CMSH2-40LBK Equivalent & Substitute Parts

Part Overview

The CMSH2-40LBK is a Schottky diode manufactured by Central Semiconductor Corp, rated for 40 V DC reverse voltage and 2 A average rectified current in a Surface Mount SMB (DO-214AA) package. This part is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

The CMSH2-40LBK operates across a junction temperature range of -65°C to 150°C with fast recovery characteristics (≤500 ns for currents >200 mA). The forward voltage drop is specified at 400 mV @ 2 A, with reverse leakage current of 500 µA @ 40 V.

Key Parameters

Parameter	Value	Unit
Voltage - DC Reverse (Vr) (Max)	40	V
Current - Average Rectified (Io)	2	A
Voltage - Forward (Vf) (Max) @ If	400 mV @ 2 A	mV
Speed	Fast Recovery ≤500 ns, >200 mA (Io)	ns
Current - Reverse Leakage @ Vr	500	µA @ 40 V
Capacitance @ Vr, F	200	pF @ 4V, 1MHz
Package / Case	DO-214AA, SMB
Operating Temperature - Junction	-65 to 150	°C
Moisture Sensitivity Level (MSL)	1 (Unlimited)
Technology	Schottky

Substitute Part Grouping Explanation

Substitution of the CMSH2-40LBK is determined by the following critical parameters:

Primary Substitution Criteria:

Voltage - DC Reverse (Vr) (Max): Must equal or exceed 40 V
Current - Average Rectified (Io): Must equal or exceed 2 A
Technology: Schottky diode
Package / Case: DO-214AA, SMB (for direct mechanical and electrical compatibility)
Mounting Type: Surface Mount

Secondary Compatibility Factors:

Forward voltage (Vf): Lower values indicate improved efficiency; values up to 500 mV @ rated current are acceptable
Reverse leakage current: Lower values indicate better performance; up to 500 µA @ 40 V is acceptable
Operating temperature range: Must support -65°C to 150°C junction temperature
Speed characteristics: Fast recovery ≤500 ns for >200 mA is required

Substitute parts are grouped into three categories:

Direct Equivalents (2 A, SMB package): Parts with identical 40 V / 2 A ratings in SMB packaging
Higher Current Alternatives (3 A, SMB package): Parts with 40 V / 3 A ratings in SMB packaging, suitable for applications with current margin requirements
Lower Current Alternatives (1 A, SMB package): Parts with 40 V / 1 A ratings, suitable only for applications with reduced current requirements
Package Variant (2 A, SMA package): Part with identical electrical ratings but different mechanical package (SMA instead of SMB)

Parameter Comparison

Manufacturer Part Number	Manufacturer	Vr (Max) [V]	Io [A]	Vf (Max) [mV]	Package	Product Status	Compliance
CMSH2-40LBK	Central Semiconductor Corp	40	2	400 @ 2A	DO-214AA, SMB	Obsolete	MSL 1
B140BQ-13-F	Diodes Incorporated	40	1	500 @ 1A	DO-214AA, SMB	Active	AEC-Q101, ROHS3
B240-13-F	Diodes Incorporated	40	2	500 @ 2A	DO-214AA, SMB	Active	ROHS3
B240A-13-F	Diodes Incorporated	40	2	500 @ 2A	DO-214AC, SMA	Active	ROHS3
B240Q-13-F	Diodes Incorporated	40	2	500 @ 2A	DO-214AA, SMB	Active	AEC-Q101, ROHS3
B340BQ-13-F	Diodes Incorporated	40	3	500 @ 3A	DO-214AA, SMB	Active	AEC-Q101, ROHS3
B340LB-E3/52T	Vishay General Semiconductor	40	3	450 @ 3A	DO-214AA, SMB	Active	ROHS3
B340LB-E3/5BT	Vishay General Semiconductor	40	3	450 @ 3A	DO-214AA, SMB	Active	ROHS3
B340LB-M3/52T	Vishay General Semiconductor	40	3	450 @ 3A	DO-214AA, SMB	Active	ROHS3
B340LB-M3/5BT	Vishay General Semiconductor	40	3	450 @ 3A	DO-214AA, SMB	Active	ROHS3
SK14-TP	Micro Commercial Co	40	1	600 @ 1A	DO-214AA, SMB	Active	ROHS3

Engineering Selection Recommendations

Direct Replacement (Recommended for Obsolete Part Substitution):

B240-13-F and B240Q-13-F are the primary direct replacements for CMSH2-40LBK. Both parts maintain identical electrical specifications (40 V, 2 A, SMB package) with active product status. B240Q-13-F includes AEC-Q101 automotive qualification, providing additional reliability assurance. Both are ROHS3 compliant. The forward voltage specification of 500 mV @ 2 A is slightly higher than the original 400 mV, but remains within acceptable operating parameters for most applications.

