DC-DC converters having improved current sensing and related methods

1. An integrated circuit configured to be coupled to a current sensing element and a set resistor having a resistance R set , the integrated circuit comprising:

a sense resistor having a resistance R sense , the sense resistor coupled to an input of the integrated circuit such that a first sensed current from the current sensing element flows through the sense resistor;

a reference resistor having a resistance R reference which is a fixed multiple of R sense ; and

circuitry configured to produce an output current such that the value of the output current is proportional to a value of R set and a fixed ratio between R sense and R reference .

2. The integrated circuit of claim 1 , wherein the circuitry in the integrated circuit includes tracking circuitry configured to drive the reference resistor such that a voltage across the reference resistor is substantially equal to a voltage across the set resistor.

3. The integrated circuit of claim 2 , wherein the tracking circuitry comprises:

a source follower coupled to a low potential side of the reference resistor; and

an operational amplifier having an output coupled to a gate of the source follower.

4. The integrated circuit of claim 1 , wherein the reference resistor and the sense resistor are comprised of the same type of material.

5. The integrated circuit of claim 1 , wherein the circuitry in the integrated circuit is configured to determine a ratio of current through R set to current through R reference and to combine the ratio of current through R set to current through R reference with a first measurement current to produce the output current.

6. An integrated circuit comprising:

a first input configured to be coupled to a current sensing element;

a second input configured to be coupled to a set resistor having a first resistance;

a sense resistor having a second resistance, the sense resistor coupled to the first input such that a voltage is placed across the sense resistor to generate a first measurement current based on the second resistance;

a reference resistor having a third resistance, the third resistance being a fixed multiple of the second resistance; and

a current multiplier configured to generate a second measurement current which is indicative of a load current and is independent of the second resistance by combining the first measurement current with a ratio of current at the second input to current through the reference resistor.

7. The integrated circuit of claim 6 , further comprising tracking circuitry configured to drive the reference resistor such that a voltage across the reference resistor is substantially equal to a voltage across the set resistor.

8. The integrated circuit of claim 7 , wherein the tracking circuitry comprises:

a source follower coupled to a low potential side of the reference resistor; and

an operational amplifier having an output coupled to a gate of the source follower.

9. The integrated circuit of claim 6 , wherein the reference resistor and the sense resistor are comprised of the same type of material.

10. The integrated circuit of claim 6 , further comprising:

a transistor having a gate, a source and a drain; and

an operational amplifier having an input coupled to the sense resistor and an output coupled to the gate of the transistor;

wherein the drain of the transistor is coupled to the current multiplier to provide the first measurement current to the current multiplier.