FT531JA Linear Voltage Regulator IC Equivalent & Substitute Parts

Part Overview

The FT531JA is a linear voltage regulator IC manufactured by Fremont Micro Devices Ltd, designed to deliver a fixed 3.3V output at 250mA in a surface-mount SOT-23-5 package. This device is classified as obsolete, making equivalent and substitute parts necessary for new designs and production continuity. The FT531JA serves applications requiring low-dropout regulation with enable control and overcurrent protection in compact form factors.

Key Parameters

Parameter	FT531JA
Output Voltage (Fixed)	3.3V
Output Current	250mA
Input Voltage (Max)	6V
Dropout Voltage (Max)	0.12V @ 100mA
Quiescent Current	36 µA
PSRR	72dB ~ 60dB (1kHz ~ 10kHz)
Operating Temperature	-40°C ~ 85°C
Package	SOT-23-5 (SC-74A)
Control Features	Enable
Protection Features	Over Current

Substitute Part Grouping Explanation

Substitute parts for the FT531JA are selected based on strict electrical and mechanical compatibility criteria. The primary substitution parameters are:

Fixed output voltage of 3.3V
Output current capability of 250mA or greater
Maximum input voltage of 6V or higher
SOT-23-5 package compatibility
Enable control feature
Overcurrent protection

Substitute parts are grouped into two categories:

Direct Electrical Equivalents: Parts meeting all primary electrical specifications with identical or superior performance characteristics and active product status.

Parametric Equivalents: Parts meeting core electrical requirements with acceptable variations in secondary parameters such as quiescent current, dropout voltage, or PSRR, suitable for applications where the FT531JA specifications are not critical.

Parameter Comparison

Parameter	FT531JA	LP5907MFX-3.3/NOPB	NCP163ASN330T1G	REG102NA-3.3/3K	S-1132B33-M5T1U	XC6219A332MR-G	AP2139AK-3.3TRG1
Manufacturer	Fremont Micro Devices Ltd	Texas Instruments	onsemi	Texas Instruments	ABLIC Inc.	Torex Semiconductor Ltd	Diodes Incorporated
Output Voltage	3.3V	3.3V	3.3V	3.3V	3.3V	3.3V	3.3V
Output Current	250mA	250mA	250mA	250mA	300mA	240mA	250mA
Input Voltage (Max)	6V	5.5V	5.5V	10V	6.5V	6V	6V
Dropout Voltage (Max)	0.12V @ 100mA	0.25V @ 250mA	0.145V @ 250mA	0.27V @ 250mA	0.15V @ 100mA	0.25V @ 100mA	0.6V @ 250mA
Quiescent Current	36 µA	25 µA	20 µA	500 µA	1 µA	55 µA	1.5 µA
PSRR	72dB ~ 60dB (1kHz ~ 10kHz)	90dB ~ 60dB (100Hz ~ 100kHz)	91dB ~ 60dB (100Hz ~ 100kHz)	65dB (120Hz)	65dB (1kHz)	70dB (10kHz)	Not specified
Operating Temperature	-40°C ~ 85°C	-40°C ~ 125°C	-40°C ~ 125°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Package	SOT-23-5	SOT-23-5	SOT-23-5	SOT-23-5	SOT-23-5	SOT-25-5	SOT-23-5
Product Status	Obsolete	Active	Active	Last Time Buy	Active	Active	Active
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Recommended Primary Substitutes:

LP5907MFX-3.3/NOPB (Texas Instruments) and NCP163ASN330T1G (onsemi) are the preferred substitutes for the FT531JA. Both devices are in active production status, ROHS3 compliant, and deliver superior electrical performance. The LP5907MFX-3.3/NOPB offers improved PSRR (90dB ~ 60dB) and lower quiescent current (25 µA), while the NCP163ASN330T1G provides the lowest quiescent current (20 µA) and enhanced protection features including soft start. Both support the full 250mA output current requirement and operate within the -40°C ~ 125°C temperature range, exceeding the FT531JA specification.

Secondary Substitutes:

S-1132B33-M5T1U (ABLIC Inc.) is suitable for applications prioritizing ultra-low quiescent current (1 µA) and is actively produced with ROHS3 compliance. This device supports 300mA output current, providing additional design margin. XC6219A332MR-G (Torex Semiconductor Ltd) is an active alternative with comparable dropout voltage and PSRR characteristics, though output current is rated at 240mA.

Conditional Substitute:

REG102NA-3.3/3K (Texas Instruments) carries Last Time Buy status and exhibits higher quiescent current (500 µA), making it suitable only for applications where power consumption is not critical. This device supports higher input voltage (10V maximum) and is ROHS3 compliant.

Limited Substitute:

AP2139AK-3.3TRG1 (Diodes Incorporated) meets core electrical requirements but exhibits significantly higher dropout voltage (0.6V @ 250mA) and carries MSL-3 moisture sensitivity rating. This device is suitable only for applications with relaxed dropout voltage requirements and appropriate moisture handling procedures.

Frequently Asked Questions (FAQ)

Q: Can LP5907MFX-3.3/NOPB directly replace FT531JA without circuit modifications?

A: Yes. The LP5907MFX-3.3/NOPB is pin-compatible in SOT-23-5 package, delivers identical 3.3V output at 250mA, and includes enable control and overcurrent protection. Superior performance characteristics (lower dropout voltage, improved PSRR, lower quiescent current) require no design changes.

Q: What is the key difference between NCP163ASN330T1G and LP5907MFX-3.3/NOPB?

A: Both are direct equivalents with identical electrical specifications. NCP163ASN330T1G includes soft start protection and achieves marginally lower quiescent current (20 µA vs. 25 µA). Selection depends on availability and soft start feature requirement.

Q: Why does XC6219A332MR-G have a different package designation (SOT-25-5 vs. SOT-23-5)?

A: XC6219A332MR-G uses SOT-25-5 package, which is physically compatible with SOT-23-5 footprints in most applications. However, pin spacing and dimensions differ slightly. Verify PCB layout compatibility before substitution.

Q: Is S-1132B33-M5T1U suitable for battery-powered applications?

A: Yes. The S-1132B33-M5T1U is specifically advantageous for battery-powered designs due to ultra-low quiescent current (1 µA), minimizing standby power consumption. The 300mA output current capability provides additional design margin.

Q: Can AP2139AK-3.3TRG1 be used in low-dropout applications?

A: No. The AP2139AK-3.3TRG1 exhibits 0.6V dropout voltage at 250mA, significantly higher than FT531JA (0.12V @ 100mA). This device is suitable only for applications with input voltage headroom exceeding 4V.

Q: What compliance certifications are critical for substitute selection?

A: All recommended substitutes carry ROHS3 compliance and REACH Unaffected status, matching FT531JA regulatory requirements. MSL (Moisture Sensitivity Level) ratings vary; most substitutes are MSL-1, while AP2139AK-3.3TRG1 is MSL-3, requiring appropriate moisture control during storage and assembly.

Q: Are there supply chain advantages to selecting specific substitutes?

A: LP5907MFX-3.3/NOPB and AP2139AK-3.3TRG1 show highest inventory availability (332,400 and 21,100 units respectively). NCP163ASN330T1G and S-1132B33-M5T1U have lower stock levels (1,283 and 2,074 units). REG102NA-3.3/3K carries Last Time Buy status, indicating limited future availability.

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