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TC826
A/D CONVERTER WITH BAR GRAPH DISPLAY OUTPUT
FEATURES
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Bipolar A/D Conversion
2.5% Resolution
Direct LCD Display Drive
鈥楾hermometer鈥?Bar or Dot Display
40 Data Segments Plus Zero
Overrange Plus Polarity Indication
Precision On鈥揅hip Reference ................ 35ppm/
擄
C
Differential Analog Input
Low Input Leakage .......................................... 10pA
Display Flashes on Overrange
Display Hold Mode
Auto鈥揨ero Cycle Eliminates Zero Adjust
Potentiometer
9V Battery Operation
Low Power Consumption ............................ 1.1mW
20mV to 2.0 V Full鈥揝cale Operation
Non鈥揗ultiplexed LCD Drive for Maximum
Viewing Angle
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Temperature
0擄C to +70擄C
GENERAL DESCRIPTION
In many applications a graphical display is preferred
over a digital display. Knowing a process or system oper-
ates, for example, within design limits is more valuable than
a direct system variable readout. A bar or moving dot display
supplies information precisely without requiring further inter-
pretation by the viewer.
The TC826 is a complete analog鈥搕o鈥揹igital converter
with direct liquid crystal (LCD) display drive. The 40 LCD
data segments plus zero driver give a 2.5% resolution bar
display. Full鈥搒cale differential input voltage range extends
from 20mV to 2V. The TC826 sensitivity is 500碌v. A low drift
35 ppm/擄C internal reference, LCD backplane oscillator and
driver, input polarity LCD driver, and overrange LCD driver
make designs simple and low cost. The CMOS design
required only 125碌A(chǔ) from a 9V battery. In +5V systems a
TC7660 DC to DC converter can supply the 鈥?V supply. The
differential analog input leakage is a low 10pA.
Two display formats are possible. The BAR mode
display is like a 鈥榯hermometer鈥?scale. The LCD segment
driver that equals the input plus all below it are on. The DOT
mode activates only the segment equal to the input. In either
mode the polarity signal is active for negative input signals.
An overrange input signal causes the display to flash and
activates the overrange annunciator. A hold mode can be
selected that freezes the display and prevents updating.
The dual slope integrating conversion method with
auto鈥搝ero phase maximizes noise immunity and eliminates
zero鈥搒cale adjustment potentiometers. Zero鈥搒cale drift is a
low 5
碌V/擄C.
Conversion rate is typically 5 per second and
is adjustable by a single external resistor.
A compact, 0.5" square, flat package minimizes PC
board area. The high pin count LSI package makes multi-
plexed LCD displays unnecessary. Low cost, direct drive
LCD displays offer the widest viewing angle and are readily
available. A standard display is available now for TC826
prototyping work.
PIN CONFIGURATION
BAR/DOT
BAR 40
BAR 39
BAR 38
BAR 37
BAR 36
BAR 35
BAR 33
BAR 32
50
BAR 34
BAR 31
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48
47
46
45
44
43
42
41
NC
BAR 30
BAR 29
BAR 28
BAR 27
BAR 26
BAR 25
BAR 24
BAR 23
BAR 22
BAR 21
BAR 20
BAR 19
BAR 18
BAR 17
BAR 16
40
39
38
37
36
35
34
33
17
NC
18
BAR 1
19
BAR 2
20
BAR 3
21
BAR 4
22
BAR 5
23
BAR 6
24
BAR 7
25
BAR 8
26
BAR 9
27
BAR 10
28
BAR 11
29
BAR 12
30
BAR 13
31
BAR 14
32
BAR 15
POL 鈥?/div>
60
HOLD
TEST
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NC
ANALOG
COMMON
+IN
鈥?IN
REF IN
+
CREF
鈥?/div>
CREF
VDD
VBUF
CAZ
VINT
VSS
OSC1
OSC2
BP
BAR 0
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NC
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OR
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TC826CBU
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ORDERING INFORMATION
Part No.
TC826CBU
Package
64鈥揚in PFP
8
TC826-6
11/6/96
TELCOM SEMICONDUCTOR, INC.
3-171
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