ADM231LAR

Overview

The ADM231LAR is a 5 V-powered CMOS RS-232 driver/receiver from Analog Devices, featuring two drivers and two receivers. It requires external power supplies of 7.5 V to 13.2 V for the positive rail (V+) and generates a negative supply (V-) internally via a charge pump. The device operates at data rates up to 120 kbps and meets EIA-232-E specifications with ±9 V output swings. It utilizes small 1 µF capacitors for voltage conversion and includes internal pull-up resistors on inputs. Available in 14-pin PDIP and SOIC packages, it supports industrial temperature ranges.

Feature Summary

• Integrates charge pump circuitry to generate required RS-232 voltage levels from standard logic supplies
• Provides Schmitt trigger receiver inputs to ensure noise immunity and error-free reception
• Includes internal pull-up and pull-down resistors on all input pins to simplify interface design
• Features latch-up free construction for enhanced reliability under varying operating conditions

Applications

• Computers
• Peripherals
• Modems
• Printers
• Instruments

Procurement Notes

Verify that the specific ordering suffix corresponds to the desired package type and temperature range. Confirm whether the 'L' variant indicates lead-free compliance or specific mechanical dimensions as defined by the manufacturer's current documentation. Ensure compatibility with existing board layouts regarding pin configurations and capacitor placement requirements.

Selection Notes

Select this component when a dual-channel RS-232 interface is required without onboard positive voltage generation. It is suitable for systems where a separate positive supply rail between 7.5 V and 13.2 V is already available. Consider alternative family members if onboard charge pumps for both polarities or shutdown capabilities are necessary for the application.

Part Context

The ADM231LAR belongs to the ADM2xxL family of line drivers and receivers designed for EIA-232-E and V.28 communications interfaces. This family addresses applications where 12 V supplies are unavailable by utilizing single 5 V digital supplies alongside other rails. The ADM231L specifically serves as a foundational model within this series, offering basic driver and receiver functionality with minimal external component requirements.

Replacement Considerations

ADM231L

FAQ

Does the ADM231LAR include an onboard positive voltage converter?

No, the ADM231LAR does not include an onboard positive voltage converter. It requires an external positive supply voltage ranging from 7.5 V to 13.2 V connected to the V+ pin.

What is the function of the internal resistors on the input pins?

Each TTL/CMOS input has an internal 400 kΩ pull-up resistor to VCC, and each RS-232 input has an internal 5 kΩ pull-down resistor to GND. These ensure defined logic states when inputs are unconnected.

Is the ADM231LAR compatible with microprocessor buses requiring high impedance states?

No, the ADM231LAR lacks an Enable (EN) or Shutdown (SD) pin. Consequently, its outputs cannot be placed in a high impedance state, making it unsuitable for direct connection to shared microprocessor data buses compared to variants like the ADM236L or ADM241L.