Equivalent & Substitute Parts for CLL4728A BK Zener Diode

Part Overview

The CLL4728A BK is a 3.3 V, 1 W surface mount Zener diode manufactured by Central Semiconductor Corp in MELF (DO-213AB) package format. This component is classified as obsolete, which necessitates identification of active equivalent and substitute parts for ongoing design support and procurement continuity. 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 in surface mount assemblies.

Key Parameters

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

Substitute Part Grouping Explanation

Substitution of the CLL4728A BK is determined by the following critical parameters:

Primary Substitution Criteria:

Zener voltage: 3.3 V nominal
Package format: DO-213AB / MELF surface mount
Mounting type: Surface mount
Impedance (maximum): 10 Ohms
Current - Reverse leakage @ Vr: 100 µA @ 1 V
Voltage - Forward (maximum) @ If: 1.2 V @ 200 mA

Secondary Substitution Criteria:

Tolerance: ±5% (exact match preferred; ±10% acceptable with design verification)
Power rating: 1 W minimum (higher ratings acceptable)
Operating temperature: -65°C to 175°C minimum (original part extends to 200°C)

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

Category 1: Exact Power Rating (1 W) with Matching Tolerance (±5%)

CDLL3821A: 1 W, ±5% tolerance, active status
CDLL4728A: 1 W, ±5% tolerance, active status

Category 2: Exact Power Rating (1 W) with Relaxed Tolerance (±10%)

CDLL3821: 1 W, ±10% tolerance, active status
CDLL4728: 1 W, ±10% tolerance, active status

Category 3: Enhanced Power Rating (1.25 W or Higher) with Matching Tolerance (±5%)

1N5913BUR-1: 1.25 W, ±5% tolerance, active status
CDLL5913B: 1.25 W, ±5% tolerance, active status
CDLL5913C: 1.25 W, ±2% tolerance, active status
CDLL5913D: 1.25 W, ±1% tolerance, active status
CDLL6485: 1.5 W, ±5% tolerance, active status

Category 4: Reduced Power Rating (500 mW)

CDLL6312: 500 mW, ±5% tolerance, active status (not recommended for direct substitution)

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance	Power (W)	Zzt (Ohms)	Ir @ Vr (µA)	Vf @ If (V)	Temp Range (°C)	Status
CLL4728A BK	Central Semiconductor	3.3	±5%	1	10	100 @ 1V	1.2 @ 200mA	-65 to 200	Obsolete
CDLL3821A	Microchip Technology	3.3	±5%	1	10	100 @ 1V	1.2 @ 200mA	-65 to 175	Active
CDLL4728A	Microchip Technology	3.3	±5%	—	10	100 @ 1V	1.2 @ 200mA	-65 to 175	Active
CDLL3821	Microchip Technology	3.3	±10%	1	10	100 @ 1V	1.2 @ 200mA	-65 to 175	Active
CDLL4728	Microchip Technology	3.3	±10%	—	10	100 @ 1V	1.2 @ 200mA	-65 to 175	Active
1N5913BUR-1	Microchip Technology	3.3	±5%	1.25	10	100 @ 1V	1.2 @ 200mA	-65 to 175	Active
CDLL5913B	Microchip Technology	3.3	±5%	1.25	10	100 @ 1V	1.2 @ 200mA	-65 to 175	Active
CDLL5913C	Microchip Technology	3.3	±2%	1.25	10	100 @ 1V	1.2 @ 200mA	-65 to 175	Active
CDLL5913D	Microchip Technology	3.3	±1%	1.25	10	100 @ 1V	1.2 @ 200mA	-65 to 175	Active
CDLL6485	Microchip Technology	3.3	±5%	1.5	10	50 @ 1V	1 @ 200mA	-65 to 175	Active
CDLL6312	Microchip Technology	3.3	±5%	0.5	24	5 @ 1V	1.1 @ 200mA	-65 to 175	Active

Engineering Selection Recommendations

Primary Recommendation: CDLL3821A

CDLL3821A is the preferred direct substitute for CLL4728A BK. This part maintains identical electrical specifications (3.3 V, ±5% tolerance, 1 W power rating, 10 Ohms impedance, 100 µA reverse leakage) and operates in the same DO-213AB MELF package. The part is manufactured by Microchip Technology with active product status, ensuring long-term availability and supply chain stability. The operating temperature range extends to -65°C to 175°C, which covers the majority of industrial and commercial applications. Current inventory availability is 906 pieces.

Secondary Recommendation: CDLL4728A

CDLL4728A provides an alternative direct substitute with identical electrical performance and active status. This part carries the same base designation as the original CLL4728A BK, offering design continuity. Inventory availability is 1034 pieces.

Alternative for Relaxed Tolerance Applications: CDLL3821 or CDLL4728

When design specifications permit ±10% voltage tolerance instead of ±5%, CDLL3821 and CDLL4728 are acceptable substitutes. Both maintain 1 W power rating and identical impedance characteristics. CDLL3821 has 1182 pieces in stock and CDLL4728 has 1050 pieces in stock.

