LM285Z-1.2 Shunt Voltage Reference IC Equivalent & Substitute Parts

Part Overview

The LM285Z-1.2 is a shunt voltage reference IC manufactured by onsemi, providing a fixed 1.235V output with ±1% tolerance in a TO-92-3 package. This part is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements. The device operates across the industrial temperature range of -40°C to 85°C and delivers 20 mA output current, suitable for precision voltage reference applications in power management circuits.

Key Parameters

Parameter	Value
Reference Type	Shunt
Output Type	Fixed
Voltage - Output (Min/Fixed)	1.235V
Current - Output	20 mA
Tolerance	±1%
Temperature Coefficient	80ppm/°C Typical
Noise - 10Hz to 10kHz	60µVrms
Current - Cathode	20 µA
Operating Temperature	-40°C ~ 85°C (TA)
Mounting Type	Through Hole
Package / Case	TO-226-3, TO-92-3 Long Body
Supplier Device Package	TO-92 (TO-226)

Substitute Part Grouping Explanation

Substitution for the LM285Z-1.2 is determined by strict alignment of the following electrical and mechanical parameters:

Primary Substitution Criteria:

Reference Type: Shunt
Output Type: Fixed
Voltage - Output: 1.235V
Current - Output: 20 mA
Tolerance: ±1%
Package / Case: TO-226-3 or TO-92-3
Mounting Type: Through Hole

Direct Substitutes maintain all primary criteria with identical electrical performance and package compatibility. These parts are pin-for-pin compatible and require no circuit modifications.

Similar Substitutes meet the primary electrical criteria but may differ in secondary parameters such as temperature coefficient, cathode current, or operating temperature range. These parts are functionally equivalent but may require application-level verification for temperature-sensitive or precision-critical circuits.

Limited Substitutes deviate from standard parameters in output current, tolerance, or operating temperature range. These parts are suitable only for applications where the specific deviation does not impact circuit performance.

Parameter Comparison

Part Number	Manufacturer	Voltage Output	Current Output	Tolerance	Temp Coeff (ppm/°C)	Cathode Current (µA)	Operating Temp (°C)	Package	Product Status	RoHS Status
LM285Z-1.2	onsemi	1.235V	20 mA	±1%	80	20	-40 ~ 85	TO-92-3	Obsolete	Non-compliant
LM285Z-1.2G	onsemi	1.235V	20 mA	±1%	80	20	-40 ~ 85	TO-92-3	Active	ROHS3 Compliant
LM285LP-1-2	Texas Instruments	1.235V	20 mA	±1%	20	10	-40 ~ 85	TO-92-3	Active	ROHS3 Compliant
LM285BXZ-1.2/NOPB	Texas Instruments	1.235V	20 mA	±1%	30	10	-40 ~ 85	TO-92-3	Active	ROHS3 Compliant
LM285LPE3-1-2	Texas Instruments	1.235V	20 mA	±1%	20	10	-40 ~ 85	TO-92-3	Active	ROHS3 Compliant
LM285Z-1.2#PBF	Analog Devices Inc.	1.235V	20 mA	±1%	20	10	-40 ~ 85	TO-92-3	Active	ROHS3 Compliant
LM285Z-1.2/NOPB	Texas Instruments	1.235V	20 mA	±1%	150	10	-40 ~ 85	TO-92-3	Active	ROHS3 Compliant
LM385BLPR-1-2	Texas Instruments	1.235V	20 mA	±1%	20	15	0 ~ 70	TO-92-3	Active	ROHS3 Compliant
LM385BLPRE3-1-2	Texas Instruments	1.235V	20 mA	±1%	20	15	0 ~ 70	TO-92-3	Active	ROHS3 Compliant
LM385BXZ-1.2/NOPB	Texas Instruments	1.235V	20 mA	±1%	30	15	0 ~ 70	TO-92-3	Active	ROHS3 Compliant
AD589SH	Analog Devices Inc.	1.235V	5 mA	-2.83%, +1.22%	100	50	-55 ~ 125	TO-51-2	Active	ROHS3 Compliant

Engineering Selection Recommendations

Direct Substitutes (Pin-for-Pin Compatible, No Circuit Modification Required):

LM285Z-1.2G is the primary direct substitute. It maintains identical electrical specifications and package configuration while offering active product status and ROHS3 compliance, addressing the obsolescence of the original LM285Z-1.2.

