FT531IA Linear Voltage Regulator 3V 250mA Equivalent & Substitute Parts

Part Overview

The FT531IA is a linear voltage regulator IC manufactured by Fremont Micro Devices Ltd, designed for positive fixed 3V output at 250mA in a SOT-23-5 surface mount package. This device is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity. The FT531IA operates across -40°C to 85°C with integrated over-current protection and enable control features, suitable for low-power applications requiring stable 3V regulation from input sources up to 6V.

Key Parameters

Parameter	FT531IA
Manufacturer	Fremont Micro Devices Ltd
Output Voltage (Fixed)	3V
Output Current	250mA
Input Voltage (Max)	6V
Voltage Dropout (Max)	0.12V @ 100mA
Quiescent Current	36 µA
Package	SOT-23-5 (SC-74A)
Control Features	Enable
Protection Features	Over Current
Operating Temperature	-40°C ~ 85°C
Product Status	Obsolete
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution for the FT531IA is determined by the following critical parameters: fixed 3V output voltage, minimum 250mA output current capability, maximum 6V input voltage rating, SOT-23-5 or compatible package footprint, surface mount technology, and operating temperature range of -40°C to 85°C or wider. Substitute parts are grouped into two categories:

Direct Parametric Equivalents maintain identical or superior electrical specifications with the same package type, enabling direct replacement without circuit modification.

Similar Functional Alternatives provide 3V fixed output with comparable or higher current ratings in compatible packages, with minor variations in dropout voltage, quiescent current, or temperature range that do not compromise circuit functionality.

The following parameters determine substitution validity:

Output voltage: 3V fixed
Output current: minimum 250mA
Input voltage maximum: 6V or higher
Package: SOT-23-5, SOT-25, or equivalent SC-74A footprint
Surface mount configuration
Operating temperature: -40°C minimum to 85°C minimum

Parameter Comparison

Part Number	Manufacturer	Output Current	Voltage Dropout (Max)	Quiescent Current	Package	Operating Temp	Product Status
FT531IA	Fremont Micro Devices Ltd	250mA	0.12V @ 100mA	36 µA	SOT-23-5	-40°C ~ 85°C	Obsolete
AP2139AK-3.0TRG1	Diodes Incorporated	250mA	0.7V @ 250mA	1.5 µA	SOT-23-5	-40°C ~ 85°C	Active
NCP163ASN300T1G	onsemi	250mA	0.155V @ 250mA	20 µA	SOT-23-5	-40°C ~ 125°C	Active
NCP603SN300T1G	Fairchild Semiconductor	300mA	0.23V @ 300mA	180 µA	SOT-23-5	-40°C ~ 125°C	Active
LDS3985M30R	STMicroelectronics	300mA	0.25V @ 300mA	150 µA	SOT-23-5	-40°C ~ 125°C	Active
AP7335-30WG-7	Diodes Incorporated	300mA	0.2V @ 300mA	80 µA	SOT-25	-40°C ~ 85°C	Active
AP7331-30WG-7	Diodes Incorporated	300mA	0.55V @ 300mA	75 µA	SOT-25	-40°C ~ 85°C	Active
S-1132B30-M5T1U	ABLIC Inc.	300mA	0.19V @ 100mA	1 µA	SOT-23-5	-40°C ~ 85°C	Active
XC6221A302MR-G	Torex Semiconductor Ltd	200mA	0.14V @ 100mA	50 µA	SOT-25	-40°C ~ 85°C	Active
XC6221B302MR-G	Torex Semiconductor Ltd	200mA	0.14V @ 100mA	50 µA	SOT-25	-40°C ~ 85°C	Active

Engineering Selection Recommendations

Primary Substitutes (Direct Replacement)

NCP163ASN300T1G (onsemi) and LDS3985M30R (STMicroelectronics) are the preferred substitutes. Both maintain SOT-23-5 package compatibility, support 250mA or higher output current, and are classified as active products with ROHS3 compliance. NCP163ASN300T1G offers superior dropout voltage performance (0.155V @ 250mA) and extended operating temperature range (-40°C to 125°C). LDS3985M30R provides 300mA output capacity with comparable dropout characteristics and wider temperature support.

Secondary Substitutes (Compatible with Minor Considerations)

AP2139AK-3.0TRG1 (Diodes Incorporated) matches the exact 250mA output current and SOT-23-5 package but exhibits higher dropout voltage (0.7V @ 250mA). This part is suitable for applications where dropout voltage is not a critical constraint.

NCP603SN300T1G (Fairchild Semiconductor) and AP7335-30WG-7 (Diodes Incorporated) provide 300mA output current with low dropout voltage. NCP603SN300T1G maintains SOT-23-5 compatibility, while AP7335-30WG-7 uses SOT-25 package, requiring PCB layout verification for footprint compatibility.

Alternative Substitutes (Current Derating Required)

XC6221A302MR-G and XC6221B302MR-G (Torex Semiconductor Ltd) are suitable only for applications requiring maximum 200mA output current. These parts offer excellent dropout voltage (0.14V @ 100mA) and are ROHS3 compliant but do not meet the 250mA minimum requirement of the original FT531IA specification.

All recommended substitutes are ROHS3 compliant and carry REACH unaffected or compliant status, meeting current regulatory requirements.

Frequently Asked Questions (FAQ)

Q: Can I use a substitute part with higher output current rating than the FT531IA?

A: Yes. Parts rated for 300mA output current (such as NCP603SN300T1G, LDS3985M30R, AP7335-30WG-7, and S-1132B30-M5T1U) are fully compatible with circuits designed for 250mA operation. Higher current rating provides design margin and does not affect circuit functionality.

Q: What is the significance of dropout voltage in selecting a substitute?

A: Dropout voltage determines the minimum input-to-output voltage differential required for proper regulation. Lower dropout voltage (such as 0.12V in FT531IA or 0.155V in NCP163ASN300T1G) allows operation with lower input voltages. Higher dropout voltage (such as 0.7V in AP2139AK-3.0TRG1) requires greater input voltage headroom. Verify your circuit's input voltage range against the substitute's dropout specification.

Q: Are SOT-25 and SOT-23-5 packages interchangeable?

A: SOT-25 and SOT-23-5 packages have different pin configurations and PCB footprints. While both are 5-pin surface mount packages, direct substitution requires PCB layout modification. Verify pinout compatibility and footprint dimensions before selecting parts with different package designations.

Q: What is the impact of quiescent current differences between parts?

A: Quiescent current (Iq) represents the regulator's internal current consumption when supplying no load current. Lower quiescent current (such as 1.5 µA in AP2139AK-3.0TRG1 or 1 µA in S-1132B30-M5T1U) reduces standby power consumption in battery-powered applications. Higher quiescent current (such as 180 µA in NCP603SN300T1G) has minimal impact in applications with continuous load current.

Q: Can I substitute the FT531IA with a part rated for lower maximum input voltage?

A: No. The FT531IA accepts input voltages up to 6V. Substitute parts must maintain this 6V maximum input rating or higher. NCP163ASN300T1G is rated for 5.5V maximum input, which is lower than the original specification and may not be suitable if your circuit supplies 6V input.

Q: Are all listed substitutes ROHS3 compliant?

A: Yes. All substitute parts listed in this document are ROHS3 compliant, meeting current environmental and regulatory requirements for electronic components.

Request Quote (Ships tomorrow)

Part Number

Quantity

Company

Contact Name

E-mail

Message