CLL4733A TR Zener Diode 5.1V 1W MELF Equivalent & Substitute Parts

Part Overview

The CLL4733A TR is a surface mount Zener diode manufactured by Central Semiconductor Corp, rated at 5.1 V nominal voltage with 1 W maximum power dissipation in MELF (DO-213AB) package. This component is classified as obsolete, necessitating identification of active equivalent and substitute parts for ongoing design support and procurement continuity. Substitute parts must maintain electrical compatibility across voltage regulation, power handling, and thermal operating ranges while accommodating packaging and tolerance variations.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	5.1	V
Tolerance	±5%	—
Power - Max	1	W
Impedance (Max)	7	Ohms
Current - Reverse Leakage @ Vr	10	µA @ 1 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 eligibility is determined by the following critical parameters:

Primary Criteria (Must Match):

Voltage - Zener (Nom): 5.1 V
Mounting Type: Surface Mount
Package / Case: DO-213AB or MELF equivalent
Moisture Sensitivity Level: 1 (Unlimited)

Secondary Criteria (Allowable Variation):

Tolerance: ±5% (primary), ±10% or ±2% acceptable with design verification
Power - Max: 1 W (minimum), 1.25 W acceptable as higher rating
Impedance (Max): 7 Ohms (primary), 4 Ohms acceptable as lower impedance
Current - Reverse Leakage: 10 µA @ 1 V (primary), lower values acceptable
Operating Temperature: -65°C to 200°C (primary), -65°C to 175°C acceptable for most applications
Voltage - Forward (Vf): 1.2 V @ 200 mA (consistent across all parts)

Substitute parts are grouped by tolerance class and power rating to facilitate selection based on application requirements.

Parameter Comparison

Part Number	Manufacturer	Vz (Nom)	Tolerance	Power (Max)	Zzt (Max)	Ir @ Vr	Vf (Max)	Temp Range	Status
CLL4733A TR	Central Semiconductor	5.1 V	±5%	1 W	7 Ω	10 µA @ 1 V	1.2 V @ 200 mA	-65 to 200°C	Obsolete
1N4733AUR	Microchip Technology	5.1 V	±5%	1 W	7 Ω	10 µA @ 1 V	1.2 V @ 200 mA	-65 to 175°C	Active
1N5918BUR-1	Microchip Technology	5.1 V	±5%	1.25 W	4 Ω	5 µA @ 2 V	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL3826	Microchip Technology	5.1 V	±10%	1 W	7 Ω	3 µA @ 1 V	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL3826A	Microchip Technology	5.1 V	±5%	1 W	7 Ω	3 µA @ 1 V	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL4733	Microchip Technology	5.1 V	±10%	—	7 Ω	5 µA @ 1 V	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL4733A	Microchip Technology	5.1 V	±5%	—	7 Ω	5 µA @ 1 V	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL5918B	Microchip Technology	5.1 V	±5%	1.25 W	4 Ω	5 µA @ 2 V	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL5918C	Microchip Technology	5.1 V	±2%	1.25 W	4 Ω	5 µA @ 2 V	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL5918D	Microchip Technology	5.1 V	±1%	1.25 W	4 Ω	5 µA @ 2 V	1.2 V @ 200 mA	-65 to 175°C	Active

Engineering Selection Recommendations

Direct Equivalent (Highest Compatibility):

1N4733AUR is the primary direct equivalent to CLL4733A TR. Both parts share identical electrical specifications: 5.1 V nominal voltage, ±5% tolerance, 1 W power rating, and 7 Ohms maximum impedance. The only difference is operating temperature range (-65 to 175°C versus -65 to 200°C). This part is manufactured by Microchip Technology and carries active product status, ensuring long-term availability and supply chain stability.

Higher Power Alternatives (1.25 W Rating):

1N5918BUR-1, CDLL5918B, CDLL5918C, and CDLL5918D provide increased power dissipation capacity at 1.25 W with improved impedance characteristics (4 Ohms). These parts are suitable for applications requiring thermal margin or higher current handling. Tolerance options range from ±5% to ±1%, accommodating precision requirements. All are active products from Microchip Technology.

