SPX385AS-L-1-2 Equivalent & Substitute Parts

Part Overview

The SPX385AS-L-1-2 is a shunt voltage reference IC manufactured by MaxLinear, Inc., designed for precision power management applications. This fixed 1.235V reference device delivers 20 mA output current with ±1% tolerance and operates across the -40°C to 85°C temperature range in an 8-SOIC surface mount package. The part is discontinued at DiGi Electronics, necessitating identification of functionally equivalent alternatives from active product lines to maintain design continuity and ensure long-term supply availability.

Key Parameters

Parameter	SPX385AS-L-1-2
Reference Type	Shunt
Output Type	Fixed
Voltage - Output (Min/Fixed)	1.235V
Current - Output	20 mA
Tolerance	±1%
Temperature Coefficient	50ppm/°C
Noise - 10Hz to 10kHz	60µVrms
Current - Cathode	10 µA
Operating Temperature	-40°C ~ 85°C (TA)
Package / Case	8-SOIC (0.154", 3.90mm Width)
Mounting Type	Surface Mount
RoHS Status	RoHS Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution eligibility for the SPX385AS-L-1-2 is determined by strict equivalence across the following critical parameters:

Reference Type: Shunt (fixed requirement)
Output Voltage: 1.235V (fixed requirement)
Output Current: 20 mA (fixed requirement)
Tolerance: ±1% (fixed requirement)
Package: 8-SOIC with 0.154" width, 3.90mm (fixed requirement)
Operating Temperature Range: -40°C to 85°C (fixed requirement)
Noise Performance: 60µVrms at 10Hz to 10kHz (fixed requirement)
Cathode Current: 10 µA (fixed requirement)

Temperature coefficient, product status, and packaging format (tube, tape & reel, bulk) are secondary parameters that do not prevent substitution but may influence selection based on application requirements and supply chain considerations.

Parameter Comparison

Part Number	Manufacturer	Output Voltage	Output Current	Tolerance	Temp Coeff	Cathode Current	Package	Product Status	Packaging Format
SPX385AS-L-1-2	MaxLinear, Inc.	1.235V	20 mA	±1%	50ppm/°C	10 µA	8-SOIC	Discontinued	-
LM285BXM-1.2/NOPB	National Semiconductor	1.235V	20 mA	±1%	30ppm/°C	10 µA	8-SOIC	Active	Bulk
LM285BXMX-1.2/NOPB	Texas Instruments	1.235V	20 mA	±1%	30ppm/°C	10 µA	8-SOIC	Active	Tape & Reel
LM285BYMX-1.2/NOPB	Texas Instruments	1.235V	20 mA	±1%	50ppm/°C	10 µA	8-SOIC	Active	Tape & Reel
LM285D-1-2	Texas Instruments	1.235V	20 mA	±1%	20ppm/°C	10 µA	8-SOIC	Last Time Buy	Tube
LM285D-1.2G	onsemi	1.235V	20 mA	±1%	80ppm/°C	20 µA	8-SOIC	Active	Tube
LM285D-1.2R2G	onsemi	1.235V	20 mA	±1%	80ppm/°C	20 µA	8-SOIC	Active	Tape & Reel
LM285DG4-1-2	Texas Instruments	1.235V	20 mA	±1%	20ppm/°C	10 µA	8-SOIC	Obsolete	Tube
LM285DR-1-2	Texas Instruments	1.235V	20 mA	±1%	20ppm/°C	10 µA	8-SOIC	Last Time Buy	Cut Tape & Digi-Reel
LM285DRE4-1-2	Texas Instruments	1.235V	20 mA	±1%	20ppm/°C	10 µA	8-SOIC	Obsolete	Tape & Reel
LM285M-1.2/NOPB	Texas Instruments	1.235V	20 mA	±1%	150ppm/°C	10 µA	8-SOIC	Active	Tube

Engineering Selection Recommendations

All listed substitute parts meet the core electrical and mechanical requirements for direct replacement of the SPX385AS-L-1-2. Selection should prioritize parts with Active product status to ensure long-term availability and supply chain stability.

Recommended Primary Substitutes (Active Status):

LM285BXMX-1.2/NOPB (Texas Instruments, Tape & Reel): Active status with superior temperature coefficient (30ppm/°C). ROHS3 compliant. Highest inventory availability (3600 pcs).
LM285BYMX-1.2/NOPB (Texas Instruments, Tape & Reel): Active status with temperature coefficient matching the original part (50ppm/°C). ROHS3 compliant. Largest inventory (5200 pcs).
LM285D-1.2R2G (onsemi, Tape & Reel): Active status with highest inventory (21068 pcs). ROHS3 compliant. Cathode current specification differs (20 µA vs. 10 µA); verify application tolerance before selection.
LM285M-1.2/NOPB (Texas Instruments, Tube): Active status. Higher temperature coefficient (150ppm/°C) requires thermal performance evaluation in temperature-sensitive applications.

Secondary Substitutes (Last Time Buy / Obsolete Status):

Parts with Last Time Buy or Obsolete status should be selected only when Active alternatives are unavailable. These include LM285D-1-2, LM285DR-1-2, LM285DG4-1-2, and LM285DRE4-1-2.

All substitute parts carry RoHS3 compliance and MSL 1 (Unlimited) moisture sensitivity ratings, ensuring compatibility with standard manufacturing and storage protocols.

Frequently Asked Questions (FAQ)

Q: Can LM285D-1.2G or LM285D-1.2R2G be used as direct replacements despite the 20 µA cathode current specification?

A: These onsemi parts meet all primary electrical parameters (1.235V output, 20 mA current, ±1% tolerance, 8-SOIC package). The cathode current difference (20 µA vs. 10 µA) is a secondary parameter. Substitution is valid if the application circuit design accommodates the higher cathode current draw. Verify bias network calculations and power dissipation in the reference circuit.

Q: What is the significance of temperature coefficient differences among substitute parts?

A: Temperature coefficient affects output voltage stability across the -40°C to 85°C operating range. The original SPX385AS-L-1-2 specifies 50ppm/°C. Substitutes range from 20ppm/°C (superior stability) to 150ppm/°C (reduced stability). For applications requiring tight voltage regulation across temperature extremes, select parts with lower temperature coefficients (LM285BXMX-1.2/NOPB at 30ppm/°C or LM285D-1-2 at 20ppm/°C).

Q: Are packaging format differences (Tube, Tape & Reel, Bulk) electrically significant?

A: No. Packaging format affects only supply chain logistics, handling, and assembly processes. Electrical performance is identical. Select based on manufacturing requirements: Tape & Reel for automated assembly, Tube for manual handling, Bulk for high-volume procurement.

Q: Why should Last Time Buy and Obsolete parts be avoided?

A: Last Time Buy status indicates the manufacturer will cease production after current inventory depletes. Obsolete status confirms production has ended. These parts present supply chain risk for long-term product support. Active status parts ensure continued availability for design revisions, field repairs, and production scaling.

Q: Is the LM285BXM-1.2/NOPB (National Semiconductor) a viable substitute?

A: Yes. This part meets all core electrical specifications and carries Active product status. However, inventory availability (1495 pcs) is lower than Texas Instruments and onsemi alternatives. Consider this option if preferred supplier relationships or specific compliance certifications require National Semiconductor sourcing.

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