CLL4758A BK Zener Diode 56V 1W MELF Equivalent & Substitute Parts

Part Overview

The CLL4758A BK is a 56 V, 1 W Zener diode manufactured by Central Semiconductor Corp in Surface Mount MELF (DO-213AB) package. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The part operates across a temperature range of -65°C to 200°C with ±5% voltage tolerance and is suitable for voltage regulation and protection applications requiring precise 56 V reference levels.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	56	V
Tolerance	±5%	—
Power - Max	1	W
Impedance (Max)	110	Ohms
Current - Reverse Leakage @ Vr	5	µA @ 42.6 V
Voltage - Forward (Vf) (Max) @ If	1.2	V @ 200 mA
Operating Temperature	-65 to 200	°C
Mounting Type	Surface Mount	—
Package / Case	DO-213AB, MELF	—
Moisture Sensitivity Level	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the CLL4758A BK is determined by the following critical parameters:

Primary Substitution Criteria:

Zener voltage: 56 V nominal
Package / Case: DO-213AB or MELF (Surface Mount)
Mounting Type: Surface Mount
Voltage tolerance: ±5% or tighter
Operating temperature range: Must support -65°C minimum
Moisture Sensitivity Level: 1 (Unlimited)

Secondary Compatibility Factors:

Power rating: 1 W or higher
Impedance (Max): 110 Ohms or lower
Forward voltage: 1.2 V @ 200 mA or lower
Reverse leakage current: Acceptable within application requirements

Substitute parts are grouped into three categories based on power rating and tolerance specifications:

Group 1 - Direct 1 W Equivalents (±5% Tolerance): CDLL3038B, CDLL4758A Group 2 - Enhanced 1.25 W Alternatives (±5% or Tighter): 1N5943BUR-1, CDLL5943B, CDLL5943C, CDLL5943D Group 3 - Alternative Tolerance Options: 1N3038BUR-1 (±5%), CDLL3038 (±20%), CDLL4758 (±10%)

All substitute parts maintain the 56 V nominal zener voltage, DO-213AB package, and Surface Mount configuration required for direct replacement.

Parameter Comparison

Part Number	Manufacturer	Vz (Nom)	Tolerance	Power (Max)	Zzt (Max)	Vf (Max) @ If	Temp Range	Status
CLL4758A BK	Central Semiconductor	56 V	±5%	1 W	110 Ω	1.2 V @ 200 mA	-65 to 200°C	Obsolete
1N3038BUR-1	Microchip Technology	56 V	±5%	1 W	110 Ω	1.2 V @ 200 mA	-55 to 175°C	Active
1N5943BUR-1	Microchip Technology	56 V	±5%	1.25 W	86 Ω	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL3038	Microchip Technology	56 V	±20%	1 W	110 Ω	1.2 V @ 200 mA	-55 to 175°C	Active
CDLL3038B	Microchip Technology	56 V	±5%	1 W	110 Ω	1.2 V @ 200 mA	-55 to 175°C	Active
CDLL4758	Microchip Technology	56 V	±10%	Not specified	110 Ω	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL4758A	Microchip Technology	56 V	±5%	Not specified	110 Ω	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL5943B	Microchip Technology	56 V	±5%	1.25 W	86 Ω	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL5943C	Microchip Technology	56 V	±2%	1.25 W	86 Ω	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL5943D	Microchip Technology	56 V	±1%	1.25 W	86 Ω	1.2 V @ 200 mA	-65 to 175°C	Active

Engineering Selection Recommendations

Primary Recommendation for Direct Replacement:

CDLL4758A (Microchip Technology) is the closest functional equivalent to CLL4758A BK. Both parts share identical electrical specifications: 56 V nominal zener voltage, ±5% tolerance, 110 Ohms maximum impedance, and 1.2 V forward voltage. CDLL4758A maintains the full -65°C to 200°C operating temperature range of the original part and is currently in active production status, ensuring long-term availability.

Alternative for Enhanced Performance:

CDLL5943B or CDLL5943C (Microchip Technology) provide increased power dissipation capability (1.25 W versus 1 W) with lower impedance (86 Ohms versus 110 Ohms). These parts are suitable for applications requiring improved thermal performance or lower dynamic impedance. CDLL5943C offers ±2% tolerance for applications requiring tighter voltage regulation. Both maintain the -65°C minimum operating temperature and are in active production.

