Microchip Technology TC7129 General Description Manual

4-1/2 Digit Analog-to-Digital Converters with
Features
• Count Resolution: ±19,999
• Resolution on 200 mV Scale: 10µV
• True Differential Input and Reference
• Low Power Consumption: 500µA at 9V
• Direct LCD Driver for 4-1/2 Digits, Decimal Points,
Low Battery Indicator, and Continuity Indicator
• Overrange and Underrange Outputs
• Range Select Input: 10:1
• High Common Mode Rejection Ratio: 110 dB
• External Phase Compensation Not Required
Applications
• Full-Featured Multimeters
• Digital Measurement Devices
Device Selection Table
Package Pin
Code Layout
TC7129CPL Normal 40-Pin PDIP
TC7129CKW Formed 44-Pin PQFP
TC7129CLW – 44-Pin PLCC
Typical Application
20 19
21 22
 2004 Microchip Technology Inc.
On-Chip LCD Drivers
Temperature
Package
Range
0°C to +70°C
0°C to +70°C
0°C to +70°C
Low Battery
18 17 16 15 14 13 12 11 10 9
TC7129
23 24 25 26 27 28 29 30 31 32
*
0.1 µF
0.1
+
µF
1 µF
150 kΩ
10 kΩ
+
9V
–
V
General Description
The TC7129 is a 4-1/2 digit Analog-to-Digital Converter
(ADC) that directly drives a multiplexed Liquid Crystal
Display (LCD). Fabricated in high-performance, low-
power CMOS, the TC7129 ADC is designed specifi-
cally for high-resolution, battery-powered digital multi-
meter applications. The traditional dual-slope method
of A/D conversion has been enhanced with a succes-
sive integration technique to produce readings accu-
rate to better than 0.005% of full-scale and resolution
down to 10 µV per count.
The TC7129 includes features important to multimeter
applications. It detects and indicates low battery condi-
tion. A continuity output drives an annunciator on the
display and can be used with an external driver to sound
an audible alarm. Overrange and underrange outputs,
along with a range-change input, provide the ability to
create auto-ranging instruments. For snapshot read-
ings, the TC7129 includes a latch-and-hold input to
freeze the present reading. This combination of features
makes the TC7129 the ideal choice for full-featured
multimeter and digital measurement applications.
Continuity
V+
8 7 6 5 4 3 2 1
33 34 35 36 37 38 39 40
330 kΩ
20
0.1 µF
kΩ
V+
100 kΩ
*Note: RC network between pins 26 and 28 is not required.
+
IN
TC7129
5 pF
120 kHz
10 pF
DS21459C-page 1