FT533IA Linear Voltage Regulator 3V 400mA Equivalent & Substitute Parts

Part Overview

The FT533IA is a linear voltage regulator IC from Fremont Micro Devices Ltd, designed to deliver a fixed 3V output at up to 400mA in a compact SOT-23-5 surface mount package. This device features enable control and over-current protection, operating across the industrial temperature range of -40°C to 85°C. The FT533IA is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements.

Key Parameters

Parameter	FT533IA
Manufacturer	Fremont Micro Devices Ltd
Output Voltage (Fixed)	3V
Output Current	400mA
Input Voltage (Max)	6V
Voltage Dropout (Max)	0.42V @ 400mA
Quiescent Current	65 µA
Package	SOT-23-5 (SC-74A)
Control Features	Enable
Protection Features	Over Current
Operating Temperature	-40°C ~ 85°C
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution for the FT533IA is determined by the following critical parameters:

Output Voltage: Must be fixed at 3V
Package: Must be SOT-23-5 (SC-74A, SOT-753)
Output Current Capability: Minimum 400mA required for direct replacement
Input Voltage Range: Maximum input voltage of 5.5V to 10V acceptable
Mounting Type: Surface mount only
Control Features: Enable function required
Protection Features: Over-current protection required

Substitute parts are grouped into two categories based on output current capacity:

Category A - Full Current Rating (400mA): Parts with 400mA output current matching the FT533IA specification. These provide direct functional equivalence.

Category B - Reduced Current Rating (300mA): Parts with 300mA output current. These are suitable for applications where the full 400mA is not required, provided the design accommodates the lower current limit.

Parameter Comparison

Parameter	FT533IA	AP2125K-3.0TRE1	AP2125K-3.0TRG1	AP2127K-3.0TRG1	REG113NA-3/3K	TPS73630DBVR	TPS73630MDBVREP
Manufacturer	Fremont Micro Devices Ltd	Diodes Incorporated	Diodes Incorporated	Diodes Incorporated	Texas Instruments	Texas Instruments	Texas Instruments
Output Voltage	3V	3V	3V	3V	3V	3V	3V
Output Current	400mA	300mA	300mA	300mA	400mA	400mA	400mA
Input Voltage (Max)	6V	6V	6V	6V	10V	5.5V	5.5V
Voltage Dropout (Max)	0.42V @ 400mA	0.3V @ 300mA	0.3V @ 300mA	0.3V @ 300mA	0.41V @ 400mA	0.2V @ 400mA	0.2V @ 400mA
Quiescent Current	65 µA	90 µA	90 µA	90 µA	500 µA	550 µA	550 µA
PSRR	75dB (1kHz ~ 10kHz)	65dB (100Hz ~ 1kHz)	65dB (100Hz ~ 1kHz)	68dB ~ 54dB (100Hz ~ 10kHz)	65dB (120Hz)	58dB ~ 37dB (100Hz ~ 10kHz)	58dB ~ 37dB (100Hz ~ 10kHz)
Package	SOT-23-5	SOT-23-5	SOT-23-5	SOT-23-5	SOT-23-5	SOT-23-5	SOT-23-5
Control Features	Enable	Enable	Enable	None	Enable	Enable	Enable
Protection Features	Over Current	Over Current, Over Temperature	Over Current, Over Temperature	Over Current, Over Temperature	Over Current, Over Temperature	Over Current, Over Temperature, Reverse Polarity	Over Current, Over Temperature, Reverse Polarity
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 125°C	-55°C ~ 125°C
Product Status	Obsolete	Active	Active	Active	Last Time Buy	Active	Active
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level	1 (Unlimited)	3 (168 Hours)	3 (168 Hours)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

For Direct Replacement (400mA Output Current)

REG113NA-3/3K from Texas Instruments provides the closest functional match to the FT533IA with identical 400mA output current and 3V fixed output. However, REG113NA-3/3K is classified as Last Time Buy, indicating limited future availability. This part is suitable for existing designs requiring immediate substitution but should not be selected for new long-term production.

