BZX84C39-7 Zener Diode Equivalent & Substitute Parts

Part Overview

The BZX84C39-7 is a 39 V, 300 mW Zener diode manufactured by Diodes Incorporated in SOT-23-3 surface mount packaging. This component is discontinued at DiGi Electronics, necessitating identification of equivalent and substitute parts for ongoing design requirements and production needs. Equivalent parts maintain identical electrical and mechanical specifications, while substitute parts provide functional alternatives within acceptable parameter tolerances for 39 V Zener diode applications.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	39	V
Tolerance	±5%	—
Power - Max	300	mW
Impedance (Max)	130	Ohms
Current - Reverse Leakage @ Vr	100	nA @ 27.3 V
Voltage - Forward (Vf) (Max) @ If	900	mV @ 10 mA
Operating Temperature	-65 to 150	°C
Mounting Type	Surface Mount	—
Package / Case	TO-236-3, SC-59, SOT-23-3	—

Substitute Part Grouping Explanation

Substitution of the BZX84C39-7 is determined by the following critical parameters: nominal Zener voltage (39 V), tolerance specification (±5%), maximum power dissipation capability, impedance characteristics, reverse leakage current, forward voltage drop, operating temperature range, and surface mount SOT-23-3 package compatibility.

Substitute parts are grouped into the following categories:

Category 1: Direct Parametric Equivalents Parts with identical or superior electrical specifications and active product status. These include BZX84C39-7-F (Diodes Incorporated, Tape & Reel packaging, RoHS3 compliant).

Category 2: Manufacturer Alternatives with Reduced Power Rating Parts with 250 mW maximum power (versus 300 mW original specification) but equivalent voltage and tolerance characteristics. These include BZX84-A39,215 (NXP USA Inc., ±1% tolerance, AEC-Q101 automotive qualified), BZX84-C39,215 (Nexperia USA Inc., AEC-Q101 automotive qualified), and BZX84-C39,235 (NXP USA Inc., AEC-Q101 automotive qualified).

Category 3: Reduced Power Rating with Alternative Impedance Parts with 225 mW maximum power and modified impedance specifications. These include BZX84C39LT1G (onsemi, 130 Ohms impedance, AEC-Q101 qualified), SZBZX84C39LT1G (onsemi, 130 Ohms impedance, AEC-Q101 automotive qualified), and SZBZX84C39LT3G (onsemi, 130 Ohms impedance, AEC-Q101 automotive qualified).

Category 4: Increased Power Rating with Alternative Impedance Parts with 225 mW to 350 mW power ratings and 80 Ohms impedance. These include MMBZ5259BLT1G (onsemi, 225 mW, 80 Ohms), CMPZ5259B TR PBFREE (Central Semiconductor Corp, 350 mW, 80 Ohms), and SZMMBZ5259BLT1G (onsemi, 225 mW, 80 Ohms, AEC-Q101 automotive qualified).

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance	Power (mW)	Zzt (Ohms)	Leakage @ Vr (nA)	Vf Max (mV)	Temp Range (°C)	Package	Status	RoHS	AEC-Q101
BZX84C39-7	Diodes Inc.	39	±5%	300	130	100 @ 27.3	900 @ 10mA	-65 to 150	SOT-23-3	Discontinued	Non-compliant	—
BZX84C39-7-F	Diodes Inc.	39	±5%	300	130	100 @ 27.3	900 @ 10mA	-65 to 150	SOT-23-3	Active	RoHS3	—
BZX84-A39,215	NXP USA Inc.	39	±1%	250	130	50 @ 27.3	900 @ 10mA	-65 to 150	SOT-23-3	Active	—	Yes
BZX84-C39,215	Nexperia USA Inc.	39	±5%	250	130	50 @ 27.3	900 @ 10mA	-65 to 150	SOT-23-3	Active	RoHS3	Yes
BZX84-C39,235	NXP USA Inc.	39	±5%	250	130	50 @ 27.3	900 @ 10mA	-65 to 150	SOT-23-3	Active	—	Yes
BZX84C39LT1G	onsemi	39	±5%	225	130	50 @ 27.3	900 @ 10mA	-65 to 150	SOT-23-3	Active	RoHS3	—
SZBZX84C39LT1G	onsemi	39	±5%	225	130	50 @ 27.3	900 @ 10mA	-65 to 150	SOT-23-3	Active	RoHS3	Yes
SZBZX84C39LT3G	onsemi	39	±5%	225	130	50 @ 27.3	900 @ 10mA	-65 to 150	SOT-23-3	Active	RoHS3	Yes
MMBZ5259BLT1G	onsemi	39	±5%	225	80	100 @ 30	900 @ 10mA	-65 to 150	SOT-23-3	Active	RoHS3	—
CMPZ5259B TR PBFREE	Central Semiconductor	39	±5%	350	80	100 @ 30	900 @ 10mA	-65 to 150	SOT-23-3	Active	RoHS3	—
SZMMBZ5259BLT1G	onsemi	39	±5%	225	80	100 @ 30	900 @ 10mA	-65 to 150	SOT-23-3	Active	RoHS3	Yes

Engineering Selection Recommendations

For Direct Replacement (Identical Specifications)

BZX84C39-7-F is the primary direct equivalent, manufactured by Diodes Incorporated with identical electrical parameters (39 V, ±5%, 300 mW, 130 Ohms impedance). This part is active and RoHS3 compliant, providing a seamless substitution for the discontinued BZX84C39-7.

