ISL8491IP RS422/RS485 Transceiver Equivalent & Substitute Parts

Part Overview

The ISL8491IP is a 1/1 full-duplex RS422/RS485 transceiver manufactured by Renesas Electronics Corporation in a 14-DIP package. This part is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production support. The ISL8491IP operates across a 4.5V to 5.5V supply range with a maximum data rate of 5Mbps and receiver hysteresis of 70mV, designed for industrial communication applications requiring robust differential signaling.

Key Parameters

Parameter	ISL8491IP
Manufacturer	Renesas Electronics Corporation
Type	Transceiver, Full-Duplex
Protocol	RS422, RS485
Number of Drivers/Receivers	1/1
Data Rate	5Mbps
Receiver Hysteresis	70mV
Voltage Supply	4.5V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Package/Case	14-DIP (0.300", 7.62mm)
Mounting Type	Through Hole
Product Status	Obsolete
RoHS Status	RoHS non-compliant

Substitute Part Grouping Explanation

Substitution for the ISL8491IP is determined by strict adherence to the following electrical and mechanical parameters:

Primary Substitution Criteria:

Protocol compatibility: RS422/RS485 full-duplex operation
Package compatibility: 14-DIP (0.300", 7.62mm) through-hole mounting
Driver/Receiver configuration: 1/1 transceiver
Supply voltage range: Must accommodate 4.5V to 5.5V operation
Operating temperature range: Must support -40°C to 85°C minimum
Data rate capability: Must support 5Mbps or higher

Secondary Compatibility Factors:

Receiver hysteresis: 70mV (ISL8491IP specification)
Mounting type: Through-hole DIP package
Moisture sensitivity level: 1 (Unlimited)

Substitute parts are grouped based on their ability to meet these criteria while offering active product status and improved compliance certifications where applicable.

Parameter Comparison

Part Number	Manufacturer	Protocol	Data Rate	Receiver Hysteresis	Voltage Supply	Operating Temp	Package	Product Status	RoHS Status
ISL8491IP	Renesas	RS422, RS485	5Mbps	70mV	4.5V ~ 5.5V	-40°C ~ 85°C	14-DIP	Obsolete	Non-compliant
MAX491EPD+	Analog Devices/Maxim	RS422, RS485	2.5Mbps	70mV	4.75V ~ 5.25V	-40°C ~ 85°C	14-DIP	Active	ROHS3 Compliant
MAX491CPD+	Analog Devices/Maxim	RS422, RS485	2.5Mbps	70mV	4.75V ~ 5.25V	0°C ~ 70°C	14-DIP	Active	ROHS3 Compliant
LT1791AIN#PBF	Analog Devices	RS422, RS485	250kbps	20mV	4.75V ~ 5.25V	-40°C ~ 85°C	14-DIP	Active	ROHS3 Compliant
LT1791AHN#PBF	Analog Devices	RS422, RS485	250kbps	20mV	4.75V ~ 5.25V	-40°C ~ 125°C	14-DIP	Active	ROHS3 Compliant
LT1791ACN#PBF	Analog Devices	RS422, RS485	250kbps	20mV	4.75V ~ 5.25V	0°C ~ 70°C	14-DIP	Active	ROHS3 Compliant
LT1791HN#PBF	Analog Devices	RS422, RS485	250kbps	20mV	4.75V ~ 5.25V	-40°C ~ 125°C	14-DIP	Active	ROHS3 Compliant
MAX3083CPD+	Analog Devices/Maxim	RS422, RS485	500kbps	100mV	4.75V ~ 5.25V	0°C ~ 70°C	14-DIP	Active	ROHS3 Compliant
SN65LBC180AN	Texas Instruments	RS422, RS485	30Mbps	50mV	4.75V ~ 5.25V	-40°C ~ 85°C	14-DIP	Obsolete	ROHS3 Compliant

Engineering Selection Recommendations

Primary Substitutes (Highest Compatibility):

MAX491EPD+ is the closest functional equivalent to ISL8491IP. Both devices share identical receiver hysteresis (70mV), matching operating temperature range (-40°C to 85°C), and identical package configuration. MAX491EPD+ is actively manufactured with ROHS3 compliance, addressing the obsolescence and compliance limitations of the original part. Data rate reduction from 5Mbps to 2.5Mbps is acceptable for most RS422/RS485 applications operating below this threshold.

Secondary Substitutes (Temperature-Dependent Selection):

For applications requiring extended high-temperature operation beyond 85°C, LT1791AHN#PBF and LT1791HN#PBF extend the upper operating limit to 125°C. These parts maintain full RS422/RS485 protocol compatibility and active product status with ROHS3 compliance. The reduced data rate (250kbps) and lower receiver hysteresis (20mV) are suitable for lower-speed industrial communication networks.

For applications limited to 0°C to 70°C operating range, MAX491CPD+ and LT1791ACN#PBF provide cost-effective alternatives with active status and full compliance certifications.

Alternative for High-Speed Applications:

SN65LBC180AN from Texas Instruments offers the highest data rate capability (30Mbps) and is suitable for applications requiring bandwidth exceeding 5Mbps. This part is obsolete but maintains ROHS3 compliance and the required -40°C to 85°C operating range. The 50mV receiver hysteresis differs from the ISL8491IP specification but remains within acceptable RS422/RS485 operating margins.

Compliance Consideration:

All recommended active substitutes carry ROHS3 compliance certification, eliminating the RoHS non-compliance status of the original ISL8491IP. This addresses regulatory requirements for new designs and production transitions.

Frequently Asked Questions (FAQ)

Q: Can MAX491EPD+ directly replace ISL8491IP in existing designs?

A: MAX491EPD+ is pin-compatible and functionally equivalent for most applications. Both devices use 14-DIP through-hole packaging with identical pinout. The primary difference is data rate capability (2.5Mbps vs. 5Mbps). If your application operates below 2.5Mbps, substitution is straightforward. For applications requiring 5Mbps operation, SN65LBC180AN supports this bandwidth.

Q: What is the impact of different receiver hysteresis values?

A: Receiver hysteresis determines the voltage differential required to switch the receiver output. ISL8491IP specifies 70mV, while LT1791 series devices specify 20mV. Lower hysteresis (20mV) provides faster response to small signal changes but may increase susceptibility to noise. Higher hysteresis (70mV) provides greater noise immunity. Selection depends on your transmission line quality and noise environment. Both values are within RS422/RS485 specification tolerances.

Q: Are all substitute parts available in the same packaging?

A: Yes. All listed substitute parts use 14-DIP (0.300", 7.62mm) through-hole packaging, ensuring mechanical compatibility with existing PCB layouts and sockets. Tube packaging is standard for all active substitutes.

Q: Which substitute is best for new designs?

A: MAX491EPD+ is recommended for new designs requiring direct ISL8491IP replacement with active product status and ROHS3 compliance. For extended temperature applications, LT1791AHN#PBF or LT1791HN#PBF provide -40°C to 125°C operation. For high-speed applications exceeding 2.5Mbps, SN65LBC180AN supports up to 30Mbps.

Q: What is the supply voltage compatibility range?

A: ISL8491IP operates at 4.5V to 5.5V. Most active substitutes operate at 4.75V to 5.25V, a narrower range. Verify your power supply regulation meets the substitute part's voltage specification. For applications with loose voltage regulation, confirm the substitute part's tolerance before implementation.

Q: Are there any pin-compatibility concerns?

A: All listed parts maintain 14-DIP package pinout compatibility for RS422/RS485 transceiver function. Verify specific pin assignments in device datasheets before PCB layout to ensure correct signal routing, particularly for enable/disable control pins and differential pair connections.

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