Programmable termination resistor for HDMI transmitter output
AssigneePICO Semiconductor, Inc.
InventorKamran Iravani
Life of this patent
Estimating the term…
Abstract
A supply-less transmitter output termination resistor with high accuracy is presented. This termination resistor can be used for applications with high supply voltage and low voltage devices. The termination resistor is programmable and includes many parallel branches. Each branch can be turned off or on with a switch. The biasing for the switch is in such a way that it keeps the resistance of the switch constant independent of the supply voltage or the output common mode voltage. This will increase the accuracy of the termination resistor. Besides HDMI this technique can be used for many other applications.
Claims20
A termination resistor circuit, comprising:
- a branch comprising a first branch resistor and a second branch resistor;
- a transistor is coupled between the first branch resistor and the second branch resistor;
- a biasing circuit is coupled to a first node between the transistor and the first branch resistor and is coupled to a second node between the transistor and the second branch resistor, the biasing circuit further comprises:
- a first load resistor coupled to the first node and a second load resistor coupled to the second node;
- a switch coupled to the first load resistor and second load resistor;
- and
- a current source coupled to the first load resistor and second load resistor via the switch, wherein when the switch is on, the average current flowing through each of first and second load resistors is half of the current of the current source to bias the transistor.
A termination resistor circuit, comprising:
- a branch comprising a first branch resistor and a second branch resistor;
- a transistor is coupled between the first branch resistor and the second branch resistor;
- a biasing circuit is coupled to a first node between the transistor and the first branch resistor and is coupled to a second node between the transistor and the second branch resistor, the biasing circuit further comprises:
- a first load resistor coupled to the first node and a second load resistor coupled to the second node;
- a switch coupled to the first load resistor and second load resistor;
- and
- a current source coupled to the first load resistor and second load resistor via the switch, wherein when the switch is on, the average current flowing through each of first and second load resistors is half of the current of the current source to bias the transistor;
- and
- a protection transistor coupled between the first and second load resistors and the switch and current source to protect the switch and the current source from stress.
A termination resistor circuit, comprising:
- a branch comprising a first branch resistor and a second branch resistor;
- a transistor is coupled between the first branch resistor and the second branch resistor;
- a biasing circuit is coupled to a first node between the transistor and the first branch resistor and is coupled to a second node between the transistor and the second branch resistor, the biasing circuit further comprises:
- a first load resistor coupled to the first node and a second load resistor coupled to the second node;
- a switch coupled to the first load resistor and second load resistor;
- and
- a current source coupled to the first load resistor and second load resistor via the switch, wherein when the switch is on, the average current flowing through each of first and second load resistors is half of the current of the current source to bias the transistor, wherein the current of the current source is proportional to Vbg/R where Vbg is a constant voltage generated by a bandgap circuit, causing the voltage across first and second load resistors to be constant regardless of what the output common mode voltage Vcm is, such that the rds of the transistor will not change when Vcm changes.
Dependencies are inferred from the claim text.