SLLA628 September 2023 THVD1424
As discussed previously the max bus length, max unterminated stub length, network topology, and emissions concerns are all dependent on data-rate for the device. In general, faster devices mean shorter effective bus length and shorter unterminated stub lengths with a greater concern for EMI. In traditional design different devices would fit into different speed classifications meaning most speeds had a group of parts that serviced it. The THVD1424 on the other hand handles this issue through an integrated selectable slew rate limit option. This is controlled via 1 logic pin that when held low the device can output up to 20Mbps and when held high the devices data rate will be reduced to a maximum of 500Kbps. This allows the THVD1424 to handle faster RS-485 use cases up to 20Mbps – but in length and/or emissions sensitive systems the THVD1424 can also slow its transition times to increase the maximum stub length in a system, effective bus length, and reduce the amount of higher frequency energy generated therefore helping reduce EMI issues.