TC7136 View Datasheet(PDF) - TelCom Semiconductor Inc => Microchip
Part Name
Description
Manufacturer
TC7136 Datasheet PDF : 12 Pages
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LOW POWER, 3-1/2 DIGIT
ANALOG-TO-DIGITAL CONVERTERS
1
TC7136
TC7136A
analog common is a very stable potential with excellent
temperature stability (typically 35 ppm/°c). for TC7136A
This potential can be used to generate the TC7136A's
reference voltage. An external voltage reference will be
unnecessary in most cases because of the 35 ppm/°C
temperature coefficient. See TC7136A Internal Voltage
Reference discussion.
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 through a 500Ω resistor. The TEST pin
load should not be more than 1 mA. See the Applications
Section for additional information on using TEST as a
negative digital logic supply.
If TEST is pulled high (to V+), all segments plus the
minus sign will be activated. DO NOT OPERATE IN THIS
MODE FOR MORE THAN SEVERAL MINUTES. With TEST
= V+, the LCD segments are impressed with a DC voltage
which will destroy the LCD.
TC7136A Internal Voltage Reference
The TC7136 analog common voltage temperature sta-
bility has been significantly improved (Figure 9). The "A"
version of the industry-standard TC7136 device allows
users to upgrade old systems and design new systems
without external voltage references. External R and C val-
ues do not need to be changed; however, noise perfor-
mance will be improved by increasing CAZ. (See Auto-Zero
Capacitor section.) Figure 10 shows analog common sup-
plying the necessary voltage reference for the TC7136/A.
200
180
GUARANTEED
160
MAXIMUM NO MAXIMUM
SPECIFIED
140
TYPICAL
120
100
GUARANTEED
80
MAXIMUM TYPICAL
60
40
TYPICAL
20
TC7136A
TC7136
ICL7136
0
Figure 9. Analog Common Temperature Coefficient
TELCOM SEMICONDUCTOR, INC.
9V
+
2
26
1
V–
V+
240 kΩ
TC7136
TC7136A
VR+EF 36
VREF
10 kΩ
3
VR– EF 35
ANALOG 32
COMMON
SET VREF = 1/2 VFULL SCALE
Figure 10. TC7136A Internal Voltage Reference Connection
4
APPLICATIONS INFORMATION
Liquid Crystal Display Sources
Several manufacturers supply standard LCDs to inter-
face with the TC7136A 3-1/2 digit analog-to-digital con-
verter.
Manufacturer Address/Phone
5 Representative
Part Numbers*
Crystaloid
Electronics
5282 Hudson Dr.
Hudson, OH 44236
216-655-2429
C5335, H5535,
T5135, SX440
AND
VGI, Inc.
720 Palomar Ave.
FE 0201, 0501
Sunnyvale, CA 94086 FE 0203, 0701
408-523-8200
FE 2201
1800 Vernon St. Ste. 2 I1048, I1126
6
Roseville, CA 95678
916-783-7878
Hamlin, Inc.
612 E. Lake St.
Lake Mills, WI 53551
414-648-2361
3902, 3933, 3903
*NOTE: Contact LCD manufacturer for full product listing/specifications.
Decimal Point and Annunciator Drive
7
The TEST pin is connected to the internally-generated
digital logic supply ground through a 500Ω resistor. The
TEST pin may be used as the negative supply for external
CMOS gate segment drivers. LCD annunciators for decimal
points, low battery indication, or function indication may be
8 added without adding an additional supply. No more than 1
mA should be supplied by the TEST pin: its potential is
approximately 5V below V+.
3-257
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