TC7107ACKW View Datasheet(PDF) - Microchip Technology
Part Name
Description
Manufacturer
TC7107ACKW Datasheet PDF : 34 Pages
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TC7106/A/TC7107/A
Segment
Drive
LCD Display
Measured
System
V+
V-
GND
V+ V- GND
Power
Source
V BUF
VIN +
VIN -
Analog
Common
C AZ VINT
TC7106A
VREF - VREF+ V+
POL BP
OSC1
OSC3
OSC2
V-
+
9V
FIGURE 8-2:
Common Mode Voltage Removed in Battery Operation with VIN- = Analog Common.
The analog common pin serves to set the analog section
reference or common point. The TC7106A is specifically
designed to operate from a battery, or in any
measurement system where input signals are not
referenced (float), with respect to the TC7106A power
source. The analog common potential of V+ – 3.0V gives
a 6V end of battery life voltage. The common potential
has a 0.001% voltage coefficient and a 15Ω output
impedance.
With sufficiently high total supply voltage (V+ – V- >
7.0V), analog common is a very stable potential with
excellent temperature stability, typically 20 ppm/°C.
This potential can be used to generate the reference
voltage. An external voltage reference will be
unnecessary in most cases because of the 50 ppm/°C
maximum temperature coefficient. See Section 8.5
“Internal Voltage Reference”.
8.4 TEST (Pin 37)
The TEST pin potential is 5V less than V+. TEST may
be used as the negative power supply connection for
external CMOS logic. The TEST pin is tied to the
internally generated negative logic supply (Internal
Logic Ground) through a 500Ω resistor in the
TC7106A. The TEST pin load should be no more than
1 mA.
If TEST is pulled to V+ all segments plus the minus sign
will be activated. Do not operate in this mode for more
than several minutes with the TC7106A. With
TEST = V+, the LCD segments are impressed with a
DC voltage which will destroy the LCD.
The TEST pin will sink about 10 mA when pulled to V+.
8.5 Internal Voltage Reference
The analog common voltage temperature stability has
been significantly improved (Figure 8-3). The “A”
version of the industry standard circuits allow users to
upgrade old systems and design new systems without
external voltage references. External R and C values
do not need to be changed. Figure 8-4 shows analog
common supplying the necessary voltage reference for
the TC7106A/TC7107A.
200
180 No Maximum Specified
160
140
120
No
100
Maximum
Maximum Specified
80
Limit
Typical
60
40
Typical
20
0
TC
7106A
ICL7106
No
Maximum
Specified
Typical
ICL7136
FIGURE 8-3:
Analog Common
Temperature Coefficient.
1
V-
V+
TC7106A
TC7107A
VREF + 36
VREF
VREF - 35
Analog 32
Common
Set VREF = 1/2 VFULL SCALE
24kΩ
1kΩ
FIGURE 8-4:
Connection.
Internal Voltage Reference
© 2008 Microchip Technology Inc.
DS21455D-page 17
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