Is there a pin-compatible replacement for MMSZ5250B?

No verified pin-to-pin replacement is available. Candidates like MMSZ5248B and BZT52C18 share the same SOD-123 package and are likely pin-compatible, but their Zener voltage differs from the original 20V.

What risks should I check before replacing MMSZ5250B?

The main risk is the difference in Zener voltage (Vz). Using an 18V or 24V diode instead of 20V will change the regulation point of your circuit. Always verify this change is acceptable for your application.

MMSZ5250B Alternatives, Datasheet & Cross Reference | onsemi

MMSZ5250B is an obsolete 20V, 500mW Zener diode in a SOD-123 package. While no direct drop-in replacement is available, several parametric alternatives with different Zener voltages exist that may be suitable after engineering review.

AI replacement insight

Electrical riskmedium

Candidate Zener voltage differs from the 20V target, which will change circuit behavior.

Package risklow

All suggested alternatives use the same SOD-123 package.

Can it be replaced directly?

No, there is no direct, drop-in replacement for the MMSZ5250B. All viable alternatives require review due to different Zener voltages.

Best replacement path

Select a parametric alternative like MMSZ5248B (18V) or BZT52C24 (24V) based on whether your circuit can tolerate a lower or higher regulation voltage.

Main risk

The primary risk is functional failure or circuit damage due to the incorrect voltage regulation point.

Recommended alternatives

A cross-vendor alternative in the same package and power rating, but with a lower Zener voltage of 18V.

View details

Alternative comparison matrix

Feature / factor	MMSZ5250B	BZT52C18	MMSZ5248B	BZT52C24	Compatibility / risk
Package	SOD-123	SOD-123	-	-	SOD-123 — Same package ensures form-fit compatibility.
Voltage	20V	18V	-	-	24V — Higher Zener voltage. Will regulate at 24V instead of 20V. Must be verified.
Power	500mW	500mW	-	-	500mW — Same power rating.
Manufacturer	Fairchild Semiconductor	-	Fairchild Semiconductor	-	Fairchild Semiconductor — Same original manufacturer.
Pinout	2 pins	-	-	Missing	Missing — Pin count data missing, but SOD-123 is a standard 2-pin package.

Application & sourcing insights

Questions & answers

The best alternative depends on your circuit's voltage tolerance. MMSZ5248B (18V) and BZT52C24 (24V) are strong candidates in the same package and power rating, but require review of the voltage difference.