ISO35MDWR RS422/RS485 Digital Isolator Equivalent & Substitute Parts

Part Overview

The ISO35MDWR is a Texas Instruments RS422/RS485 digital isolator rated for 2500Vrms isolation with 3 channels, 1Mbps data rate, and 25kV/µs common mode transient immunity. The device is packaged in 16-SOIC surface mount and operates across -55°C to 125°C. This part is designated Last Time Buy status, making identification of functionally equivalent alternatives necessary for design continuity and long-term supply planning.

Substiute Parts

ISO35MDWR

Texas InstrumentsIn Stock: 1421ISO35MDWR Datasheet

Current PartRFQ

ISO1412DWR

Texas InstrumentsIn Stock: 1368ISO1412DWR Datasheet

MFR RecommendedRFQ

MAX14945EWE+

Analog Devices Inc./Maxim IntegratedIn Stock: 1183MAX14945EWE+ Datasheet

MFR RecommendedRFQ

MAX14945EWE+T

Analog Devices Inc./Maxim IntegratedIn Stock: 1107MAX14945EWE+T Datasheet

MFR RecommendedRFQ

MAX14948EWE+

Analog Devices Inc./Maxim IntegratedIn Stock: 2501MAX14948EWE+ Datasheet

MFR RecommendedRFQ

MAX14948EWE+T

Analog Devices Inc./Maxim IntegratedIn Stock: 27967MAX14948EWE+T Datasheet

MFR RecommendedRFQ

MAX14949EWE+

Analog Devices Inc./Maxim IntegratedIn Stock: 1268MAX14949EWE+ Datasheet

MFR RecommendedRFQ

MAX14949EWE+T

Analog Devices Inc./Maxim IntegratedIn Stock: 3442MAX14949EWE+T Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility is determined by the following critical parameters:

Mandatory Compatibility Criteria:

• Package type: 16-SOIC (0.295", 7.50mm Width)
• Protocol support: RS422/RS485
• Channel configuration: 3 channels with 2/1 input distribution
• Isolation technology: Capacitive coupling
• RoHS3 compliance

Performance Considerations:

• Isolation voltage rating (minimum 2500Vrms required)
• Data rate capability (minimum 1Mbps required)
• Common mode transient immunity (minimum 25kV/µs required)
• Supply voltage compatibility
• Operating temperature range coverage

Substitute parts are grouped into two categories based on isolation voltage performance relative to the ISO35MDWR baseline:

Category A – Equivalent Isolation (2500Vrms–2750Vrms): MAX14945EWE+, MAX14945EWE+T Category B – Enhanced Isolation (5000Vrms): MAX14948EWE+, MAX14948EWE+T, MAX14949EWE+, MAX14949EWE+T, ISO1412DWR

Parameter Comparison

Engineering Selection Recommendations

For Direct Functional Replacement (Preferred):

MAX14948EWE+ and MAX14948EWE+T are the primary substitutes. Both maintain the 3-channel, 2/1 configuration with capacitive coupling isolation technology and ROHS3 compliance. The 5000Vrms isolation rating provides enhanced margin over the 2500Vrms baseline. Data rate is reduced to 500kbps, which is acceptable for most RS422/RS485 applications. Supply voltage range (1.71V–5.5V) encompasses the ISO35MDWR requirement. Operating temperature range (-40°C to 85°C) covers standard industrial conditions but does not extend to the -55°C lower limit of the original part. MSL rating improves to 1 (Unlimited).

MAX14945EWE+ and MAX14945EWE+T offer equivalent isolation voltage (2750Vrms) with identical channel configuration. These are suitable where the lower isolation rating is acceptable and cost optimization is prioritized. Same temperature and MSL considerations apply.

For Applications Requiring Full Duplex Operation:

ISO1412DWR is a full-duplex transceiver with 1/1 channel configuration. This part is functionally distinct from the ISO35MDWR due to different channel topology and is suitable only for applications where full-duplex communication is required and the 2/1 unidirectional configuration is not a design constraint.

Temperature Range Consideration:

If the application requires operation below -40°C, the ISO35MDWR cannot be directly replaced by any listed substitute. Design review is necessary to determine if temperature range relaxation is acceptable.

Packaging and Compliance:

All substitute parts are available in 16-SOIC package format with ROHS3 and REACH compliance matching the original specification. Tape & Reel (TR) packaging is available for MAX14948EWE+T and MAX14945EWE+T, suitable for automated assembly processes.

Frequently Asked Questions (FAQ)

Q: Can MAX14948EWE+ directly replace ISO35MDWR in existing designs?

A: Functional replacement is possible with design verification. The 3-channel, 2/1 configuration, capacitive coupling technology, and 16-SOIC package are identical. Key differences are reduced data rate (500kbps vs. 1Mbps) and narrower operating temperature range (-40°C to 85°C vs. -55°C to 125°C). Verify that your application does not require 1Mbps operation or sub-40°C temperatures.

Q: What is the difference between MAX14948EWE+ and MAX14948EWE+T?

A: Both parts are electrically identical. MAX14948EWE+ is supplied in Tube packaging; MAX14948EWE+T is supplied in Tape & Reel (TR) packaging. Selection depends on assembly process requirements. TR packaging is standard for automated pick-and-place assembly.

Q: Why is ISO1412DWR listed as a substitute if it has only 1 channel?

A: ISO1412DWR is included as a substitute for applications where full-duplex RS422/RS485 communication is required. It is not a direct replacement for the ISO35MDWR due to different channel configuration (1/1 full duplex vs. 2/1 unidirectional). Use only if your application topology supports full-duplex operation.

Q: Does the higher isolation voltage of MAX14948 parts affect compatibility?

A: No. Higher isolation voltage (5000Vrms vs. 2500Vrms) provides additional safety margin and is fully backward compatible. It does not degrade performance in applications designed for 2500Vrms isolation.

Q: Are there supply voltage compatibility issues with the substitutes?

A: MAX14948 and MAX14945 parts support 1.71V–5.5V supply range, which encompasses the ISO35MDWR requirement of 3.15V–3.6V. MAX14949 parts support 3V–5.5V, which also covers the original specification. No supply voltage incompatibility exists.

Q: What is the impact of reduced data rate (500kbps vs. 1Mbps)?

A: The substitute parts operate at 500kbps maximum. If your application requires 1Mbps operation, these substitutes are not suitable. Verify actual data rate requirements in your system design. Many RS422/RS485 industrial applications operate at 115.2kbps to 460.8kbps, making 500kbps sufficient.

Q: Can I use MAX14949EWE+ instead of MAX14948EWE+?

A: Both parts are electrically equivalent with identical isolation voltage (5000Vrms), channel configuration (2/1), and data rate (500kbps). MAX14949 is available in Tube and unspecified packaging; MAX14948 is available in Tube and TR packaging. Selection depends on packaging preference and availability.

Q: What is the MSL rating difference, and does it matter?

A: ISO35MDWR has MSL 2 (1 Year); substitute parts have MSL 1 (Unlimited). MSL rating indicates moisture sensitivity. Lower MSL (1) means the part is less sensitive to moisture and has longer shelf life without special storage. This is an improvement over the original part.

Q: Is there a substitute that maintains the -55°C lower operating temperature limit?

A: No. All listed substitutes have a -40°C lower operating temperature limit. If your application requires -55°C operation, these parts are not suitable. Consult with component suppliers for alternative solutions.