Secondary Options:

1N5943BUR-1 (Microchip Technology) is functionally equivalent to CDLL5943B with identical 1.25 W power rating and ±5% tolerance. Operating temperature range is -65°C to 175°C, which is acceptable for most applications but does not extend to 200°C.

1N3038BUR-1 (Microchip Technology) provides 1 W power rating with ±5% tolerance matching the original specification. Operating temperature range is -55°C to 175°C, which is narrower than the original part.

CDLL3038B (Microchip Technology) matches the 1 W power rating and ±5% tolerance with identical impedance. Operating temperature range is -55°C to 175°C.

Tolerance Trade-offs:

CDLL3038 (±20% tolerance) and CDLL4758 (±10% tolerance) are available for cost-sensitive applications where tighter voltage regulation is not required. These parts maintain active production status but offer reduced voltage accuracy compared to the original ±5% specification.

Compliance Considerations:

All substitute parts are RoHS non-compliant and REACH unaffected, matching the compliance profile of the original CLL4758A BK. All parts carry ECCN EAR99 and HTSUS 8541.10.0050 classifications. Moisture Sensitivity Level 1 (Unlimited) is maintained across all alternatives.

Frequently Asked Questions (FAQ)

Q: Can CDLL5943B replace CLL4758A BK in all applications?

A: CDLL5943B is electrically compatible with CLL4758A BK for the 56 V zener voltage and ±5% tolerance specification. The increased power rating (1.25 W versus 1 W) and lower impedance (86 Ohms versus 110 Ohms) provide enhanced performance margins. However, applications with strict thermal or impedance requirements should verify that the lower impedance does not affect circuit behavior. Both parts support the -65°C to 175°C operating range, though CDLL5943B does not extend to 200°C.

Q: What is the difference between CDLL4758A and CDLL5943B?

A: Both parts maintain 56 V nominal zener voltage and ±5% tolerance. The primary differences are: CDLL5943B has 1.25 W power rating versus 1 W for CDLL4758A, CDLL5943B has 86 Ohms maximum impedance versus 110 Ohms for CDLL4758A, and CDLL5943B has 1 µA reverse leakage current versus 100 nA for CDLL4758A. CDLL5943B is suitable for applications requiring higher power dissipation or lower dynamic impedance.

Q: Is the DO-213AB package identical to MELF?

A: DO-213AB and MELF refer to the same Surface Mount package format. Both designations describe the cylindrical metal electrode leadless face (MELF) package used for surface mount diodes. All substitute parts listed use this identical package, ensuring mechanical and electrical compatibility with the original CLL4758A BK footprint.

Q: Can I use a part with ±10% or ±20% tolerance instead of ±5%?

A: CDLL4758 (±10% tolerance) and CDLL3038 (±20% tolerance) are electrically compatible alternatives. However, applications requiring precise 56 V regulation should use parts with ±5% tolerance or tighter. The tolerance specification directly affects voltage accuracy in the circuit. Select tolerance based on application requirements for voltage regulation precision.

Q: What is the impact of lower impedance (86 Ohms versus 110 Ohms)?

A: Lower impedance in CDLL5943 series parts (86 Ohms) results in faster transient response and lower dynamic resistance compared to CLL4758A BK (110 Ohms). This improves voltage regulation under load changes. For most applications, lower impedance is beneficial. However, circuits with specific impedance-dependent behavior should be evaluated to confirm compatibility.

Q: Are all substitute parts currently in production?

A: Yes, all listed substitute parts carry Active product status from Microchip Technology, ensuring ongoing availability and supply chain reliability. The original CLL4758A BK is classified as Obsolete, making active production alternatives necessary for new designs and long-term support.

Q: What is the temperature range limitation for substitute parts?

A: CLL4758A BK operates from -65°C to 200°C. Most substitute parts operate from -65°C to 175°C, which covers the majority of industrial and commercial applications. Only 1N3038BUR-1 and CDLL3038B have a narrower range of -55°C to 175°C. Applications requiring operation above 175°C should confirm compatibility with the specific substitute part selected.

Q: Do all parts have the same moisture sensitivity level?

A: Yes, all substitute parts maintain Moisture Sensitivity Level 1 (Unlimited), identical to the original CLL4758A BK. This indicates no moisture sensitivity restrictions for storage, handling, or reflow soldering processes.

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