LTC1387ISW#PBF

Drivers, Receivers, Transceivers Overview

The LTC1387ISW#PBF is a low-power reconfigurable CMOS bidirectional transceiver manufactured by Analog Devices Inc. It supports RS-232 and RS-485/RS-422 protocols, configurable via logic inputs to operate as two single-ended RS-232 ports or one differential RS-485 port. The device operates on a single 5V supply (4.75V to 5.25V) with an onboard charge pump generating boosted positive and negative supplies for RS-232 drivers. Key electrical parameters include a typical supply current of 7mA, reducing to 5µA in shutdown mode. It features a data rate up to 5MBd in fast slew mode or 150kBd in slow slew mode. The component is housed in a 20-lead plastic SW package and operates within a temperature range of -40°C to +85°C.

Drivers, Receivers, Transceivers Feature Summary

• Configurable interface supporting either two RS-232 single-ended ports or one RS-485 differential port
• Onboard charge pump generates required voltage swings from a single 5V supply using four external capacitors
• Logic-selectable fast and slow slew rates for RS-485 driver output transitions
• Integrated loopback mode enabling internal connection of driver outputs to receiver inputs for diagnostic self-testing

Drivers, Receivers, Transceivers Applications

• Point-of-sale terminals
• Software selectable multiprotocol interface ports
• Low power RS-485/RS-422/RS-232/EIA562 interfaces
• Cable repeaters
• Level translators

Drivers, Receivers, Transceivers Procurement Notes

Verify the specific ordering suffix against manufacturer documentation to confirm package type and temperature grade. Confirm that the required external components, specifically four 0.1µF monolithic ceramic capacitors for the charge pump, are included in the system design. Ensure input voltage levels remain within specified limits to prevent damage to the receiver inputs.

Drivers, Receivers, Transceivers Selection Notes

Select this component when a single-port solution capable of switching between RS-232 and RS-485 standards is required. Consider the onboard charge pump capability if avoiding dual polarity power supplies is a priority. Evaluate the thermal performance requirements, as the device includes thermal shutdown protection that activates at 150°C. Verify that the operating temperature range meets the environmental conditions of the intended application.

Drivers, Receivers, Transceivers Part Context

The LTC1387 belongs to the Analog Devices family of single-supply interface transceivers designed for flexible communication systems. It shares functional similarities with other configurable transceivers like the LTC1321/LTC1322 series but offers distinct integration of both RS-232 and RS-485 capabilities in a single package. This allows designers to reduce board space compared to using separate discrete transceiver chips for different protocols.

Drivers, Receivers, Transceivers Replacement Considerations

LTC1387IG#PBF

Drivers, Receivers, Transceivers FAQ

How does the SLEW pin affect RS-485 operation?

In RS-485 mode, the SLEW pin controls the driver slew rate. A high logic level selects the fast slew rate, supporting data rates up to 5MBd. A low logic level selects the slow slew rate, which reduces signal bandwidth to minimize reflections and EMI, supporting data rates up to 150kBd.

What is the function of the ON pin regarding power consumption?

The ON pin controls the charge pump activity. Keeping the ON pin high maintains charge pump activation regardless of the DXEN and RXEN states, allowing immediate driver/receiver enablement without waiting for stabilization. Setting ON, DXEN, and RXEN all low places the device in shutdown mode, reducing supply current to 5µA.

How is the loopback mode activated?

Loopback mode is activated by setting the ON, DXEN, and RXEN inputs high while setting the 485/232 select input low for RS-232 mode, or high for RS-485 mode. This internally connects the driver outputs back to the receiver inputs for self-test purposes.