BZX84B39-7-F Equivalent & Substitute Parts

Part Overview

The BZX84B39-7-F is a 39 V Zener diode manufactured by Diodes Incorporated, rated for 350 mW maximum power dissipation in a surface mount SOT-23-3 package. This component is classified as Active product status and is ROHS3 compliant. Substitute parts are identified when equivalent electrical performance and mechanical compatibility are required due to inventory constraints, supply chain considerations, or design flexibility needs while maintaining functional equivalence within specified tolerance ranges.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nominal)	39	V
Power - Maximum	350	mW
Tolerance	±2%	—
Package / Case	SOT-23-3 (TO-236-3, SC-59)	—
Mounting Type	Surface Mount	—
Operating Temperature Range	-65 to 150	°C
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the BZX84B39-7-F is permissible when the following electrical and mechanical parameters align with application requirements:

Critical Matching Parameters:

Zener voltage nominal value: 39 V
Package type: SOT-23-3 surface mount configuration
Operating temperature range: -65°C to 150°C minimum
RoHS3 compliance status
Mounting type: Surface Mount

Allowable Variation Parameters:

Voltage tolerance: ±2% to ±5% (wider tolerance acceptable for non-precision applications)
Power rating: 225 mW to 350 mW (lower power rating acceptable if application current requirements are met)
Impedance (Zzt): 80 to 130 Ohms (within specified range)
Reverse leakage current: 50 to 100 nA (within specified range)

The identified substitute parts CMPZ5259B TR PBFREE and SZBZX84C39ET1G maintain the core 39 V zener voltage specification and SOT-23-3 package compatibility while operating within the same temperature envelope.

Parameter Comparison

Parameter	BZX84B39-7-F (Main)	CMPZ5259B TR PBFREE (Substitute)	SZBZX84C39ET1G (Substitute)
Manufacturer	Diodes Incorporated	Central Semiconductor Corp	onsemi
Voltage - Zener (Nom)	39 V	39 V	39 V
Tolerance	±2%	±5%	±5%
Power - Max	350 mW	350 mW	225 mW
Impedance (Max)	130 Ohms	80 Ohms	130 Ohms
Current - Reverse Leakage @ Vr	100 nA @ 27.3 V	100 nA @ 30 V	50 nA @ 27.3 V
Voltage - Forward (Vf) (Max) @ If	900 mV @ 10 mA	900 mV @ 10 mA	900 mV @ 10 mA
Operating Temperature	-65°C ~ 150°C	-65°C ~ 150°C	-65°C ~ 150°C
Package / Case	SOT-23-3	SOT-23-3	SOT-23-3
Mounting Type	Surface Mount	Surface Mount	Surface Mount
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
MSL	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)
REACH Status	REACH Unaffected	REACH Unaffected	REACH Unaffected

Engineering Selection Recommendations

CMPZ5259B TR PBFREE (Central Semiconductor Corp)

This substitute maintains full electrical equivalence at the 39 V zener voltage specification with identical 350 mW power rating. The ±5% tolerance is wider than the main part's ±2%, suitable for applications where voltage regulation precision is not critical. The lower impedance value (80 Ohms versus 130 Ohms) provides improved dynamic response characteristics. All compliance certifications (ROHS3, REACH Unaffected) and operating temperature range (-65°C to 150°C) are maintained. This part is appropriate for direct substitution in non-precision voltage regulation circuits.

SZBZX84C39ET1G (onsemi)

This substitute provides the 39 V zener voltage specification with AEC-Q101 automotive qualification and Automotive grade designation. The power rating is reduced to 225 mW, which limits application to circuits with lower current requirements. The impedance specification matches the main part (130 Ohms). Reverse leakage current is improved at 50 nA. All compliance certifications and operating temperature range are maintained. This part is appropriate for automotive applications or where enhanced reliability qualification is required, provided the 225 mW power limit is acceptable.

Frequently Asked Questions (FAQ)

Q: Can CMPZ5259B TR PBFREE be used as a direct replacement for BZX84B39-7-F?

A: Yes, for applications where the ±5% voltage tolerance is acceptable. Both parts share the 39 V nominal zener voltage, 350 mW power rating, SOT-23-3 package, and -65°C to 150°C operating temperature range. The lower impedance (80 Ohms) of the CMPZ5259B may improve transient response in some circuits.

Q: What is the primary limitation of SZBZX84C39ET1G as a substitute?

A: The maximum power rating is 225 mW compared to 350 mW for the main part. This substitute is suitable only for applications where the circuit current requirements do not exceed the 225 mW dissipation limit. The automotive qualification (AEC-Q101) makes this part preferable for automotive applications within this power constraint.

Q: Are all three parts compatible with the same PCB footprint?

A: Yes. All three parts use the SOT-23-3 (TO-236-3, SC-59) package, which provides identical mechanical and electrical pin compatibility for surface mount assembly.

Q: Does tolerance difference affect circuit performance?

A: The BZX84B39-7-F specifies ±2% tolerance while both substitutes specify ±5%. In precision voltage regulation applications, the tighter tolerance of the main part may be required. For general-purpose voltage clamping or protection circuits, the ±5% tolerance of the substitutes is typically acceptable.

Q: Are there compliance or regulatory differences between these parts?

A: All three parts are ROHS3 compliant and REACH Unaffected. The SZBZX84C39ET1G carries additional AEC-Q101 automotive qualification, making it suitable for automotive applications where this certification is required.

Q: What is the impedance difference and does it matter?

A: The CMPZ5259B has 80 Ohms maximum impedance while the BZX84B39-7-F and SZBZX84C39ET1G both specify 130 Ohms. Lower impedance provides better transient response and faster voltage regulation. For applications sensitive to transient overshoot, the CMPZ5259B may provide superior performance.

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