Tolerance Variants (±10% and ±5%):

CDLL3826 and CDLL4733 offer ±10% tolerance with 1 W power rating, suitable for applications with relaxed voltage regulation requirements. CDLL3826A and CDLL4733A provide ±5% tolerance matching the original specification. These parts feature lower reverse leakage characteristics (3 to 5 µA) compared to the original 10 µA specification.

Precision Grade (±1% and ±2%):

CDLL5918C (±2%) and CDLL5918D (±1%) are available for applications requiring tight voltage regulation. Both combine enhanced tolerance with 1.25 W power rating and 4 Ohms impedance.

All substitute parts maintain DO-213AB/MELF packaging compatibility, surface mount configuration, and MSL 1 moisture sensitivity rating. Operating temperature range of -65 to 175°C is acceptable for most industrial and commercial applications where the original -65 to 200°C specification is not explicitly required.

Frequently Asked Questions (FAQ)

Q: Can I use 1N4733AUR as a direct replacement for CLL4733A TR?

A: Yes. 1N4733AUR is electrically and mechanically equivalent with identical voltage (5.1 V), tolerance (±5%), power rating (1 W), and impedance (7 Ohms). The operating temperature range differs (-65 to 175°C versus -65 to 200°C), which is acceptable for applications not requiring operation above 175°C.

Q: What is the difference between 1 W and 1.25 W rated parts?

A: Power rating indicates maximum continuous power dissipation capability. 1.25 W parts (1N5918BUR-1, CDLL5918B, CDLL5918C, CDLL5918D) provide 25% additional thermal headroom. These parts also feature lower impedance (4 Ohms versus 7 Ohms), resulting in improved voltage regulation under load. Use 1.25 W parts when thermal margin or lower output impedance is required.

Q: What does tolerance (±5%, ±10%, ±1%) mean for Zener diodes?

A: Tolerance specifies the allowable deviation of the Zener voltage from the nominal 5.1 V specification. ±5% tolerance means the actual voltage will be between 4.845 V and 5.355 V. Tighter tolerances (±1%, ±2%) are required for precision voltage regulation applications. Looser tolerances (±10%) are acceptable for general-purpose applications.

Q: Are all substitute parts in the same MELF package?

A: Yes. All substitute parts use DO-213AB/MELF surface mount package, ensuring mechanical and thermal compatibility with the original CLL4733A TR footprint.

Q: What is impedance (Zzt) and why does it matter?

A: Impedance is the dynamic resistance of the Zener diode under load changes. Lower impedance (4 Ohms in 1.25 W parts) provides better voltage regulation stability when load current varies. Higher impedance (7 Ohms in 1 W parts) is acceptable for applications with stable load conditions.

Q: Can I use parts with lower reverse leakage current?

A: Yes. Reverse leakage current (Ir) is the small current flowing through the Zener in reverse bias. Lower leakage values (3 µA in CDLL3826 versus 10 µA in CLL4733A TR) indicate better performance and are fully compatible. This is a beneficial characteristic, not a limitation.

Q: Why is CLL4733A TR marked as obsolete?

A: Obsolete status indicates the original manufacturer (Central Semiconductor Corp) has discontinued production. Active equivalent parts from Microchip Technology ensure continued availability and supply chain reliability for new designs and production runs.

Q: Which substitute should I choose for a new design?

A: For new designs, select based on application requirements: (1) Use 1N4733AUR for direct replacement with guaranteed long-term availability; (2) Use 1.25 W variants (1N5918BUR-1, CDLL5918B/C/D) if thermal margin or lower impedance is beneficial; (3) Use precision grades (CDLL5918D ±1%) for tight voltage regulation requirements.

Q: Are all substitute parts RoHS non-compliant like the original?

A: Yes. All listed substitute parts carry RoHS non-compliant status, matching the original CLL4733A TR specification. REACH status is unaffected for all parts.

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