DS8921ATM Equivalent & Substitute Parts

Part Overview

The DS8921ATM is a 1/1 transceiver IC with full-duplex RS422 capability in an 8-SOIC surface mount package. This part is classified as obsolete, which necessitates identification of equivalent and substitute components for ongoing design support and procurement. The DS8921ATM operates within a 4.5V to 5.5V supply voltage range and maintains performance across the -40°C to 85°C industrial temperature range with 70 mV receiver hysteresis.

Substiute Parts

DS8921ATM

Texas InstrumentsIn Stock: 1787DS8921ATM Datasheet

Current PartRFQ

DS8921ATM/NOPB

Texas InstrumentsIn Stock: 1489DS8921ATM/NOPB Datasheet

DirectRFQ

SN65HVD485ED

Texas InstrumentsIn Stock: 2093SN65HVD485ED Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the DS8921ATM is determined by the following critical parameters:

Primary Compatibility Criteria:

• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Mounting Type: Surface Mount
• Voltage - Supply: 4.5V ~ 5.5V
• Operating Temperature: -40°C ~ 85°C
• Protocol Support: RS422 minimum

Secondary Compatibility Criteria:

• Number of Drivers/Receivers: 1/1
• Duplex Mode: Full (preferred for direct replacement)
• Receiver Hysteresis: 70 mV (preferred for signal integrity equivalence)

Substitute parts are grouped into two categories:

Category 1 - Direct Functional Equivalent: DS8921ATM/NOPB maintains identical electrical specifications and duplex characteristics, differing only in packaging format (Tube vs. unspecified) and product status (Active vs. Obsolete).

Category 2 - Functional Substitute with Parameter Variance: SN65HVD485ED provides RS422/RS485 protocol support and identical package/voltage/temperature specifications but operates in half-duplex mode with reduced receiver hysteresis (30 mV) and specified data rate capability (10 Mbps).

Parameter Comparison

Engineering Selection Recommendations

DS8921ATM/NOPB is the preferred substitute for direct replacement applications. This part maintains full electrical and functional equivalence to the DS8921ATM while offering Active product status and ROHS3 compliance. The transition from unspecified packaging to Tube packaging does not affect electrical performance or PCB integration. This option is suitable for designs requiring full-duplex RS422 operation with 70 mV receiver hysteresis.

SN65HVD485ED is applicable for applications where half-duplex operation is acceptable and where the reduced receiver hysteresis (30 mV) does not compromise signal integrity requirements. This part offers ROHS3 compliance and specified 10 Mbps data rate capability. However, the transition from full-duplex to half-duplex mode requires circuit topology verification. The Last Time Buy status indicates limited future availability.

For new designs, DS8921ATM/NOPB is the recommended path forward due to Active product status and functional equivalence. For legacy system maintenance where full-duplex operation is non-negotiable, DS8921ATM/NOPB provides the most direct continuity.

Frequently Asked Questions (FAQ)

Q: Can DS8921ATM/NOPB be used as a direct replacement for DS8921ATM?

A: Yes. DS8921ATM/NOPB is electrically and functionally identical to DS8921ATM. Both parts share identical protocol (RS422), duplex mode (Full), receiver hysteresis (70 mV), supply voltage (4.5V ~ 5.5V), operating temperature range (-40°C ~ 85°C), and package (8-SOIC). The only difference is packaging format (Tube) and product status (Active vs. Obsolete). Pin-for-pin compatibility is maintained.

Q: What are the key differences between DS8921ATM and SN65HVD485ED?

A: The primary difference is duplex mode: DS8921ATM operates in full-duplex, while SN65HVD485ED operates in half-duplex. Additionally, SN65HVD485ED has reduced receiver hysteresis (30 mV vs. 70 mV) and specifies a 10 Mbps data rate. Both share identical package, supply voltage, and operating temperature specifications. Half-duplex operation requires unidirectional communication or time-division multiplexing, which may not be compatible with full-duplex circuit designs.

Q: Are there package compatibility concerns with these substitutes?

A: No. All three parts (DS8921ATM, DS8921ATM/NOPB, and SN65HVD485ED) use the 8-SOIC (0.154", 3.90mm Width) surface mount package. PCB footprints and reflow soldering processes are identical across all three parts.

Q: What is the significance of product status (Obsolete, Active, Last Time Buy)?

A: Product status indicates lifecycle stage. Obsolete parts have reached end-of-life and are no longer manufactured; existing inventory is finite. Active parts are in current production with ongoing availability. Last Time Buy indicates the manufacturer has announced final production, after which the part becomes obsolete. For procurement planning, Active status (DS8921ATM/NOPB) provides the longest supply continuity.

Q: Can SN65HVD485ED be used in a full-duplex RS422 application?

A: SN65HVD485ED is rated for half-duplex operation only. Using it in a full-duplex application would require circuit redesign to accommodate half-duplex communication protocols. The electrical specifications do not support simultaneous bidirectional transmission.

Q: Are there compliance differences between these parts?

A: Yes. DS8921ATM is RoHS non-compliant. Both DS8921ATM/NOPB and SN65HVD485ED are ROHS3 compliant. All three parts are REACH Unaffected and classified as EAR99 for export control purposes. For applications requiring RoHS compliance, DS8921ATM/NOPB or SN65HVD485ED must be selected.