---
url: /en/docs/xt-c-485-hia-v3_5/schematic/index.md
---
# Schematic

![XT-C-485-HIA-V3/5 schematic (Rev V1.2)](/images/products/xt-c-485-hia-v3_5/XT-C-485-HIA-V3_5-schematic.webp)

Full-board schematic, Rev V1.2. Click to enlarge.

## Blocks

| Block | Contents |
|------|------|
| **Core RS485** | Isolated transceiver `U2`, with decoupling on both sides |
| **VISO Voltage Auto-Select** | Isolated-side supply auto-sensing, which decides whether the isolated-side output level follows a 3.3 V or 5 V system |
| **RS485 Bus Interface & Protection** | Bus protection chain: current-limiting resistors → TVS → gas discharge tube → common-mode choke; includes the 120 Ω termination and the fail-safe bias |
| **Connectors & I/O Protection** | Logic-side `J1` header and bus-side `J3` terminal, plus the input resettable fuse and ESD diodes |
| **Auto-Direction Control & Logic Interface** | Schmitt-trigger shaping and automatic `RE` / `DE` direction switching |

## Cross-checks

* **Logic-side `J1`**: 2.54 mm header, `VIN` / `RX` / `TX` / `GND`
* **Bus-side `J3`**: 5.08 mm terminal, nets `OUT_485+` / `Earth` / `OUT_485-` (pin order is in the [Pinout](./pinout.md))
* **`PE` (Earth) is separate from the logic-side `GND` / `GND1`**: `PE` is only for discharge and shielding; the two do not share ground
* **`J1` / `J3` use SMD & THT pads**: one board can be either surface-mounted or through-hole mounted
* **The 120 Ω termination** is provided by `R5`, connected or disconnected with the `J2` jumper

> Full parameters are in [Specifications](./specs.md); the summary table is on the [product page](/en/products/xt-c-485-hia-v3_5/).