Preferred Active Alternatives (Electrical Equivalence with Minor Parameter Variations):

LM285LP-1-2, LM285LPE3-1-2, and LM285Z-1.2#PBF are active alternatives from established manufacturers. These parts deliver the required 1.235V output at 20 mA with ±1% tolerance and full -40°C to 85°C operating range. Lower temperature coefficients (20ppm/°C vs. 80ppm/°C) and reduced cathode current (10µA vs. 20µA) represent performance improvements suitable for precision applications. All three carry ROHS3 compliance.

LM285Z-1.2/NOPB from Texas Instruments provides the highest inventory availability (72,762 units) with identical electrical specifications and full temperature range support. The elevated temperature coefficient (150ppm/°C) is the only secondary parameter deviation.

Temperature-Constrained Alternatives:

LM385BLPR-1-2, LM385BLPRE3-1-2, and LM385BXZ-1.2/NOPB operate within the 0°C to 70°C range, restricting use to commercial and industrial applications excluding the full -40°C lower bound. These parts are suitable for designs not requiring extended low-temperature operation.

Limited Substitutes (Significant Parameter Deviations):

AD589SH from Analog Devices Inc. operates in a different package (TO-51-2 metal can) and delivers only 5 mA output current versus the required 20 mA. Tolerance specification (-2.83%, +1.22%) deviates from ±1%. This part is suitable only for applications where lower output current and asymmetric tolerance are acceptable. The extended operating range (-55°C to 125°C) provides advantage for extreme temperature environments.

Compliance and Availability Considerations:

All recommended active substitutes carry ROHS3 compliance, addressing regulatory requirements for new designs. The original LM285Z-1.2 is RoHS non-compliant and obsolete. Inventory levels vary significantly; LM285Z-1.2/NOPB offers the highest stock position for immediate procurement.

Frequently Asked Questions (FAQ)

Q: Can LM285Z-1.2G be used as a direct replacement for the obsolete LM285Z-1.2?

A: Yes. LM285Z-1.2G is a direct substitute with identical electrical specifications (1.235V, 20 mA, ±1%), package configuration (TO-92-3), and pin assignment. No circuit modifications are required. The primary advantage is active product status and ROHS3 compliance.

Q: What is the difference between LM285 and LM385 series parts?

A: Both series deliver 1.235V fixed output at 20 mA with ±1% tolerance in TO-92-3 packages. The LM385 variants operate within the 0°C to 70°C commercial/industrial range, while LM285 variants support the full -40°C to 85°C industrial range. LM385 parts are suitable for applications not requiring extended low-temperature operation.

Q: Why do some substitutes have lower cathode current (10µA vs. 20µA)?

A: Cathode current represents the minimum operating current required to maintain regulation. Lower cathode current indicates improved efficiency and reduced power dissipation. Parts with 10µA cathode current (LM285LP-1-2, LM285LPE3-1-2, LM285Z-1.2#PBF) are functionally equivalent and represent performance improvements over the original 20µA specification.

Q: Is AD589SH compatible with the LM285Z-1.2 application?

A: AD589SH is not a direct substitute. It delivers only 5 mA output current versus the required 20 mA, uses a different package (TO-51-2 metal can), and carries asymmetric tolerance (-2.83%, +1.22%). Use AD589SH only in applications where lower output current and different tolerance are acceptable.

Q: Which substitute offers the best temperature coefficient performance?

A: LM285LP-1-2, LM285LPE3-1-2, and LM285Z-1.2#PBF all provide 20ppm/°C temperature coefficient, representing significant improvement over the original 80ppm/°C specification. These parts are preferred for temperature-sensitive precision applications.

Q: Are all recommended substitutes ROHS3 compliant?

A: Yes. All active substitute parts listed carry ROHS3 compliance. The original LM285Z-1.2 is RoHS non-compliant. ROHS3 compliance is mandatory for new designs and production in regulated markets.

Q: What is the inventory status for immediate procurement?

A: LM285Z-1.2/NOPB offers the highest availability at 72,762 units. LM285Z-1.2G provides 55,200 units. LM285LP-1-2 and LM385BLPR-1-2 offer moderate availability at 1,841 and 12,100 units respectively. Inventory levels are subject to change; verify current stock with suppliers before final procurement decisions.

Q: Can I use LM285Z-1.2/NOPB in place of LM285Z-1.2G?

A: Yes. Both parts deliver 1.235V at 20 mA with ±1% tolerance and full -40°C to 85°C operation in TO-92-3 packages. The primary difference is temperature coefficient (150ppm/°C vs. 80ppm/°C). LM285Z-1.2/NOPB is suitable for applications where the higher temperature coefficient does not impact performance, and it offers significantly higher inventory availability.

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