ADM231LAQ

Overview

The ADM231LAQ is a CMOS RS-232 line transceiver designed for EIA-232-E and V.28 communication interfaces. It features two drivers and two receivers, operating from dual power supplies: VCC at 5 V ± 10% and V+ ranging from 7.5 V to 13.2 V. The device utilizes an internal charge pump to generate a negative supply voltage (V–) from the V+ input. It supports data rates up to 120 kbps with a typical output voltage swing of ±9 V under a 3 kΩ load. The component is housed in a 14-pin Ceramic Dual In-Line Package (CERDIP) and operates within an industrial temperature range of -40°C to +85°C.

Feature Summary

• Integrated charge pump generates negative supply voltage from external positive input
• Schmitt trigger inputs provide noise immunity on receiver channels
• Internal pull-up resistors on transmitter inputs simplify unused pin handling
• High impedance receiver outputs facilitate bus sharing

Applications

• Industrial control systems requiring RS-232 connectivity
• Battery-powered equipment utilizing available positive supply rails
• Printers and peripheral devices interfacing with host computers
• Instruments and modems operating in electrically noisy environments

Procurement Notes

Verify that the ordering suffix 'A' corresponds to the industrial temperature grade (-40°C to +85°C) as defined by Analog Devices. Confirm the package type matches the required 14-pin CERDIP footprint. Ensure the design accommodates the specific requirement for an external V+ supply between 7.5 V and 13.2 V, distinct from standard single-supply variants.

Selection Notes

Select this part when a single 5 V digital logic supply is unavailable or when a higher positive rail exists for the charge pump. Unlike the ADM232L which requires four capacitors for a full dual-rail generation from 5 V, the ADM231L uses only two capacitors but mandates an external V+ source. This configuration reduces component count while maintaining compatibility with existing system power architectures.

Part Context

The ADM231LAQ belongs to the ADM2xxL family of enhanced CMOS RS-232 transceivers. This series improves upon the legacy AD2xx family by offering lower power consumption, faster slew rates, and support for smaller 1 µF capacitors. The 'L' designation indicates low-power CMOS technology optimized for reduced dissipation compared to earlier bipolar implementations.

Replacement Considerations

The ADM232L serves as a functional alternative if a single 5 V supply is preferred, though it requires four external capacitors instead of two. The ADM239L offers similar dual-supply operation but includes five receivers and three drivers. Verify pinout compatibility and capacitor requirements before substituting.