3.5-digit ADC in a 40-pin DIP
The MAX138CPL+ is a 3.5-digit analog-to-digital converter (ADC) from Analog Devices, packaged in a 40-lead PDIP (0.600-inch body width). It integrates the ADC core, display drivers, and reference onto a single chip — a legacy workhorse for panel-meter and data-acquisition designs that need a direct digital readout without an external microcontroller. With two input channels and a single-supply range of 2.5 V to 7 V, it handles ratiometric measurements from bridge sensors or potentiometers.
Package and supply rails
The 40-pin PDIP (0.600-inch row spacing) is a through-hole package — it protrudes through the board and requires a wave-solder or hand-solder step. No MSL floor-life concern: the PDIP body is moisture-insensitive, so no bake-out before assembly even after extended storage. Supply voltage spans 2.5 V to 7 V, single supply only. The 3.5-digit resolution (~±1999 count full scale) is typical for a dual-slope integrating ADC — the integration period rejects 50/60 Hz line noise when the clock is set to an integer multiple of the mains period.