BZX55C6V8 Equivalent & Substitute Parts

Part Overview

The BZX55C6V8 is a 6.8 V Zener diode rated at 500 mW with ±6% tolerance, manufactured by onsemi in a through-hole DO-35 package. This component is classified as obsolete, indicating that direct procurement from the original manufacturer is no longer available. Identifying equivalent and substitute parts is necessary to maintain design continuity, ensure supply chain reliability, and support ongoing production or repair requirements for applications utilizing this Zener diode specification.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	6.8	V
Tolerance	±6%	-
Power - Max	500	mW
Impedance (Max)	8	Ohms
Current - Reverse Leakage @ Vr	100 nA @ 3 V	-
Voltage - Forward (Vf) (Max) @ If	1.3 V @ 100 mA	-
Operating Temperature	-65°C ~ 200°C	-
Mounting Type	Through Hole	-
Package / Case	DO-35 (DO-204AH)	-

Substitute Part Grouping Explanation

Substitution of the BZX55C6V8 is determined by the following critical parameters:

Primary Substitution Criteria:

Zener voltage: 6.8 V (nominal)
Power rating: 500 mW or higher
Package type: DO-35 (DO-204AH) for direct mechanical compatibility
Operating temperature range: -65°C minimum to 175°C or higher
Tolerance: ±5% or ±6%

Substitution Categories:

Direct Equivalents (Same Package, Same Power Rating): Parts with identical 6.8 V rating, 500 mW power dissipation, and DO-35 packaging provide pin-for-pin and footprint compatibility with no design modifications required.

Higher Power Alternatives (Same Package, Higher Power Rating): Parts with 6.8 V rating and power ratings exceeding 500 mW in DO-35 or compatible packages are functionally compatible but may introduce thermal design considerations.

Alternative Package Options (Same Electrical Specifications, Different Package): Parts with 6.8 V rating and 500 mW or higher power ratings in DO-7 or DO-41 packages require PCB layout modifications but maintain electrical compatibility.

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance	Power (mW)	Zzt (Ohms)	Package	Status	Temp Range (°C)
BZX55C6V8	onsemi	6.8	±6%	500	8	DO-35	Obsolete	-65 ~ 200
BZX79C6V8-T50A	Fairchild Semiconductor	6.8	±5%	500	15	DO-35	Active	-65 ~ 200
1N5235B	Microchip Technology	6.8	±5%	500	5	DO-35	Active	-65 ~ 175
BZX79C6V8	Taiwan Semiconductor Corporation	6.8	±5%	500	15	DO-35	Active	-65 ~ 175
1N957B-1	Microchip Technology	6.8	±5%	500	4.5	DO-35	Active	-65 ~ 175
1N4736A	Lumimax Optoelectronic Technology	6.8	±5%	1000	3.5	DO-41	Active	-65 ~ 200
1N5921BP-TP	Micro Commercial Co	6.8	±5%	1500	2.5	DO-41	Active	-55 ~ 175
1N957B	Microchip Technology	6.8	±5%	500	4.5	DO-7	Active	-65 ~ 175
2EZ6.8D5-TP	Micro Commercial Co	6.8	±5%	2000	2	DO-41	Active	-55 ~ 150

Engineering Selection Recommendations

For Direct Replacement (No Design Changes Required):

Select from parts with DO-35 packaging and 500 mW power rating: BZX79C6V8-T50A, 1N5235B, BZX79C6V8, or 1N957B-1. These provide identical footprint compatibility and electrical performance within the original design specifications. BZX79C6V8-T50A and BZX79C6V8 are active products with extended temperature range support to 200°C and 175°C respectively, ensuring long-term availability and thermal margin.

For Applications Requiring Higher Power Dissipation:

Parts rated at 1 W or higher (1N4736A, 1N5921BP-TP, 2EZ6.8D5-TP) accommodate increased thermal loads. These alternatives require PCB layout modifications due to different package geometries (DO-41 or DO-7) but provide improved thermal performance and lower impedance characteristics.

Compliance and Availability Considerations:

BZX79C6V8 (Taiwan Semiconductor Corporation) carries RoHS3 compliance certification. 1N5921BP-TP and 2EZ6.8D5-TP are RoHS3 compliant. 1N5235B and 1N957B are RoHS non-compliant. All parts maintain REACH Unaffected status. Active product status ensures ongoing supply chain availability for BZX79C6V8-T50A, 1N5235B, BZX79C6V8, 1N5921BP-TP, 1N957B, 1N957B-1, 1N4736A, and 2EZ6.8D5-TP.

Frequently Asked Questions (FAQ)

Q: Can BZX79C6V8-T50A directly replace BZX55C6V8 without PCB modifications?

A: Yes. BZX79C6V8-T50A shares identical DO-35 packaging and 500 mW power rating. The ±5% tolerance is tighter than the original ±6%, providing improved voltage regulation accuracy. Both support -65°C to 200°C operating range, ensuring thermal compatibility.

Q: What is the difference between DO-35 and DO-41 packages?

A: DO-35 (DO-204AH) is a smaller axial package suitable for compact designs. DO-41 (DO-204AL) is a larger axial package with increased lead diameter and spacing. Substituting DO-35 with DO-41 requires PCB layout modifications including new hole placement and trace routing.

Q: Why do some substitute parts have higher impedance values?

A: Impedance (Zzt) variation reflects internal device characteristics and manufacturing processes across different manufacturers. Higher impedance does not prevent substitution but may affect voltage regulation stability in high-frequency applications. For critical applications, verify impedance specifications against circuit requirements.

Q: Is 1N957B-1 compatible with the original BZX55C6V8 application?

A: Yes. 1N957B-1 provides 6.8 V, 500 mW, ±5% tolerance in DO-35 packaging with -65°C to 175°C operating range. The lower impedance (4.5 Ohms vs. 8 Ohms) and reduced reverse leakage current improve performance characteristics while maintaining electrical compatibility.

Q: Can higher power-rated alternatives (1 W, 1.5 W, 2 W) be used in place of the 500 mW BZX55C6V8?

A: Yes, higher power ratings are electrically compatible and provide thermal margin. However, these alternatives typically use larger packages (DO-41) requiring PCB redesign. Use higher power alternatives only when thermal design benefits justify layout modifications.

Q: What is the impact of tolerance differences (±6% vs. ±5%) on circuit performance?

A: The ±5% tolerance of substitute parts is tighter than the original ±6%, providing improved voltage regulation accuracy. This represents an enhancement rather than a limitation. Both tolerance levels are acceptable for standard voltage regulation applications.

Q: Are all substitute parts suitable for high-temperature applications?

A: No. 2EZ6.8D5-TP has a maximum operating temperature of 150°C, limiting use in high-temperature environments. BZX55C6V8, BZX79C6V8-T50A, and 1N4736A support -65°C to 200°C, making them suitable for extended temperature range applications.

Q: What packaging format should be selected for automated assembly?

A: BZX79C6V8-T50A and 1N5921BP-TP are available in Tape & Reel (TR) packaging, suitable for automated pick-and-place assembly. Bulk packaging alternatives include BZX79C6V8, 1N957B, and 1N957B-1, which require manual handling or custom reel preparation.

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