The ICL7129A/MAX7129 is a high‑precision 4½‑digit A/D converter that directly drives a multiplexed liquid‑crystal display. It uses a successive‑integration technique to achieve up to 19,999 count resolution on 2 V and 200 mV ranges, with low‑impedance differential inputs and true ratiometric operation.
The device includes on‑board LCD driver, low‑battery detection, continuity detection, over‑range/under‑range outputs, and a 10:1 range‑change input. Detailed electrical characteristics, pin assignments, and timing diagrams are provided for designers.
| Resolution | 19,999 counts |
|---|---|
| Input Bias Current | 10 pA max |
| Noise | 3 µV peak‑to‑peak |
| Supply Voltage Range | 4 V to 14 V |
| Clock Frequency | 120 kHz |
| Display Multiplex Rate | 100 Hz |
| Zero Input Reading | 0000 counts |
The ICL7129A provides a resolution of up to 19,999 counts.
The device detects and flags a LOW BATTERY condition and provides a visual indicator and logic‑level output.
DP4/OR goes high when the result exceeds +19,999, while DP3/UR goes high when the result is below +1,000.
A crystal frequency of 120 kHz is recommended for maximum normal‑mode rejection at 60 Hz.