FMKA140 Equivalent & Substitute Parts

Part Overview

The FMKA140 is a Schottky rectifier diode rated for 40 V DC reverse voltage and 1 A average rectified current in a DO-214AC (SMA) surface mount package. This component is classified as obsolete, indicating it has been discontinued by the manufacturer (onsemi). Locating functionally equivalent substitute parts is necessary for ongoing production, maintenance, and design continuity where this diode was previously specified.

Key Parameters

Parameter	Value
Voltage - DC Reverse (Vr) (Max)	40 V
Current - Average Rectified (Io)	1 A
Voltage - Forward (Vf) (Max) @ If	600 mV @ 1 A
Speed	Fast Recovery ≤ 500ns, > 200mA (Io)
Current - Reverse Leakage @ Vr	1 mA @ 40 V
Mounting Type	Surface Mount
Package / Case	DO-214AC, SMA
Operating Temperature - Junction	-65°C ~ 125°C
Technology	Schottky

Substitute Part Grouping Explanation

Substitution of the FMKA140 is determined by the following critical parameters:

Mandatory Matching Parameters:

Voltage - DC Reverse (Vr) (Max): 40 V minimum
Current - Average Rectified (Io): 1 A minimum
Technology: Schottky
Mounting Type: Surface Mount
Package / Case: DO-214AC (SMA) compatible

Allowable Variations:

Forward voltage (Vf) may vary within acceptable circuit design margins
Reverse leakage current may be lower than the original specification
Operating temperature range may be extended (higher maximum junction temperature is acceptable)
Product status may transition from obsolete to active

Substitute parts are grouped into two categories:

Category A - Direct Electrical Equivalents (40 V, 1 A): Parts with identical voltage and current ratings, including MBRA140T3G, B140-13-F, B140-M3/5AT, B140-M3/61T, B140Q-13-F, and RB160L-40TE25.

Category B - Higher Voltage or Current Rated Alternatives: Parts with voltage or current ratings exceeding the FMKA140 specification, including SS15 (50 V, 1 A), B150-13-F (50 V, 1 A), CDBA140SL-HF (40 V, 1.4 A), and RB056L-40TE25 (40 V, 3 A). These parts are electrically compatible in applications where the FMKA140 was used, as they provide equal or superior performance within the same package family.

Parameter Comparison

Part Number	Manufacturer	Vr (Max)	Io	Vf (Max) @ If	Reverse Leakage @ Vr	Tj (Operating)	Product Status	Package
FMKA140	onsemi	40 V	1 A	600 mV @ 1 A	1 mA @ 40 V	-65°C ~ 125°C	Obsolete	DO-214AC (SMA)
MBRA140T3G	onsemi	40 V	1 A	550 mV @ 1 A	500 µA @ 40 V	-55°C ~ 125°C	Active	DO-214AC (SMA)
SS15	Taiwan Semiconductor Corporation	50 V	1 A	750 mV @ 1 A	200 µA @ 50 V	-55°C ~ 150°C	Active	DO-214AC (SMA)
B140-13-F	Diodes Incorporated	40 V	1 A	500 mV @ 1 A	500 µA @ 40 V	-65°C ~ 150°C	Active	DO-214AC (SMA)
B140-M3/5AT	Vishay General Semiconductor - Diodes Division	40 V	1 A	520 mV @ 1 A	200 µA @ 40 V	-65°C ~ 150°C	Active	DO-214AC (SMA)
B140-M3/61T	Vishay General Semiconductor - Diodes Division	40 V	1 A	520 mV @ 1 A	200 µA @ 40 V	-65°C ~ 150°C	Active	DO-214AC (SMA)
B140Q-13-F	Diodes Incorporated	40 V	1 A	500 mV @ 1 A	500 µA @ 40 V	-65°C ~ 150°C	Active	DO-214AC (SMA)
B150-13-F	Diodes Incorporated	50 V	1 A	700 mV @ 1 A	500 µA @ 50 V	-65°C ~ 150°C	Active	DO-214AC (SMA)
CDBA140SL-HF	Comchip Technology	40 V	1.4 A	330 mV @ 1 A	1 mA @ 40 V	-50°C ~ 100°C	Active	DO-214AC (SMA)
RB056L-40TE25	Rohm Semiconductor	40 V	3 A	670 mV @ 3 A	50 µA @ 40 V	-55°C ~ 150°C	Not For New Designs	DO-214AC (SMA)
RB160L-40TE25	Rohm Semiconductor	40 V	1 A	550 mV @ 1 A	100 µA @ 40 V	-55°C ~ 150°C	Not For New Designs	DO-214AC (SMA)

Engineering Selection Recommendations

Primary Substitutes (Active Status, 40 V / 1 A Rating):

