Embedded universal serial bus 2 repeater
Aspects of the disclosure provide for a circuit including a squelch detector having a first input coupled to a first node and configured to receive a positive component of a differential signal with a floating center tap, a second input coupled to a second node and configured to receive a negative component of the differential signal, and an output coupled to a logic circuit, a first resistor coupled between the first node and a third node, a second resistor coupled between the third node and the second node, a third resistor coupled between the first node and a fourth node, a fourth resistor coupled between the fourth node and the second node, a capacitor coupled between the fourth node and a ground terminal, a comparator having a first input coupled to the third node, a second input coupled to a fifth node, and an output coupled to the logic circuit.
1. A method, comprising:
receiving, at a circuit, data via an idle differential signal line;
performing a squelch detection on the differential signal line;
determining a value of a common mode voltage (Vcm) with reference to a reference voltage (VREF) by performing a comparison; and
verifying a result of the squelch detection with a result of the comparison.
2. The method of claim 1 , wherein VREF has a value greater than an ideal Vcm of high-speed differential communication and less than a value indicative of a logical high value of a single-ended signal.
3. The method of claim 2 , further comprising receiving a skewed single-ended signal pair having rising edge transitions, wherein the result of the squelch detection identifies the skewed single-ended signal pair as high-speed differential communication, and wherein the result of the comparison disproves the result of the squelch detection by indicating that Vcm exceeds VREF.
4. The method of claim 1 , further comprising receiving a differential input signal, wherein the result of the squelch detection identifies the differential input signal as high-speed differential communication, and wherein the result of the comparison verifies the result of the squelch detection by indicating that Vcm is not greater than VREF.