# SwitchCore TX/RX Polarity and Schottky Diode Input Protection

**URL:** <https://forum.botblox.org/t/switchcore-tx-rx-polarity-and-schottky-diode-input-protection/637>\
**Category:** BotBlox Hardware\
**Tags:** switchcore\
**Created:** [August 21, 2026, 4:27pm UTC](https://forum.botblox.org/t/switchcore-tx-rx-polarity-and-schottky-diode-input-protection/637 "2026-08-21T16:27:08Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![ElsieMichaelson](https://avatars.discourse-cdn.com/v4/letter/e/b5ac83/32.png) [@ElsieMichaelson](https://forum.botblox.org/u/ElsieMichaelson)\
**Post date:** [August 21, 2026, 4:27pm UTC](https://forum.botblox.org/t/switchcore-tx-rx-polarity-and-schottky-diode-input-protection/637/1 "2026-08-21T16:27:08Z")

</div>

_This topic was migrated from the BotBlox ticketing system after being summarized and anonymized._

**Question:**  
When designing a custom baseboard for the SwitchCore Module:

1. Can the polarity within an Ethernet pair be swapped, for example RX\_N and RX\_P or TX\_N and TX\_P, to simplify PCB routing?
2. Can a Schottky diode be used at the SwitchCore power input instead of the P-channel MOSFET used on the reference baseboard?

**Answer:**  
The polarity within the Ethernet differential pairs should **not** be swapped. TX+, TX−, RX+, and RX− should be connected according to the SwitchCore baseboard/reference design.

This is separate from Auto-MDIX. Auto-MDIX can handle swapping the transmit and receive **pairs** , but it does not mean the positive and negative signals within an individual differential pair can be reversed. If routing requires the traces to cross, a better approach is to use vias and perform the crossover on another PCB layer.

A **Schottky diode can be used instead of the P-MOSFET** at the power input, provided its forward-voltage drop and current capability are taken into account.

The SwitchCore draws approximately **1.5 W maximum**. At a 5 V input, that corresponds to roughly:

`1.5 W / 5 V = 0.3 A`

With a Schottky forward-voltage drop of up to approximately 0.6 V, the diode would dissipate:

`0.3 A × 0.6 V = 0.18 W`

The voltage delivered to the SwitchCore would also be reduced by the diode’s forward drop. For that reason, using an input voltage of around **6–7 V** is recommended when using a Schottky diode, giving additional margin for the voltage drop.