Calibration of single-ended high-speed interfaces
View Patent ↗A method for calibrating signal swing and a trip reference voltage. The signal swing of a system can be calibrated in a symmetric or asymmetric technique through adjustment of a drive parameter such as a supply voltage for a transmitter or a drive termination. The trip reference voltage of the system can also be calibrated in a symmetric or asymmetric technique through sampling of a data pattern to determine an ideal level of the trip reference voltage.
1. A method for calibrating signal swing of a transmitting device connected to a receiving device via a connection, a drive parameter of the transmitting device affecting an output voltage on the connection, the method comprising:
prior to engaging a receiver termination of the receiving device:
engaging an external precision resistor at a calibration channel of the transmitting device,
obtaining a preliminary value of the drive parameter based on comparing and adjusting a voltage drop across the external precision resistor at the calibration channel with reference to a calibration reference voltage, and
preadjusting the drive parameter to the preliminary value;
engaging the receiver termination of the receiving device, the receiver termination coupled to the connection;
driving, at the transmitting device, the connection to produce the output voltage level on the connection while the receiver termination is engaged;
comparing, at the transmitting device, the output voltage level to a reference voltage level corresponding to a threshold voltage swing; and
adjusting, at the transmitting device, the drive parameter from the preliminary value based on a result of comparing the output voltage level to the reference voltage level.
2. The method of claim 1 , wherein the drive parameter is adjusted until the output voltage level reaches the reference voltage level.
3. The method of claim 1 , wherein the transmitting device drives the connection with a supply voltage using a drive termination, and the transmitting device adjusts the drive parameter affecting the output voltage by adjusting the drive termination.
4. The method of claim 3 , further comprising:
generating, at the transmitting device, the reference voltage level based on an ideal value of the drive termination, an ideal value of the receiver termination, and ideal level of the supply voltage.
5. The method of claim 1 , wherein the transmitting device drives the connection with a supply voltage using a drive termination, and the transmitting device adjusts the drive parameter affecting the output voltage by adjusting a level of the supply voltage.
6. The method of claim 1 , wherein the connection is a single-ended connection.
7. The method of claim 1 , wherein the reference voltage level is generated by a resistor divider.
8. The method of claim 7 , wherein the resistor divider is a matched resistor divider.
9. The method of claim 1 , wherein engaging the receiver termination comprises turning on a switch for the receiver termination.
10. A system comprising:
a receiving device having a receiver termination coupled to a connection and that is selectively engaged; and
a transmitting device coupled to the receiving device via the connection, a drive parameter of the transmitting device affecting an output voltage level on the connection, wherein prior to engaging the receiver termination of the receiving device, the transmitting device engages an external precision resistor at a calibration channel of the transmitting device, obtains a preliminary value of the drive parameter based on comparing and adjusts a voltage drop across the external precision resistor at the calibration channel with reference to a calibration reference voltage, and preadjusts the drive parameter to the preliminary value, and wherein the transmitting device comprises:
a transmitter interface coupled to the connection to the receiving device, the transmitter interface driving the connection to produce the output voltage level on the connection while the receiver termination is engaged; and
a comparator to compare the output voltage level to a reference voltage level corresponding to a threshold voltage swing, the transmitting device adjusting the drive parameter from the preliminary value based on an output of the comparator.
11. The transmitting device of claim 10 , wherein the drive parameter affecting the output voltage level is adjusted until the output voltage level reaches the reference voltage level.
12. The transmitting device of claim 10 , wherein the transmitting device drives the connection with a supply voltage using a drive termination, and the transmitting device adjusts the parameter affecting the output voltage level by adjusting the drive termination.
13. The transmitting device of claim 12 , wherein the transmitting device generates the reference voltage level based on an ideal value of the drive termination, an ideal value of the receiver termination, and ideal level of the supply voltage.
14. The transmitting device of claim 10 , wherein the transmitting device drives the connection with a supply voltage using a drive termination, and the transmitting device adjusts the parameter affecting the output voltage level by adjusting a level of the supply voltage.
15. The transmitting device of claim 10 , wherein the connection is a single-ended connection.