BAT54 Schottky Diode Series: SOT-23 Cross-Reference and Pinout Guide

BAT54 is one of those diode names that looks simple on a BOM but can cause confusion during replacement.

The reason is easy to see.BAT54, BAT54A, BAT54C and BAT54Scan all use a SOT-23 package, but they do not have the same internal connection.

That matters much more than the package outline.

Diodes Incorporated defines the BAT54 family as 30V, 200mA Schottky barrier diodes in the standard SOT23 package. The family includes single, common-anode, common-cathode and series configurations.

So when a buyer asks for aBAT54 replacement, my first question is not "which brand?" It is:

Which BAT54 configuration is actually on the PCB?

BAT54, BAT54A, BAT54C and BAT54S Are Not the Same Connection

The suffix matters.

In the Diodes Incorporated BAT54 family:

· BAT54= single diode

· BAT54A= dual diode, common anode

· BAT54C= dual diode, common cathode

· BAT54S= dual diode, series connection

The same SOT-23 package can therefore contain different internal diode arrangements.

This is where many simple cross-reference searches go wrong.

A SOT-23 footprint can physically accept a replacement, but the circuit will not work if the internal connection is different.

For example, replacingBAT54Cwith a common-anode version is not a drop-in substitution. The package may look identical from the outside, but the two diodes are connected differently inside.

For procurement, I would always include the suffix when searching for a replacement.

What Makes a BAT54 a Schottky Diode?

The BAT54 family is designed around low forward voltage and fast switching.

Diodes Incorporated lists a 30V reverse voltage rating and 200mA forward current for its standard BAT54 family. Its product data also lists fast switching behavior and a typical forward-voltage figure around 0.32V at 1mA.

That low forward drop is one reason these small Schottky diodes appear in:

· Signal steering

· Clamping

· Rectification

· Switching circuits

· Interface protection

· Small power rails

But "low VF" should not be treated as a fixed number.

Forward voltage changes with forward current, temperature and the exact manufacturer's specification. The value at 1mA is not the same as the value at 100mA.

That is an important point when comparing aSOT-23 Schottky diodefrom different manufacturers.

BAT54A vs BAT54C: Which One Should Be Used?

The answer comes from the circuit, not the diode's headline electrical specifications.

Diodes Incorporated lists both BAT54A and BAT54C at 30V and 200mA, with the difference being the internal configuration. BAT54A is common-anode, while BAT54C is common-cathode.

So the question is not:

"Which one has the lower forward voltage?"

The useful question is:

"Where are the two cathodes and anodes connected in the original circuit?"

That is how I would check aBAT54C vs BAT54A differencebefore approving a substitute.

What Is Special About BAT54S?

BAT54Scontains two Schottky diodes connected in series. Diodes Incorporated specifies the device as a dual series configuration in SOT-23, with a 30V reverse-voltage rating and 200mA forward-current rating.

Because the two diodes are internally connected, BAT54S cannot simply replace a BAT54, BAT54A or BAT54C without checking the circuit.

This is particularly important for anyone searching for aBAT54S pin to pin alternative.

The replacement needs the same internal topology, not just:

· SOT-23 package

· 30V rating

· 200mA current rating

Those three numbers are not enough.

What About ROHM and Panasonic?

There is another detail worth knowing when doing a manufacturer cross-reference.

ROHM currently offers parts such asBAT54AHY, BAT54CHY and BAT54SHYin SOT-23, with 30V reverse voltage and 200mA average rectified forward current. ROHM identifies BAT54AHY as common-anode, BAT54CHY as common-cathode, and BAT54SHY as a series-connected device.

These are useful references when looking for aROHM to Diodes Inc BAT54 replacement, but the complete ordering code and pinout should still be checked.

Panasonic requires a little more care. Panasonic has supplied similar small Schottky diodes, but it does not mean every Panasonic Schottky should be treated as a BAT54-series equivalent. Some older Panasonic discrete diode products have also been discontinued or transferred as part of its discrete semiconductor business changes.

For that reason, I would not put a generic "Panasonic BAT54" into a BOM without confirming the exact Panasonic MPN.

Can BAT54 Diodes Be Used for ESD Protection?

They can be used for certain low-level protection and clamping functions, but a BAT54 should not automatically be treated as a dedicated ESD protection IC.

Diodes Incorporated does note transient and ESD protection as an application feature for its BAT54 product.

Still, the actual suitability depends on the line voltage, transient waveform, clamping target, leakage requirement and capacitance.

For a high-speed data interface or a product with formal IEC ESD requirements, I would normally compare the BAT54 with a dedicated ESD protection device rather than assuming they are interchangeable.

What I Check Before Approving a BAT54 Replacement

For an actualSOT-23 Schottky diode cross reference, I normally check five things:

1. Internal configuration- single, common-anode, common-cathode or series.

2. Pinout- confirm the actual SOT-23 pin assignment.

3. VRRM/VR- make sure the reverse-voltage rating is sufficient.

4. IF and VF- compare the forward-current requirement and VF at the actual operating current.

5. Leakage and capacitance- especially important in signal and clamp circuits.

Package matching comes after those checks.

The BAT54 family is inexpensive and widely used, but that does not make every BAT54 marking interchangeable. When replacing one, the suffix and internal connection are often more important than the brand name.

For sourcing teams, this is also why an exactBAT54S replacementorBAT54 diode replacementshould always be checked by complete MPN and datasheet rather than by "BAT54" as a general search term.If you need help verifying your BOM or finding stock, feel free to request a fast quote and cross-reference analysis from XMAGELEC.