CLL4728A TR Equivalent & Substitute Parts

Part Overview

The CLL4728A TR is a surface mount Zener diode manufactured by Central Semiconductor Corp, rated at 3.3 V nominal with 1 W maximum power dissipation and ±5% tolerance. This component is classified as obsolete, necessitating identification of active equivalent and substitute parts for ongoing design support and procurement continuity. Substitute parts are selected from Microchip Technology's active product line, maintaining electrical compatibility within specified parameter ranges.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	3.3	V
Tolerance	±5%	—
Power - Max	1	W
Impedance (Max)	10	Ohms
Current - Reverse Leakage @ Vr	100	µA @ 1 V
Voltage - Forward (Vf) (Max) @ If	1.2	V @ 200 mA
Operating Temperature Range	-65 to 200	°C
Mounting Type	Surface Mount	—
Package / Case	DO-213AB, MELF	—
Moisture Sensitivity Level	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitute parts are grouped based on electrical parameter compatibility with the CLL4728A TR. The primary substitution criteria are:

Critical Parameters (Must Match):

Voltage - Zener (Nom): 3.3 V
Mounting Type: Surface Mount
Package / Case: DO-213AB, MELF
Impedance (Max): 10 Ohms
Current - Reverse Leakage @ Vr: 100 µA @ 1 V
Voltage - Forward (Vf) (Max) @ If: 1.2 V @ 200 mA

Allowable Variations:

Tolerance: ±5% (main part) to ±10% (substitute acceptable)
Power - Max: 1 W (main part) to 1.5 W (substitute acceptable for higher power margin)
Operating Temperature: -65°C to 175°C (substitute) vs. -65°C to 200°C (main part)

Substitute parts are classified into three categories:

Category 1 - Direct Electrical Equivalents (1 W Power Rating): CDLL3821A, CDLL4728, CDLL4728A maintain the 1 W power specification with matching electrical characteristics.

Category 2 - Higher Power Variants (1.25 W - 1.5 W Power Rating): 1N5913BUR-1, CDLL5913B, CDLL5913C, CDLL5913D, CDLL6485 provide increased power dissipation capability while maintaining 3.3 V nominal voltage and core electrical parameters.

Category 3 - Lower Power Variant (500 mW Power Rating): CDLL6312 operates at reduced power with modified impedance and leakage specifications.

Parameter Comparison

Part Number	Manufacturer	Vz (Nom)	Tolerance	Power (Max)	Zzt (Max)	Ir @ Vr	Vf (Max) @ If	Temp Range	Status
CLL4728A TR	Central Semiconductor	3.3 V	±5%	1 W	10 Ω	100 µA @ 1 V	1.2 V @ 200 mA	-65 to 200°C	Obsolete
CDLL3821A	Microchip Technology	3.3 V	±5%	1 W	10 Ω	100 µA @ 1 V	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL3821	Microchip Technology	3.3 V	±10%	1 W	10 Ω	100 µA @ 1 V	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL4728	Microchip Technology	3.3 V	±10%	Not specified	10 Ω	100 µA @ 1 V	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL4728A	Microchip Technology	3.3 V	±5%	Not specified	10 Ω	100 µA @ 1 V	1.2 V @ 200 mA	-65 to 175°C	Active
1N5913BUR-1	Microchip Technology	3.3 V	±5%	1.25 W	10 Ω	100 µA @ 1 V	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL5913B	Microchip Technology	3.3 V	±5%	1.25 W	10 Ω	100 µA @ 1 V	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL5913C	Microchip Technology	3.3 V	±2%	1.25 W	10 Ω	100 µA @ 1 V	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL5913D	Microchip Technology	3.3 V	±1%	1.25 W	10 Ω	100 µA @ 1 V	1.2 V @ 200 mA	-65 to 175°C	Active
CDLL6485	Microchip Technology	3.3 V	±5%	1.5 W	10 Ω	50 µA @ 1 V	1 V @ 200 mA	-65 to 175°C	Active
CDLL6312	Microchip Technology	3.3 V	±5%	500 mW	24 Ω	5 µA @ 1 V	1.1 V @ 200 mA	-65 to 175°C	Active

Engineering Selection Recommendations

Primary Substitutes (Recommended for Direct Replacement):

CDLL3821A is the preferred direct substitute. It maintains identical electrical specifications to the CLL4728A TR, including 3.3 V nominal voltage, ±5% tolerance, 1 W power rating, and all critical electrical parameters. Product status is active with full availability. Operating temperature range is -65°C to 175°C, which covers standard industrial applications; the main part's extended upper limit of 200°C is not required for most circuit designs.