The following parts are recommended as direct replacements for the obsolete FMKA140:

B140-13-F (Diodes Incorporated): Active product status with extended operating temperature range (-65°C ~ 150°C). Forward voltage of 500 mV @ 1 A is lower than the original specification, reducing power dissipation. RoHS3 compliant.
B140Q-13-F (Diodes Incorporated): Active product with automotive qualification (AEC-Q101). Identical electrical characteristics to B140-13-F with extended temperature range. Suitable for applications requiring automotive-grade components.
B140-M3/5AT and B140-M3/61T (Vishay General Semiconductor - Diodes Division): Active products with forward voltage of 520 mV @ 1 A and extended operating temperature range (-65°C ~ 150°C). RoHS3 compliant.
MBRA140T3G (onsemi): Active product from the original manufacturer. Forward voltage of 550 mV @ 1 A with reduced reverse leakage (500 µA @ 40 V). RoHS3 compliant.
RB160L-40TE25 (Rohm Semiconductor): Marked as "Not For New Designs" but remains available. Electrical characteristics align with FMKA140 requirements.

Secondary Substitutes (Higher Voltage or Current Rating):

B150-13-F (Diodes Incorporated): 50 V / 1 A rating provides voltage margin above the 40 V requirement. Active status with RoHS3 compliance. Forward voltage of 700 mV @ 1 A.
SS15 (Taiwan Semiconductor Corporation): 50 V / 1 A rating with extended operating temperature range (-55°C ~ 150°C). Active status with RoHS3 compliance.
CDBA140SL-HF (Comchip Technology): 40 V / 1.4 A rating provides current margin. Active status with RoHS3 compliance. Forward voltage of 330 mV @ 1 A is significantly lower than the original specification.
RB056L-40TE25 (Rohm Semiconductor): 40 V / 3 A rating provides substantial current margin. Marked as "Not For New Designs."

Compliance Status:

All recommended active substitutes carry RoHS3 compliance and REACH Unaffected status, matching the regulatory profile of the original FMKA140. Moisture Sensitivity Level (MSL) is 1 (Unlimited) across all alternatives.

Frequently Asked Questions (FAQ)

Q: Can I use a 50 V rated diode (SS15 or B150-13-F) in place of the 40 V FMKA140?

A: Yes. A higher voltage rating is electrically compatible in applications where the FMKA140 was specified. The 50 V diodes will operate safely at voltages up to 40 V and provide additional voltage margin for circuit protection.

Q: What is the difference between the B140-13-F and B140Q-13-F?

A: Both parts are manufactured by Diodes Incorporated with identical electrical specifications (40 V, 1 A, 500 mV Vf @ 1 A). The B140Q-13-F carries automotive qualification (AEC-Q101), making it suitable for automotive applications. Select B140Q-13-F if automotive-grade certification is required.

Q: Can I use CDBA140SL-HF, which has a 1.4 A rating, instead of the 1 A FMKA140?

A: Yes. The CDBA140SL-HF is electrically compatible and provides current margin. However, note that its operating temperature range (-50°C ~ 100°C) is narrower than the FMKA140 (-65°C ~ 125°C). Verify that the reduced temperature range is acceptable for your application.

Q: Why are some substitute parts marked "Not For New Designs"?

A: Parts marked "Not For New Designs" (RB056L-40TE25 and RB160L-40TE25) are still available in inventory but are being phased out by their manufacturers. These parts are suitable for replacement and maintenance of existing designs but should not be selected for new product development.

Q: Are all substitute parts available in the same DO-214AC (SMA) package?

A: Yes. All listed substitute parts use the DO-214AC (SMA) surface mount package, ensuring mechanical and electrical compatibility with the original FMKA140 footprint.

Q: What is the significance of forward voltage (Vf) differences among the substitutes?

A: Forward voltage affects power dissipation in the diode. Lower Vf values (such as B140-13-F at 500 mV) result in less heat generation compared to the original FMKA140 (600 mV). Higher Vf values (such as SS15 at 750 mV) result in greater heat generation. Select based on thermal design requirements of your circuit.

Q: Do all substitutes have the same reverse leakage current as the FMKA140?

A: No. The FMKA140 specifies 1 mA @ 40 V reverse leakage. Most substitutes have lower leakage (200 µA to 500 µA), which is beneficial for circuit performance. CDBA140SL-HF matches the original 1 mA specification. Lower leakage is generally acceptable and improves circuit characteristics.

Q: Which substitute offers the best overall compatibility with the FMKA140?

A: MBRA140T3G (onsemi) is the closest match, as it is from the original manufacturer and maintains the same 40 V / 1 A rating with similar electrical characteristics. B140-13-F and B140Q-13-F (Diodes Incorporated) are also excellent choices with active product status, extended temperature range, and lower forward voltage.

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