LM2937IMP-3.3 Equivalent & Substitute Parts

Part Overview

The LM2937IMP-3.3 is a linear voltage regulator IC from Texas Instruments, delivering a fixed 3.3V output at 500mA in a SOT-223-4 surface mount package. This device is classified as Last Time Buy, indicating discontinued production. The regulator features mirror-image insertion protection, over-temperature shutdown, short-circuit protection, and transient voltage suppression across an operating temperature range of -40°C to 85°C with a maximum input voltage of 26V and 1V dropout at 500mA.

Alternative models are necessary due to the Last Time Buy status, which restricts future availability. Equivalent and substitute parts maintain the same output voltage, package compatibility, and electrical performance characteristics while offering active product status and improved compliance certifications.

Key Parameters

Parameter	Value
Output Voltage (Fixed)	3.3V
Output Current	500mA
Input Voltage (Max)	26V
Voltage Dropout (Max)	1V @ 500mA
Quiescent Current	10 mA
Package Type	SOT-223-4
Operating Temperature	-40°C ~ 85°C
Protection Features	Mirror-Image Insertion, Over Temperature, Short Circuit, Transient Voltage

Substitute Part Grouping Explanation

Substitution of the LM2937IMP-3.3 is determined by the following critical parameters:

Fixed output voltage of 3.3V
Output current capability of 500mA or greater
Maximum input voltage of 26V or higher
Voltage dropout specification of 1V or less at rated current
Surface mount package compatibility (SOT-223 variants)
Operating temperature range encompassing -40°C to 85°C minimum
Protection features including over-temperature and short-circuit protection

Substitute parts are grouped into two categories: parametric equivalents from Texas Instruments with identical electrical specifications, and manufacturer-recommended alternatives from Analog Devices and Microchip Technology that meet or exceed the performance requirements while offering higher output current capability or improved quiescent current characteristics.

Parameter Comparison

Part Number	Manufacturer	Output Current	Input Voltage (Max)	Dropout @ Rated Current	Quiescent Current	Package	Operating Temp	Product Status	RoHS Status
LM2937IMP-3.3	Texas Instruments	500mA	26V	1V @ 500mA	10 mA	SOT-223-4	-40°C ~ 85°C	Last Time Buy	RoHS Non-Compliant
LM2937IMP-3.3/NOPB	Texas Instruments	500mA	26V	1V @ 500mA	10 mA	SOT-223-4	-40°C ~ 85°C	Active	ROHS3 Compliant
LM2937IMPX-3.3/NOPB	Texas Instruments	500mA	26V	1V @ 500mA	10 mA	SOT-223-4	-40°C ~ 85°C	Active	ROHS3 Compliant
LT1121CST-3.3#TRPBF	Analog Devices Inc.	150mA	30V	0.7V @ 150mA	50 µA	SOT-223-3	0°C ~ 125°C	Active	ROHS3 Compliant
LT1129CST-3.3#PBF	Analog Devices Inc.	700mA	30V	0.7V @ 700mA	70 µA	SOT-223-3	0°C ~ 125°C	Active	ROHS3 Compliant
LT1129CST-3.3#TRPBF	Analog Devices Inc.	700mA	30V	0.7V @ 700mA	70 µA	SOT-223-3	0°C ~ 125°C	Active	ROHS3 Compliant
LT1129IST-3.3#PBF	Analog Devices Inc.	700mA	30V	0.7V @ 700mA	70 µA	SOT-223-3	-40°C ~ 125°C	Active	ROHS3 Compliant
LT1129IST-3.3#TRPBF	Analog Devices Inc.	700mA	30V	0.7V @ 700mA	70 µA	SOT-223-3	-40°C ~ 125°C	Active	ROHS3 Compliant
LT1129MPST-3.3#PBF	Analog Devices Inc.	700mA	30V	0.7V @ 700mA	70 µA	SOT-223-3	-55°C ~ 125°C	Active	ROHS3 Compliant
LT1129MPST-3.3#TRPBF	Analog Devices Inc.	700mA	30V	0.7V @ 700mA	70 µA	SOT-223-3	-55°C ~ 125°C	Active	ROHS3 Compliant
MCP1804T-3302I/DB	Microchip Technology	150mA	28V	1.7V @ 100mA	105 µA	SOT-223-3	-40°C ~ 85°C	Active	ROHS3 Compliant

Engineering Selection Recommendations

Primary Equivalents (Texas Instruments LM2937 Series)

LM2937IMP-3.3/NOPB and LM2937IMPX-3.3/NOPB are direct parametric equivalents with identical electrical specifications and SOT-223-4 package compatibility. Both parts are in Active product status with ROHS3 compliance, addressing the Last Time Buy limitation of the original LM2937IMP-3.3. These parts maintain 500mA output current, 1V dropout at rated current, and -40°C to 85°C operating temperature range. Selection between these variants depends on packaging preference (Cut Tape & Digi-Reel vs. alternative packaging).