Secondary Substitutes (Acceptable with Design Verification):

CDLL4728A provides electrical equivalence with ±5% tolerance matching. Power rating specification is not provided in documentation; design review is required to confirm 1 W capability.

CDLL3821 is electrically compatible with relaxed ±10% tolerance specification. This part is suitable for applications where tolerance margin is acceptable.

Higher Power Alternatives (For Increased Thermal Margin):

1N5913BUR-1, CDLL5913B, CDLL5913C, and CDLL5913D provide 1.25 W power rating, offering 25% additional dissipation capacity. CDLL5913D offers ±1% tolerance for precision applications. These parts are suitable for designs requiring enhanced thermal performance or where power margin is beneficial.

CDLL6485 provides 1.5 W power rating with improved reverse leakage characteristics (50 µA vs. 100 µA). Forward voltage is reduced to 1 V at 200 mA, which may affect circuit behavior in voltage regulation applications.

Not Recommended for Direct Substitution:

CDLL6312 operates at 500 mW power rating with modified impedance (24 Ω vs. 10 Ω) and significantly reduced reverse leakage (5 µA vs. 100 µA). These parameter changes alter circuit behavior and require full design re-evaluation.

All substitute parts are manufactured by Microchip Technology with active product status, ensuring long-term availability and supply chain continuity.

Frequently Asked Questions (FAQ)

Q: Can CDLL3821A directly replace CLL4728A TR without circuit modification?

A: Yes. CDLL3821A maintains all critical electrical parameters: 3.3 V nominal voltage, ±5% tolerance, 1 W power rating, 10 Ω impedance, 100 µA reverse leakage, and 1.2 V forward voltage. Package compatibility (DO-213AB, MELF) is confirmed. Operating temperature range differs (-65°C to 175°C vs. -65°C to 200°C), but this does not affect standard industrial applications.

Q: What is the difference between CDLL3821A and CDLL3821?

A: Both parts are 3.3 V, 1 W Zener diodes in DO-213AB package. The primary difference is tolerance specification: CDLL3821A is ±5% (matching the original CLL4728A TR), while CDLL3821 is ±10%. Select CDLL3821A for applications requiring tighter voltage regulation; CDLL3821 is acceptable where tolerance margin is permissible.

Q: Why would I select a higher power variant like CDLL5913B instead of CDLL3821A?

A: Higher power variants (1.25 W or 1.5 W) provide increased thermal margin and extended operational life in applications with sustained power dissipation. They are suitable for designs where thermal stress is a concern or where future design modifications may increase power requirements. Electrical characteristics remain compatible with the original 1 W specification.

Q: Is CDLL6312 a suitable substitute?

A: CDLL6312 is not recommended for direct substitution. Although it maintains 3.3 V nominal voltage, it operates at 500 mW power rating (50% of the original), has modified impedance (24 Ω vs. 10 Ω), and significantly reduced reverse leakage (5 µA vs. 100 µA). These changes alter circuit behavior and require complete design re-evaluation and testing.

Q: Are all substitute parts RoHS compliant?

A: All Microchip Technology substitute parts listed are RoHS non-compliant. If RoHS compliance is required, alternative sourcing must be pursued outside this substitute list.

Q: What is the impact of operating temperature range differences?

A: The CLL4728A TR operates to 200°C; Microchip substitutes operate to 175°C. For standard industrial applications (-40°C to 85°C ambient), this difference is not significant. Applications requiring operation above 175°C require alternative component selection.

Q: Can I use CDLL5913D for precision voltage regulation applications?

A: Yes. CDLL5913D offers ±1% tolerance, providing superior voltage regulation accuracy compared to the original ±5% specification. It maintains 3.3 V nominal voltage, 1.25 W power rating, and all core electrical parameters. This part is suitable for precision analog circuits requiring tight voltage reference stability.

Q: Are package dimensions identical between CLL4728A TR and all substitutes?

A: All substitute parts use DO-213AB or MELF package designation, which are mechanically compatible. Confirm PCB footprint compatibility with component datasheets before final design release.

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