For Automotive and Qualified Applications

Applications requiring AEC-Q101 automotive qualification should select from: SZBZX84C39LT1G, SZBZX84C39LT3G (onsemi, 225 mW, 130 Ohms impedance), BZX84-A39,215 (NXP USA Inc., ±1% tolerance, 250 mW), BZX84-C39,215 (Nexperia USA Inc., 250 mW), BZX84-C39,235 (NXP USA Inc., 250 mW), or SZMMBZ5259BLT1G (onsemi, 225 mW, 80 Ohms impedance). All are active and RoHS3 compliant.

For Reduced Power Dissipation Designs

When maximum power dissipation can be reduced from 300 mW to 225 mW or 250 mW, BZX84C39LT1G (onsemi, 225 mW, 130 Ohms), BZX84-C39,215 (Nexperia, 250 mW, 130 Ohms), or BZX84-C39,235 (NXP, 250 mW, 130 Ohms) are suitable alternatives with maintained impedance characteristics.

For Enhanced Power Capability

CMPZ5259B TR PBFREE (Central Semiconductor Corp, 350 mW, 80 Ohms impedance) provides increased power dissipation capability. This part is suitable for applications requiring higher thermal margin, though impedance differs from the original specification.

For Impedance-Sensitive Applications

Parts maintaining 130 Ohms impedance (matching the original BZX84C39-7) include BZX84C39-7-F, BZX84-A39,215, BZX84-C39,215, BZX84-C39,235, BZX84C39LT1G, SZBZX84C39LT1G, and SZBZX84C39LT3G. Parts with 80 Ohms impedance (MMBZ5259BLT1G, CMPZ5259B TR PBFREE, SZMMBZ5259BLT1G) are suitable only when lower impedance is acceptable for the application.

Frequently Asked Questions (FAQ)

Q: Can BZX84C39-7-F be used as a direct replacement for BZX84C39-7?

A: Yes. BZX84C39-7-F is manufactured by Diodes Incorporated with identical electrical specifications: 39 V nominal Zener voltage, ±5% tolerance, 300 mW maximum power, 130 Ohms impedance, and SOT-23-3 surface mount packaging. The primary difference is packaging format (Tape & Reel versus bulk) and RoHS3 compliance status.

Q: What is the difference between 130 Ohms and 80 Ohms impedance in Zener diodes?

A: Impedance (Zzt) affects the dynamic resistance of the Zener diode during operation. Lower impedance (80 Ohms) results in better voltage regulation under varying load conditions, while higher impedance (130 Ohms) is acceptable for applications with stable load characteristics. Selection depends on circuit requirements for voltage stability.

Q: Are parts with reduced power ratings (225 mW or 250 mW) suitable replacements for the 300 mW original?

A: Reduced power rating parts are suitable only when circuit design confirms that maximum power dissipation will not exceed the substitute part's rating. Thermal analysis of the specific application is required to ensure the lower power rating does not compromise reliability or performance.

Q: What does AEC-Q101 qualification mean?

A: AEC-Q101 is an automotive electronics qualification standard. Parts bearing this qualification have undergone rigorous testing for automotive applications, including temperature cycling, vibration, and reliability assessments. Selection of AEC-Q101 qualified parts is mandatory for automotive and safety-critical applications.

Q: Can I use CMPZ5259B TR PBFREE with its higher 350 mW power rating in place of the 300 mW BZX84C39-7?

A: Yes, from a power dissipation perspective. However, the impedance differs (80 Ohms versus 130 Ohms), which affects voltage regulation characteristics. Circuit validation is required to confirm that the lower impedance does not introduce unacceptable voltage regulation changes in the specific application.

Q: What is the significance of RoHS3 compliance?

A: RoHS3 compliance indicates the part meets Restriction of Hazardous Substances Directive requirements, restricting lead, cadmium, mercury, and other hazardous materials. RoHS3 compliant parts are required for most commercial and consumer applications and are preferred for environmental and regulatory compliance.

Q: Are onsemi SZBZX84C39LT1G and SZBZX84C39LT3G interchangeable?

A: Both parts are manufactured by onsemi with identical electrical specifications (39 V, ±5%, 225 mW, 130 Ohms impedance, AEC-Q101 qualified). The primary difference is packaging format (Cut Tape & Digi-Reel versus Tape & Reel). Selection depends on procurement and assembly requirements.

Q: Which substitute part offers the best overall compatibility with the original BZX84C39-7?

A: BZX84C39-7-F provides the highest compatibility, maintaining all electrical parameters and SOT-23-3 packaging. For applications requiring automotive qualification, SZBZX84C39LT3G or SZBZX84C39LT1G are preferred, with the trade-off of reduced power rating (225 mW versus 300 mW).

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