Dual-Mode Squelch Detectors for USB High-Speed Handshake Reliability

The squelch detector dynamically switches between two operational modes (first mode for full-speed communication, second mode for high-speed communication) based on the detected communication speed. This dynamic adaptation allows the detector to adjust its threshold voltage levels accordingly, resolving the contradiction between detection reliability and device complexity by making the detection mechanism flexible rather than fixed.

The patent changes the threshold voltage level parameter of the squelch detector based on the communication mode. In the first mode (full-speed), the detector uses a first threshold voltage level, while in the second mode (high-speed), it uses a second threshold voltage level. This parameter change enables accurate line state detection across different communication speeds, improving reliability without requiring an overly complex fixed-threshold design.

The dual-mode squelch detector dynamically adapts its threshold voltage levels based on the communication speed being negotiated. During high-speed detection handshaking, the detector operates in the second mode with adjusted threshold levels that account for offset voltages, ensuring reliable line state detection. This dynamic adaptation maintains both versatility (supporting multiple communication modes) and reliability (successful handshakes) simultaneously.

The squelch detector continuously monitors the differential signal and compares it against the appropriate threshold voltage level based on the current communication mode. This feedback mechanism ensures that the detector correctly identifies line states during high-speed handshaking, preventing aborts and ensuring successful communication mode negotiation while maintaining backward compatibility.