DS8921AM Equivalent & Substitute Parts

Part Overview

The DS8921AM is a 1/1 transceiver IC for RS422 and RS485 communication protocols, manufactured by Texas Instruments in an 8-SOIC surface mount package. This part is classified as obsolete, which necessitates identification of active equivalent alternatives for new designs and ongoing production requirements. The DS8921AM operates within a 4.5V to 5.5V supply range with full-duplex capability and 70 mV receiver hysteresis, making it suitable for industrial serial communication applications.

Key Parameters

Parameter	Value
Manufacturer Part Number	DS8921AM
Manufacturer	Texas Instruments
Type	Transceiver
Protocol	RS422, RS485
Number of Drivers/Receivers	1/1
Duplex	Full
Receiver Hysteresis	70 mV
Voltage - Supply	4.5V ~ 5.5V
Operating Temperature	0°C ~ 70°C
Package / Case	8-SOIC (0.154", 3.90mm Width)
Mounting Type	Surface Mount
Product Status	Obsolete
RoHS Status	RoHS non-compliant

Substitute Part Grouping Explanation

Substitution of the DS8921AM is determined by strict equivalence across the following parameters: RS422/RS485 protocol support, 1/1 driver/receiver configuration, full-duplex operation, 8-SOIC package format, surface mount technology, and compatible supply voltage ranges. The receiver hysteresis specification (70 mV) and operating temperature range (0°C ~ 70°C) are critical electrical parameters for functional compatibility.

Substitute parts are grouped into two categories:

Direct Equivalents (Identical Electrical Parameters): Parts maintaining the exact receiver hysteresis of 70 mV and supply voltage range of 4.5V ~ 5.5V.

Functional Equivalents (Compatible Electrical Parameters): Parts with minor variations in receiver hysteresis (50 mV) or supply voltage range (4.75V ~ 5.25V) that remain functionally compatible within typical application requirements.

Parameter Comparison

Part Number	Manufacturer	Protocol	Drivers/Receivers	Receiver Hysteresis	Supply Voltage	Operating Temp	Package	Product Status	RoHS Status
DS8921AM	Texas Instruments	RS422, RS485	1/1	70 mV	4.5V ~ 5.5V	0°C ~ 70°C	8-SOIC	Obsolete	RoHS non-compliant
DS8921AM/NOPB	Texas Instruments	RS422, RS485	1/1	70 mV	4.5V ~ 5.5V	0°C ~ 70°C	8-SOIC	Active	ROHS3 Compliant
DS8921M/NOPB	Texas Instruments	RS422, RS485	1/1	70 mV	4.5V ~ 5.5V	0°C ~ 70°C	8-SOIC	Active	ROHS3 Compliant
SN75179BDR	Texas Instruments	RS422, RS485	1/1	50 mV	4.75V ~ 5.25V	0°C ~ 70°C	8-SOIC	Active	ROHS3 Compliant
SN75179BD	Texas Instruments	RS422, RS485	1/1	50 mV	4.75V ~ 5.25V	0°C ~ 70°C	8-SOIC	Obsolete	ROHS3 Compliant
MAX488CSA+	Analog Devices Inc./Maxim Integrated	RS422, RS485	1/1	70 mV	4.75V ~ 5.25V	0°C ~ 70°C	8-SOIC	Active	ROHS3 Compliant

Engineering Selection Recommendations

For new designs and production applications, DS8921AM/NOPB or DS8921M/NOPB are the primary recommended substitutes. Both parts maintain identical electrical parameters to the original DS8921AM while offering active product status and ROHS3 compliance, eliminating obsolescence risk and regulatory concerns.

SN75179BDR represents an active alternative from Texas Instruments with ROHS3 compliance. This part operates within a narrower supply voltage range (4.75V ~ 5.25V) and features reduced receiver hysteresis (50 mV). These variations remain compatible with standard RS422/RS485 applications but require verification that the tighter voltage tolerance and lower hysteresis threshold align with specific circuit requirements.

MAX488CSA+ from Analog Devices Inc./Maxim Integrated is an active cross-manufacturer equivalent with ROHS3 compliance. It maintains the 70 mV receiver hysteresis specification but operates within the 4.75V ~ 5.25V supply range. This part is suitable for applications where cross-manufacturer sourcing is acceptable and supply voltage constraints are not limiting factors.

SN75179BD is obsolete and should not be selected for new designs despite ROHS3 compliance.

Frequently Asked Questions (FAQ)

Q: Can DS8921AM/NOPB directly replace DS8921AM in existing designs?

A: Yes. DS8921AM/NOPB maintains identical electrical specifications including receiver hysteresis (70 mV), supply voltage range (4.5V ~ 5.5V), and package format (8-SOIC). The primary difference is product status (active vs. obsolete) and RoHS compliance (ROHS3 vs. non-compliant).

Q: What is the difference between DS8921AM/NOPB and DS8921M/NOPB?

A: Both parts are parametrically equivalent with identical electrical specifications. The difference lies in the temperature grade designation within the part number. Both are active products with ROHS3 compliance and suitable for direct substitution.

Q: Can SN75179BDR replace DS8921AM in all applications?

A: SN75179BDR is functionally compatible for RS422/RS485 communication but operates within a narrower supply voltage range (4.75V ~ 5.25V vs. 4.5V ~ 5.5V) and features lower receiver hysteresis (50 mV vs. 70 mV). Verify that your circuit design accommodates these parameter variations before substitution.

Q: Is MAX488CSA+ suitable for industrial applications requiring the DS8921AM?

A: MAX488CSA+ is an active cross-manufacturer equivalent with ROHS3 compliance and maintains the 70 mV receiver hysteresis specification. It is suitable for RS422/RS485 applications where the 4.75V ~ 5.25V supply voltage range is compatible with your power supply design.

Q: Why is RoHS compliance important for DS8921AM substitution?

A: RoHS3 compliance ensures the substitute part meets current environmental and regulatory standards for electronic components. The original DS8921AM is RoHS non-compliant, making active, compliant alternatives necessary for new production and designs subject to regulatory requirements.

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

A: All substitute parts listed are available in 8-SOIC surface mount packages with identical physical dimensions (0.154", 3.90mm Width), ensuring mechanical compatibility with existing PCB layouts and assembly processes.

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