Transmitter Module Stepwise Resistor Control for Bus Signal Emissions

The transition process is segmented into multiple discrete steps using a delay chain. Instead of a single abrupt transition, the common-mode level is adjusted in successive stages through multiple switching events, each separated by a delay period. This segmentation reduces the spectral density of electromagnetic emissions by distributing the transition energy across time.

The common-mode level is adjusted in advance before the differential signal transition occurs. The control logic first switches the common-mode resistors to the target resistance value, waits for the delay chain to expire, and then switches the differential signal. This preliminary adjustment of the common-mode level prevents simultaneous switching of differential and common-mode signals, reducing electromagnetic interference.

A single delay chain is designed to serve multiple purposes: it controls the timing of common-mode resistor switching, generates intermediate transition states, and coordinates the overall transition sequence. This universal delay chain replaces what would otherwise require multiple specialized analog time step generators, significantly reducing circuit complexity while maintaining the ability to generate optimized error-function-like transition shapes.

The transition characteristics are controlled by changing the resistance values in the delay chain rather than using complex analog circuitry. By adjusting the resistance parameters in the delay chain, the transition shape can be optimized to approximate the error function without requiring multiple specialized generators. This parameter-based control simplifies the circuit while achieving the desired transition optimization.

Multiple chains that would traditionally be required to generate five different static states are merged into a single delay chain structure. The single delay chain, combined with the full-bridge resistor network, can generate all five CAN XL signal states (REC, SIC, DOM, LV0, LV1) by controlling the switching sequence and timing. This merging reduces the circuit area and power consumption while maintaining full signal state coverage.

The system uses dynamic switching control to generate multiple static states from a single configurable structure. The delay chain can be programmed with different delay values to dynamically adapt to different signal state transitions, eliminating the need for multiple dedicated chains for each state. This dynamic approach allows the same hardware to serve multiple functions across different operating modes.