This topic was migrated from the BotBlox ticketing system after being summarized and anonymized.
Question
We are building a custom carrier board based on a BotBlox reference design, but our manufacturer does not want to source some of the specified components from LCSC.
The affected parts include the Ethernet pulse transformer and common-mode choke. Equivalent parts appear to be available from distributors such as DigiKey and Mouser.
Is LCSC the only source for these components, or can alternative transformer and common-mode choke parts be used?
Answer
LCSC is not the only option. There are many compatible Ethernet transformers and common-mode chokes available from DigiKey, Mouser and other established distributors.
The exact components in the reference design are not mandatory. The most important requirement is that both replacement parts support 1000BASE-T Gigabit Ethernet.
BotBlox sometimes purchases parts through LCSC because we can audit the components received at our production volumes. For prototypes and smaller production runs, sourcing through DigiKey or Mouser is often more practical, even if the components are slightly more expensive.
What should be checked before substituting the parts?
A replacement should not be selected only because it is described as an Ethernet transformer or common-mode choke. Confirm that it is suitable for 1000BASE-T and compatible with the original circuit.
Ethernet transformer
Check the replacement part’s:
- 1000BASE-T compatibility
- Number of channels
- Pinout and center-tap arrangement
- Turns ratio
- Isolation-voltage rating
- Insertion-loss and return-loss performance
- PCB footprint and package dimensions
- Operating-temperature range
Common-mode choke
Check the replacement part’s:
- 1000BASE-T compatibility
- Number of channels and line pairs
- Common-mode impedance
- Differential insertion loss
- Current and voltage ratings
- Pinout and PCB footprint
- Operating-temperature range
The transformer and common-mode choke should also be validated as a compatible pair. Component manufacturers often publish recommended combinations for specific Ethernet standards.
Can the alternative parts be drop-in replacements?
They can be drop-in replacements if their electrical characteristics, pinout and footprint match the original components.
If the footprint or pin arrangement differs, the alternative may still be electrically suitable, but the PCB layout will need to be modified. Particular attention should be paid to the Ethernet differential pairs so that the revised layout preserves the intended 100 Ω differential impedance and does not introduce unnecessary stubs or routing discontinuities.
What is the recommended sourcing approach?
For prototypes and low-volume production:
- Search DigiKey, Mouser or another authorized distributor for parts explicitly rated for 1000BASE-T.
- Compare the candidate datasheets against the original components.
- Confirm the footprint, pinout and electrical specifications.
- Verify that the transformer and common-mode choke are intended to work together.
- Review any substitutions with the PCB manufacturer before assembly.
- Test the completed hardware across every required link speed, cable length and environmental condition.
The key point is: the reference-design components can be substituted, provided both replacements support 1000BASE-T and are electrically and mechanically compatible with the design.