FT533DA Linear Voltage Regulator IC Equivalent & Substitute Parts

Part Overview

The FT533DA is a linear voltage regulator IC manufactured by Fremont Micro Devices Ltd, designed for positive fixed 1.8V output at 400mA in SOT-23-5 surface mount packaging. This device is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity. The FT533DA operates across -40°C to 85°C with integrated over-current protection and enable control features, suitable for low-power applications requiring stable 1.8V regulation.

Key Parameters

Parameter	FT533DA Specification
Manufacturer	Fremont Micro Devices Ltd
Category	Power Management (PMIC)
Output Voltage (Fixed)	1.8V
Output Current	400mA
Input Voltage (Max)	6V
Dropout Voltage	0.65V @ 400mA (Typ)
Quiescent Current	65 µA
Package	SOT-23-5 (SC-74A)
Operating Temperature	-40°C ~ 85°C
Control Features	Enable
Protection Features	Over Current
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution for the FT533DA is determined by strict alignment of the following electrical and mechanical parameters:

Primary Substitution Criteria:

Output voltage: 1.8V fixed
Package type: SOT-23-5 (SC-74A, SOT-753)
Output current capability: minimum 300mA (FT533DA rated at 400mA)
Input voltage range: maximum 6V or higher
Operating temperature range: -40°C to 85°C minimum
Output configuration: Positive fixed
Number of regulators: Single output

Secondary Compatibility Factors:

Dropout voltage performance at rated current
Quiescent current consumption
Control and protection feature availability
Surface mount mounting type

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

Group 1 (300mA Output): AP2125K-1.8TRE1, AP2125K-1.8TRG1, AP2127K-1.8TRG1 — Active status alternatives with reduced output current but matching voltage and package specifications.

Group 2 (500mA+ Output): BU18SD5WG-TL, RT9013-18GB — Higher current capacity alternatives with enhanced performance characteristics.

Group 3 (Low Current Specialized): MIC5232-1.8YD5-TR — Ultra-low quiescent current variant for battery-powered applications, with reduced output current rating.

Group 4 (Voltage Variant): AP2127K-1.5TRG1 — Alternative output voltage (1.5V) for applications not requiring 1.8V regulation.

Parameter Comparison

Parameter	FT533DA	AP2125K-1.8TRE1	AP2125K-1.8TRG1	AP2127K-1.8TRG1	BU18SD5WG-TL	MIC5232-1.8YD5-TR	RT9013-18GB
Manufacturer	Fremont Micro Devices Ltd	Diodes Incorporated	Diodes Incorporated	Diodes Incorporated	Rohm Semiconductor	Microchip Technology	Richtek USA Inc.
Output Voltage	1.8V	1.8V	1.8V	1.8V	1.8V	1.8V	1.8V
Output Current	400mA	300mA	300mA	300mA	500mA	10mA	500mA
Input Voltage (Max)	6V	6V	6V	6V	6V	7V	5.5V
Dropout Voltage	0.65V @ 400mA	0.36V @ 300mA	0.36V @ 300mA	0.7V @ 300mA	0.29V @ 100mA	0.3V @ 10mA	0.4V @ 500mA
Quiescent Current	65 µA	90 µA	90 µA	90 µA	80 µA	3 µA	50 µA
Package	SOT-23-5	SOT-23-5	SOT-23-5	SOT-23-5	5-SSOP	TSOT-23-5	SOT-23-5
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 105°C	-40°C ~ 125°C	-40°C ~ 85°C
Control Features	Enable	Enable	Enable	—	ON/OFF	Enable	Enable
Protection Features	Over Current	Over Current, Over Temperature	Over Current, Over Temperature	Over Current, Over Temperature	Over Current, Over Temperature	Reverse Polarity	Over Current, Over Temperature
Product Status	Obsolete	Active	Active	Active	Active	Active	Active
RoHS Status	—	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

For Direct Replacement (400mA Requirement):

RT9013-18GB and BU18SD5WG-TL both provide 500mA output current, exceeding the FT533DA's 400mA specification. RT9013-18GB maintains active product status with ROHS3 compliance and operates within the -40°C to 85°C temperature range. BU18SD5WG-TL extends operating temperature to 105°C and offers improved dropout voltage performance at 0.29V @ 100mA, with ROHS3 compliance and unlimited moisture sensitivity rating.

