ADM239LJRZ

Overview

The ADM239LJRZ is a CMOS RS-232 transceiver from Analog Devices, designed for EIA-232-E and V.28 interfaces. It features three drivers and five receivers in a 24-pin package. The device operates with a 5 V supply (VCC) and requires an external 7.5 V to 13.2 V supply (V+) for its internal charge pump, which generates the negative voltage rail. It supports data rates up to 120 kbps and includes a low-power shutdown mode drawing ≤1 µA. Key electrical parameters include ±9 V output swing, ±30 V receiver input protection, and Schmitt trigger inputs with 0.65 V hysteresis.

Feature Summary

• Integrates a single negative charge pump converter requiring only two external capacitors
• Provides active-low enable control for high-impedance receiver outputs
• Features Schmitt trigger inputs to ensure noise immunity on slow signals
• Includes internal pull-up and pull-down resistors on logic inputs

Applications

• Battery-powered equipment requiring low power consumption
• Systems utilizing available +12 V auxiliary supplies
• Microprocessor systems sharing common data lines
• Industrial instruments and peripherals

Procurement Notes

Verify the specific suffix 'JRZ' against the manufacturer's current ordering guide to confirm the exact package type and temperature grade. Confirm that the design accommodates the required external 7.5 V to 13.2 V supply voltage, as this part differs from standard single-supply variants.

Selection Notes

Select the ADM239LJRZ when a system has an available positive supply between 7.5 V and 13.2 V but lacks a negative rail. This component reduces external component count compared to older generations while providing five receiver channels. Ensure the application utilizes the enable pin for bus sharing or power management.

Part Context

This component belongs to the ADM2xxL family of line drivers and receivers. Unlike most members of this series that generate both positive and negative voltages from a single 5 V source, the ADM239L relies on an external positive supply to drive its internal charge pump. It serves as an enhanced upgrade to the legacy AD2xx series with improved power efficiency.

Replacement Considerations

ADM231L

FAQ

Why does the ADM239L require an external V+ supply?

Unlike other parts in the ADM2xxL family, the ADM239L contains only a negative charge pump converter. It requires an external positive supply ranging from 7.5 V to 13.2 V to generate the necessary negative voltage for RS-232 signaling.

How does the Enable (EN) pin function?

The EN pin is active low. When driven low, the receiver outputs are enabled. When driven high, the outputs enter a high-impedance state, allowing multiple devices to share a common data line without interference.

What is the purpose of the internal pull-up resistor on transmitter inputs?

Each TTL/CMOS transmitter input has an internal 400 kΩ pull-up resistor to VCC. This ensures that unused inputs default to a high state, forcing the corresponding RS-232 outputs into a safe low state.