Higher Current Alternative:

B340BQ-13-F, B340LB-E3/52T, B340LB-E3/5BT, B340LB-M3/52T, and B340LB-M3/5BT provide 3 A current rating in the same SMB package. These parts are suitable for applications requiring current margin or where future design upgrades may increase current demands. The Vishay B340LB series offers lower forward voltage (450 mV @ 3 A) compared to the Diodes B340BQ-13-F (500 mV @ 3 A). All are ROHS3 compliant and active products.

Package Variant:

B240A-13-F provides identical electrical specifications (40 V, 2 A) but in SMA package (DO-214AC) instead of SMB. This part is suitable only if PCB layout permits SMA package substitution.

Lower Current Alternative:

B140BQ-13-F and SK14-TP are 1 A rated parts suitable only for applications with reduced current requirements below 2 A. B140BQ-13-F includes AEC-Q101 qualification. SK14-TP has higher forward voltage (600 mV @ 1 A) and lower operating temperature range (-55°C to 125°C).

All recommended substitutes are active products with ROHS3 compliance and MSL 1 rating, ensuring long-term availability and environmental compliance.

Frequently Asked Questions (FAQ)

Q: Can B240-13-F directly replace CMSH2-40LBK without circuit modification?

A: Yes. B240-13-F maintains identical voltage (40 V) and current (2 A) ratings with the same SMB package. The forward voltage difference (500 mV vs. 400 mV) is a minor specification variance that does not require circuit redesign for most applications. Both parts are Schottky diodes with fast recovery characteristics.

Q: What is the difference between B240-13-F and B240Q-13-F?

A: Both parts have identical electrical specifications (40 V, 2 A, SMB). The primary difference is packaging: B240-13-F is supplied in Cut Tape (CT) & Digi-Reel format, while B240Q-13-F is supplied in Tape & Reel (TR) format. B240Q-13-F includes AEC-Q101 automotive qualification. Select based on procurement format requirements and application qualification needs.

Q: Why would I choose a 3 A part (B340 series) over a 2 A part (B240 series)?

A: The 3 A rated parts provide current margin for applications where design evolution or worst-case operating conditions may approach 2 A. They also offer lower forward voltage in the Vishay B340LB series (450 mV vs. 500 mV), reducing power dissipation. However, they are not required for applications strictly limited to 2 A operation.

Q: Is the SMA package variant (B240A-13-F) compatible with SMB PCB layouts?

A: No. SMA (DO-214AC) and SMB (DO-214AA) are different mechanical packages with different footprints. B240A-13-F requires PCB layout modification and cannot be used as a direct drop-in replacement for SMB-packaged designs.

Q: What does AEC-Q101 qualification mean?

A: AEC-Q101 is an automotive industry qualification standard for discrete semiconductors. Parts with this qualification (B140BQ-13-F, B240Q-13-F, B340BQ-13-F) have undergone additional reliability testing and are suitable for automotive and high-reliability applications. Non-qualified parts are suitable for general industrial and consumer applications.

Q: Can I use SK14-TP (1 A) in a circuit designed for 2 A operation?

A: No. SK14-TP is rated for maximum 1 A average rectified current. Using it in a 2 A application exceeds its current rating and will cause excessive heat generation and potential device failure. Use only in applications with confirmed current requirements below 1 A.

Q: What is the significance of the forward voltage difference between CMSH2-40LBK (400 mV) and substitute parts (450-600 mV)?

A: Forward voltage affects power dissipation and voltage drop across the diode. Higher forward voltage results in greater power loss. For most rectification and switching applications, the difference between 400 mV and 500 mV is acceptable. However, in precision analog circuits or high-efficiency designs, verify that the higher forward voltage does not exceed circuit tolerance limits.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All recommended substitute parts listed are ROHS3 compliant, meeting environmental and hazardous substance restrictions. The original CMSH2-40LBK does not specify ROHS status due to its obsolete classification.

Q: What is MSL 1 (Unlimited) moisture sensitivity?

A: MSL 1 indicates the lowest moisture sensitivity level, meaning the part has unlimited shelf life and does not require special moisture-controlled storage or handling. All substitute parts maintain MSL 1 rating, ensuring compatibility with standard component storage and assembly processes.

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