For Current-Limited Applications (300mA Maximum):

AP2125K-1.8TRG1 is the primary active substitute with matching 1.8V output, SOT-23-5 package, and -40°C to 85°C operating range. This part provides superior dropout voltage (0.36V @ 300mA) and includes over-temperature protection. AP2125K-1.8TRE1 offers identical electrical specifications with alternative packaging. AP2127K-1.8TRG1 maintains compatibility but lacks enable control features.

For Low-Power Applications:

MIC5232-1.8YD5-TR is suitable only for applications requiring maximum 10mA output current. This part offers exceptional quiescent current of 3 µA, extended operating temperature to 125°C, and ROHS3 compliance. Package variant is TSOT-23-5 (thin SOT-23-5).

Compliance and Availability:

All active substitute parts carry ROHS3 compliance and REACH unaffected status. RT9013-18GB has the highest inventory availability (105,300 pcs), followed by AP2125K-1.8TRG1 (92,525 pcs). All substitutes are manufactured by established semiconductor suppliers with active product status, ensuring long-term availability and technical support.

Frequently Asked Questions (FAQ)

Q: Can AP2125K-1.8TRG1 directly replace FT533DA in all applications?

A: AP2125K-1.8TRG1 is compatible for applications drawing up to 300mA. The FT533DA is rated for 400mA, so this substitute is suitable only if your circuit's maximum current draw does not exceed 300mA. Both parts share identical 1.8V output voltage, SOT-23-5 package, and -40°C to 85°C operating range.

Q: What is the difference between RT9013-18GB and BU18SD5WG-TL?

A: Both provide 500mA output current and 1.8V regulation. RT9013-18GB operates to 85°C with 0.4V dropout @ 500mA and 50 µA quiescent current. BU18SD5WG-TL extends to 105°C with superior 0.29V dropout @ 100mA and 80 µA quiescent current. BU18SD5WG-TL uses 5-SSOP package instead of SOT-23-5, requiring PCB layout modification.

Q: Is MIC5232-1.8YD5-TR suitable for my 400mA application?

A: No. MIC5232-1.8YD5-TR is rated for maximum 10mA output current and is designed for ultra-low-power applications. It is not suitable for 400mA loads.

Q: Why does AP2127K-1.8TRG1 lack enable control features?

A: AP2127K-1.8TRG1 is designed as a fixed-output regulator without enable pin functionality. If your circuit requires enable/disable control, use AP2125K-1.8TRG1, RT9013-18GB, or BU18SD5WG-TL instead.

Q: Can I use a substitute with higher maximum input voltage than 6V?

A: Yes. MIC5232-1.8YD5-TR accepts up to 7V input. However, verify that your circuit's input voltage does not exceed the substitute part's maximum rating. Higher input voltage capability does not affect compatibility if your actual input voltage remains within both the original and substitute specifications.

Q: What is the impact of different dropout voltages on my design?

A: Dropout voltage determines the minimum input-to-output voltage differential required for regulation. FT533DA requires 0.65V headroom @ 400mA. Substitutes with lower dropout voltage (AP2125K at 0.36V, BU18SD5WG-TL at 0.29V) allow operation with lower input voltages or provide better efficiency. Higher dropout voltage (AP2127K at 0.7V) requires greater input voltage margin.

Q: Are all substitutes RoHS compliant?

A: Yes. All active substitute parts listed carry ROHS3 compliance certification. The original FT533DA compliance status is not specified in available documentation.

Q: What packaging considerations apply to BU18SD5WG-TL?

A: BU18SD5WG-TL uses 5-SSOP package instead of SOT-23-5. While both are surface mount, pin configuration and PCB footprint differ. Verify PCB layout compatibility before selecting this substitute. All other substitutes maintain SOT-23-5 or TSOT-23-5 (thin variant) compatibility.

Q: Which substitute offers the best quiescent current performance?

A: MIC5232-1.8YD5-TR provides 3 µA quiescent current, significantly lower than FT533DA's 65 µA. For applications prioritizing low standby power consumption, this part is optimal if output current requirements do not exceed 10mA. RT9013-18GB offers 50 µA for higher-current applications.

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