Interface Circuit Switching to Suppress Common-Mode Discharge Noise
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Solution Overview
Problem
Conventional interface circuits generate channel noises due to instantaneous discharge of the common mode capacitor, leading to potential misinterpretation of receiver signals.
Innovation Solution
An interface circuit design that includes a receiver, first and second terminal resistors, a switch circuit, and a switch control circuit, where the switch control circuit controls the switch circuit to discharge the common mode capacitor before coupling with the terminal resistors, thereby suppressing channel noises by managing the switch control signals based on channel voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the terminal resistors are coupled to the common mode capacitor, then the receiver can operate in high-speed differential mode, but channel noises are generated due to instantaneous discharge
Solution Approach 1:
The patent applies preliminary action by discharging the common mode capacitor through a discharge switch before coupling the terminal resistors to the capacitor. This preliminary discharge action eliminates the voltage across the capacitor in advance, so when the terminal resistors are subsequently coupled to the capacitor, no instantaneous discharge occurs and channel noises are prevented. The discharge switch is controlled to activate before the coupling switches, ensuring the capacitor is ready for coupling without generating harmful noises.
2Object-generated harmful factors
If the common mode capacitor is discharged before coupling, then channel noises are suppressed, but additional control circuitry is required
Solution Approach 1:
The patent implements periodic action through a control signal that periodically activates the discharge switch at appropriate intervals before each coupling operation. The control circuit generates timed control signals that rhythmically switch the discharge path on and off, ensuring the capacitor is discharged at the right moment before coupling while maintaining simplicity. This periodic control approach manages the discharge-coupling sequence efficiently without requiring complex continuous control mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively suppresses channel noises, preventing misinterpretation of receiver signals by discharging the common mode capacitor before coupling with terminal resistors, ensuring signal integrity in high-speed differential signal modes.
Implementation Method 1
a common mode capacitor Ccom, a terminal resistor R1, a terminal resistor R2, a switch SW1 and a switch SW2. The switches SW1 and SW2 are respectively controlled by switch control signals SSW1 and SSW2 to couple the terminal resistors R1 and R2 to the common mode capacitor Ccom.
Implementation Method 2
At the instant when the switches SW1 and SW2 are turned on, noises ΔV1 and ΔV2 are produced at the channels ch1 and ch2 due to instantaneous discharge of the common mode capacitor Ccom.
Data Source
AI summary
An interface circuit includes a receiver, a first terminal resistor, a second terminal resistor, a switch circuit and a switch control circuit. The receiver has a first channel and a second channel. The first channel receives a first channel voltage, and the second channel receives a second channel voltage. According to the first channel voltage and the second channel voltage, the switch control circuit controls the switch circuit to discharge a common mode capacitor before the first terminal resistor or the second terminal resistor couple to the common mode capacitor.