MIC2937A-3.3BT Linear Voltage Regulator Equivalent & Substitute Parts

Part Overview

The MIC2937A-3.3BT is a linear voltage regulator IC from Microchip Technology designed to deliver a fixed 3.3V output at 750mA in a TO-220-3 package. This part is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements. The device provides positive fixed output regulation with integrated over-current and over-temperature protection, suitable for applications requiring stable 3.3V power delivery from input sources up to 26V.

Key Parameters

Parameter	Value
Output Voltage (Fixed)	3.3V
Output Current	750mA
Input Voltage (Max)	26V
Quiescent Current	300 µA
Operating Temperature Range	-40°C to 125°C
Package Type	TO-220-3
Protection Features	Over Current, Over Temperature
Mounting Type	Through Hole

Substitute Part Grouping Explanation

Substitution for the MIC2937A-3.3BT is determined by the following critical parameters:

Output Voltage: Must be fixed at 3.3V
Package Type: Must be TO-220-3 for mechanical and thermal compatibility
Mounting Type: Must be through-hole
Output Configuration: Must be positive fixed output
Operating Temperature Range: Must support -40°C to 125°C or equivalent
Protection Features: Must include over-current and over-temperature protection

Substitute parts are grouped into two categories:

Direct Equivalent: Identical electrical specifications and output current rating (750mA)
Functional Alternatives: Same output voltage and package, with different output current ratings or input voltage specifications that remain compatible with the application

Parameter Comparison

Part Number	Manufacturer	Output Voltage	Output Current	Input Voltage (Max)	Quiescent Current	Operating Temp Range	Package	Product Status	RoHS Status
MIC2937A-3.3BT	Microchip Technology	3.3V	750mA	26V	300 µA	-40°C to 125°C	TO-220-3	Obsolete	Non-compliant
MIC2937A-3.3WT	Microchip Technology	3.3V	750mA	26V	300 µA	-40°C to 125°C	TO-220-3	Active	ROHS3 Compliant
TC1264-3.3VAB	Microchip Technology	3.3V	800mA	6V	130 µA	-40°C to 125°C	TO-220-3	Active	ROHS3 Compliant
LM2937ET-3.3/NOPB	Texas Instruments	3.3V	500mA	26V	10 mA	-40°C to 125°C	TO-220-3	Active	ROHS3 Compliant
LM3940IT-3.3/NOPB	Texas Instruments	3.3V	1A	7.5V	Not specified	-40°C to 125°C	TO-220-3	Active	ROHS3 Compliant
LT1086CT-3.3#PBF	Analog Devices Inc.	3.3V	1.5A	20V	10 mA	0°C to 125°C	TO-220-3	Active	ROHS3 Compliant
LT1086IT-3.3#PBF	Analog Devices Inc.	3.3V	1.5A	20V	10 mA	-40°C to 125°C	TO-220-3	Active	ROHS3 Compliant

Engineering Selection Recommendations

Primary Recommendation: MIC2937A-3.3WT

The MIC2937A-3.3WT is the direct equivalent to the obsolete MIC2937A-3.3BT. It maintains identical electrical specifications (3.3V output, 750mA current, 26V maximum input) and identical TO-220-3 packaging. The primary distinction is product status and compliance: MIC2937A-3.3WT is active and ROHS3 compliant, whereas the original part is obsolete and non-compliant. This part is the preferred choice for direct replacement in existing designs.

Secondary Recommendations Based on Application Requirements:

LT1086IT-3.3#PBF: Select when higher output current (1.5A) is required and the application can tolerate the full -40°C to 125°C operating range. This part offers superior current capability and PSRR performance (72dB at 120Hz).
LM3940IT-3.3/NOPB: Select when output current requirement is 1A or less and input voltage is limited to 7.5V or below. This part offers the lowest dropout voltage (0.2V @ 100mA).
TC1264-3.3VAB: Select when input voltage is constrained to 6V or below and output current of 800mA is sufficient. This part offers the lowest quiescent current (130 µA).
LM2937ET-3.3/NOPB: Select when 500mA output current is sufficient and 26V input voltage compatibility is required. This part maintains the same maximum input voltage as the original.

All substitute parts are active products with ROHS3 compliance, ensuring long-term availability and regulatory compliance for new designs.

Frequently Asked Questions (FAQ)

Q: Can MIC2937A-3.3WT be used as a direct drop-in replacement for MIC2937A-3.3BT?

A: Yes. MIC2937A-3.3WT is electrically and mechanically identical to MIC2937A-3.3BT. The only differences are product status (active vs. obsolete) and RoHS compliance (ROHS3 vs. non-compliant). No circuit modifications are required.

Q: What is the key difference between the Microchip and Texas Instruments substitutes?

A: Microchip parts (MIC2937A-3.3WT, TC1264-3.3VAB) maintain the same manufacturer lineage as the original. Texas Instruments parts (LM2937ET-3.3/NOPB, LM3940IT-3.3/NOPB) offer alternative sourcing with different output current and input voltage specifications. All maintain 3.3V fixed output and TO-220-3 packaging.

Q: Can I use LT1086IT-3.3#PBF if my application only requires 750mA?

A: Yes. The LT1086IT-3.3#PBF is rated for 1.5A output current, making it suitable for applications requiring 750mA or less. The higher current rating provides design margin and does not negatively impact performance at lower current levels.

Q: What is the impact of different input voltage ratings on substitution?

A: Input voltage ratings determine the maximum voltage that can be safely applied to the regulator. The original MIC2937A-3.3BT accepts up to 26V input. Substitutes with lower input voltage ratings (TC1264-3.3VAB at 6V, LM3940IT-3.3/NOPB at 7.5V) are suitable only if your application's input voltage does not exceed these limits. Parts with 20V or 26V ratings maintain full compatibility with the original specification.

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

A: Yes. All substitute parts listed are available in TO-220-3 through-hole packaging, ensuring mechanical and thermal compatibility with the original MIC2937A-3.3BT footprint.

Q: What is the significance of quiescent current differences?

A: Quiescent current (Iq) represents the regulator's internal current consumption when no load is present. Lower Iq values (TC1264-3.3VAB at 130 µA, LT1086 series at 10 mA) reduce standby power consumption. The original MIC2937A-3.3BT has 300 µA Iq. Selection depends on whether standby power efficiency is a design priority.

Q: Can I substitute parts with different operating temperature ranges?

A: The original MIC2937A-3.3BT operates from -40°C to 125°C. LT1086CT-3.3#PBF operates from 0°C to 125°C, which is narrower. Substitution is acceptable only if your application's operating environment does not require temperatures below 0°C. LT1086IT-3.3#PBF maintains the full -40°C to 125°C range and is preferred for wide-temperature applications.

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