Higher Current Alternatives (Analog Devices LT1129 Series)

The LT1129 family delivers 700mA output current, exceeding the 500mA requirement of the original part. All LT1129 variants feature 0.7V dropout at 700mA, lower quiescent current (70 µA vs. 10 mA), and 30V maximum input voltage. Temperature range variants include LT1129CST-3.3 (0°C to 125°C), LT1129IST-3.3 (-40°C to 125°C), and LT1129MPST-3.3 (-55°C to 125°C). Package variants include SOT-223-3 in Tube or Tape & Reel configurations. These parts are suitable for applications requiring higher current capacity or extended temperature operation.

Lower Current Alternative (Analog Devices LT1121CST-3.3#TRPBF)

The LT1121CST-3.3#TRPBF provides 150mA output current with 0.7V dropout, lower quiescent current (50 µA), and 30V maximum input voltage. Operating temperature range is 0°C to 125°C. This part is appropriate for current-limited applications where the full 500mA capability is not required.

Temperature-Matched Alternative (Microchip MCP1804T-3302I/DB)

The MCP1804T-3302I/DB maintains the -40°C to 85°C operating temperature range of the original part with 150mA output current. Maximum input voltage is 28V. This part is suitable for applications requiring temperature range compatibility with reduced current requirements.

All substitute parts are ROHS3 compliant and in Active product status, ensuring long-term availability and regulatory compliance.

Frequently Asked Questions (FAQ)

Q: Can LM2937IMP-3.3/NOPB be used as a direct replacement for LM2937IMP-3.3?

A: Yes. LM2937IMP-3.3/NOPB is a parametric equivalent with identical electrical specifications, output voltage, current rating, dropout voltage, and package type. The primary difference is product status (Active vs. Last Time Buy) and RoHS compliance (ROHS3 vs. non-compliant). Pin-for-pin compatibility is maintained.

Q: What is the difference between SOT-223-4 and SOT-223-3 packages?

A: SOT-223-4 contains four pins, while SOT-223-3 contains three pins. The LM2937IMP-3.3 uses SOT-223-4, while most Analog Devices LT1129 variants use SOT-223-3. Physical footprint dimensions differ; PCB layout modifications are required for package migration.

Q: Can LT1129 series parts replace LM2937IMP-3.3 in existing designs?

A: LT1129 parts meet or exceed electrical performance requirements (higher output current, lower dropout, higher input voltage rating). However, package migration from SOT-223-4 to SOT-223-3 requires PCB redesign. Quiescent current is lower (70 µA vs. 10 mA), which may affect circuit behavior in low-power standby conditions. Enable control features present on LT1129 are absent on LM2937.

Q: Which substitute part is recommended for extended temperature operation?

A: LT1129MPST-3.3 variants support -55°C to 125°C operating temperature, the widest range available. LT1129IST-3.3 variants support -40°C to 125°C. Both exceed the original -40°C to 85°C range.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All substitute parts listed are ROHS3 compliant. The original LM2937IMP-3.3 is RoHS non-compliant.

Q: What is the inventory status of substitute parts?

A: LM2937IMP-3.3/NOPB has 39,400 units in stock. LM2937IMPX-3.3/NOPB has 25,200 units. LT1129 variants range from 898 to 4,879 units depending on temperature and packaging options. LT1121CST-3.3#TRPBF has 25,335 units. MCP1804T-3302I/DB has 3,800 units.

Q: Can lower-current alternatives (LT1121, MCP1804) be used if the application requires less than 500mA?

A: Yes, if the application current requirement does not exceed the rated output of the substitute part. LT1121 and MCP1804 are rated at 150mA. Verify actual circuit current draw before selection.

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