC2
+
9V
Figure 8. Common-Mode Voltage Removed in Battery Operation with VI–N = Analog Common
TELCOM SEMICONDUCTOR, INC.
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