Enhanced Power Rating Options: 1N5913BUR-1, CDLL5913B, CDLL5913C, CDLL5913D

These parts provide 1.25 W power rating while maintaining 3.3 V nominal voltage and ±5% or tighter tolerance. Selection among these variants depends on tolerance requirements:

1N5913BUR-1 and CDLL5913B: ±5% tolerance (matching original specification)
CDLL5913C: ±2% tolerance (enhanced precision)
CDLL5913D: ±1% tolerance (highest precision)

Higher power ratings provide thermal margin in applications approaching the 1 W limit of the original part.

Not Recommended: CDLL6312

CDLL6312 operates at 500 mW power rating, which is insufficient for direct substitution in applications designed for 1 W dissipation. Additionally, this part exhibits different impedance (24 Ohms versus 10 Ohms) and reduced reverse leakage current (5 µA versus 100 µA), indicating different internal characteristics unsuitable for equivalent replacement.

Temperature Range Consideration

The original CLL4728A BK operates to 200°C. All active substitute parts operate to 175°C maximum. Applications requiring operation above 175°C require design review and alternative component selection outside this substitute list.

Compliance and Regulatory Status

All substitute parts carry RoHS non-compliant status and REACH Unaffected designation, matching the regulatory profile of the original part. ECCN classification is EAR99 for all parts. HTSUS code 8541.10.0050 applies uniformly across all substitutes.

Frequently Asked Questions (FAQ)

Q1: Can CDLL3821A directly replace CLL4728A BK without circuit modification?

Yes. CDLL3821A maintains identical electrical specifications across all critical parameters: 3.3 V nominal voltage, ±5% tolerance, 1 W power rating, 10 Ohms impedance, 100 µA reverse leakage current, and 1.2 V forward voltage at 200 mA. Both use DO-213AB MELF surface mount packaging. No circuit modification is required.

Q2: What is the difference between CDLL3821A and CDLL3821?

The primary difference is voltage tolerance. CDLL3821A specifies ±5% tolerance, matching the original CLL4728A BK specification. CDLL3821 specifies ±10% tolerance, which is relaxed. Both maintain identical power rating (1 W), impedance (10 Ohms), and other electrical characteristics. CDLL3821 is acceptable only when circuit design permits ±10% voltage variation.

Q3: Why are higher power rating parts (1.25 W, 1.5 W) listed as substitutes for a 1 W part?

Higher power ratings provide thermal margin and improved reliability in applications operating near the maximum power dissipation limit. A 1.25 W or 1.5 W part can safely handle the same 1 W load with lower junction temperature and extended operational life. These parts are electrically equivalent at the 1 W operating point and are suitable substitutes when enhanced thermal performance is beneficial.

Q4: Can CDLL6312 (500 mW) be used as a substitute?

No. CDLL6312 is not suitable for direct substitution. The 500 mW power rating is insufficient for applications designed around 1 W dissipation. Additionally, CDLL6312 exhibits different impedance (24 Ohms versus 10 Ohms) and different reverse leakage characteristics (5 µA versus 100 µA), indicating fundamentally different internal design unsuitable for equivalent replacement.

Q5: What is the impact of the reduced operating temperature range (175°C versus 200°C) in substitute parts?

All active substitute parts operate to -65°C to 175°C, compared to the original part's -65°C to 200°C range. For applications operating below 175°C, this difference is not significant. Applications requiring sustained operation above 175°C require alternative component selection outside this substitute list and design review to confirm thermal management adequacy.

Q6: Are all substitute parts available in the same MELF package?

Yes. All substitute parts listed use DO-213AB MELF surface mount package format, identical to the original CLL4728A BK. No PCB layout modification is required for package compatibility.

Q7: What is the inventory status for substitute parts?

Current inventory levels are: CDLL3821A (906 pcs), CDLL4728A (1034 pcs), CDLL3821 (1182 pcs), CDLL4728 (1050 pcs), 1N5913BUR-1 (763 pcs), CDLL5913B (999 pcs), CDLL5913C (990 pcs), CDLL5913D (1109 pcs), CDLL6485 (1111 pcs), and CDLL6312 (1006 pcs). All parts are classified as new original stock.

Q8: Do substitute parts have different RoHS or REACH compliance status?

All substitute parts carry identical regulatory status to the original CLL4728A BK: RoHS non-compliant and REACH Unaffected. ECCN classification is EAR99 and HTSUS code is 8541.10.0050 for all parts.

Q9: Which substitute part offers the best tolerance specification?

CDLL5913D offers the tightest tolerance at ±1%, followed by CDLL5913C at ±2%. Both maintain 3.3 V nominal voltage and 1.25 W power rating. These parts are suitable for precision voltage regulation applications requiring enhanced accuracy beyond the original ±5% specification.

Q10: Can multiple substitute parts be used interchangeably in the same design?

Yes, within the constraints of the specified tolerance and power rating requirements. Parts within the same tolerance and power rating category (e.g., all ±5% / 1 W parts) are electrically interchangeable. Parts from different categories (e.g., ±5% / 1 W versus ±10% / 1 W) should not be mixed in the same circuit without design verification, as tolerance differences may affect circuit performance.

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