TPS73630DBVR and TPS73630MDBVREP from Texas Instruments both deliver 400mA output current with superior performance characteristics, including lower dropout voltage (0.2V vs 0.42V) and extended temperature range. TPS73630MDBVREP extends the operating range to -55°C to 125°C, providing broader environmental coverage. Both are Active products with full RoHS3 compliance and unlimited moisture sensitivity rating. TPS73630DBVR is limited to -40°C to 125°C. These parts are recommended for new designs requiring 400mA capability.

For Reduced Current Applications (300mA Output Current)

AP2125K-3.0TRG1 and AP2125K-3.0TRE1 from Diodes Incorporated provide 300mA output current in SOT-23-5 packaging. Both are Active products with RoHS3 compliance. AP2125K-3.0TRG1 is supplied in Tape & Reel packaging with 1554 units in stock. AP2125K-3.0TRE1 is available in alternative packaging with higher inventory (15710 units). These parts are suitable for applications where 300mA output current is sufficient.

AP2127K-3.0TRG1 from Diodes Incorporated also delivers 300mA output current with improved PSRR performance (68dB to 54dB across 100Hz to 10kHz). This part lacks enable control features, which may limit its applicability in designs requiring output enable/disable functionality. AP2127K-3.0TRG1 maintains unlimited moisture sensitivity rating and is an Active product.

Compliance and Availability

All substitute parts listed are RoHS3 compliant and REACH unaffected. TPS73630DBVR and TPS73630MDBVREP offer the most comprehensive protection features, including reverse polarity protection not present in the original FT533IA. For new production, TPS73630MDBVREP is the preferred choice due to its extended temperature range and active product status.

Frequently Asked Questions (FAQ)

Q: Can AP2125K-3.0TRG1 or AP2127K-3.0TRG1 directly replace FT533IA in existing designs?

A: These parts are functionally compatible only if the application does not require the full 400mA output current. Both deliver 300mA maximum output current, which is 75% of the FT533IA rating. If the design draws more than 300mA, these substitutes will not function properly. Additionally, AP2127K-3.0TRG1 lacks enable control features present in the FT533IA.

Q: What is the difference between TPS73630DBVR and TPS73630MDBVREP?

A: Both parts deliver identical electrical performance with 400mA output current and 0.2V dropout voltage. The primary difference is operating temperature range: TPS73630DBVR operates from -40°C to 125°C, while TPS73630MDBVREP extends to -55°C to 125°C. TPS73630MDBVREP is suitable for applications requiring extended low-temperature operation.

Q: Why is REG113NA-3/3K listed as Last Time Buy?

A: Last Time Buy status indicates the manufacturer has announced end-of-life for this product. While currently available in inventory (15328 units), future availability is not guaranteed. This part should be used only for existing production runs requiring immediate substitution, not for new designs.

Q: Are all substitute parts available in SOT-23-5 packaging?

A: Yes. All substitute parts listed are supplied in SOT-23-5 (SC-74A, SOT-753) surface mount packaging, matching the FT533IA package specification. Packaging variants (Tape & Reel, Cut Tape, Digi-Reel) differ by supplier format but maintain identical component specifications.

Q: What is the moisture sensitivity difference between FT533IA and substitute parts?

A: FT533IA and most substitute parts (AP2127K-3.0TRG1, REG113NA-3/3K, TPS73630DBVR, TPS73630MDBVREP) have MSL 1 (Unlimited), requiring no special moisture handling. AP2125K-3.0TRE1 and AP2125K-3.0TRG1 have MSL 3 (168 Hours), requiring moisture control during storage and handling per IPC-A-610 standards.

Q: Which substitute part has the lowest dropout voltage?

A: TPS73630DBVR and TPS73630MDBVREP both feature 0.2V dropout voltage at 400mA, compared to 0.42V for the FT533IA. This 52% reduction in dropout voltage improves efficiency and reduces heat dissipation in power-constrained applications.

Q: Can I use a 300mA substitute in a design originally specified for 400mA?

A: Only if the actual circuit current draw does not exceed 300mA. The output current rating represents the maximum safe continuous current. Exceeding this limit causes the regulator to enter current-limit protection, reducing output voltage and potentially causing circuit malfunction. Verify actual current requirements before selecting a reduced-current substitute.

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