Method and apparatus for voltage compensation for parasitic impedance

• US 7,242,169 B2
• Filed: 03/01/2005
• Issued: 07/10/2007
• Est. Priority Date: 03/01/2005
• Status: Expired due to Fees

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Kanamori, Takashi, Jauregui, David, Kim, Stephen J.
• Primary Examiner(s): Vu; Bao Q.
• Application Number:
  US11/069,362
• Publication Number:
  US 20060197509A1
• Time in Patent Office: 861 Days
• Field of Search: 323/222, 323/282, 323/284, 323/285, 323/223
• US Class Current: 323/222
• CPC Class Codes: H02M 3/157 with digital control
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

An apparatus and method for regulating a voltage to a load to compensate for one or more parasitic impedances. A first amplifier measures the voltage drop due to a first parasitic impedance, and a second amplifier measures the voltage drop due to a second parasitic impedance. An offset generator sums the first and second voltage drops with a reference voltage, and drives a DC-to-DC converter to produce an input voltage matching the summed voltages. Accordingly, the voltage at a load between the parasitic impedances matches the reference voltage. The load may be, for example, a computer microprocessor or central processing unit.

Claims

1. A voltage regulator, comprising:

a first amplifier comprising;

a first input electrically connected to a first node;

a second input electrically connected to a third node;

a first output;

a second amplifier comprising;

a first input electrically connected to a fourth node;

a second input electrically connected to a second node;

a second output;

an offset generator comprising;

a first input electrically connected to the first output from the first amplifier;

a second input electrically connected to the second output from the second amplifier;

a third input electrically connected to a reference voltage;

an offset output associated with an offset reference voltage and connected to an offset output node;

a compensation amplifier comprising;

a first input electrically connected to the first node; and

a second input electrically connected to the offset output node;

wherein

the compensation amplifier is operative to drive a voltage at the first node to match the offset reference voltage.

2. The voltage regulator of claim 1, further comprising a load electrically connected between the third node and the fourth node, the load chosen from the group comprising:

a central processing unit, a microprocessing unit, and an application-specific integrated circuit.

3. The voltage regulator of claim 1, wherein a voltage between the third node and the fourth node matches the reference voltage.

4. The voltage regulator of claim 3, further comprising:

a DC-to-DC converter, comprising;

a first input electrically connected to a supply voltage;

a second input electrically connected a compensation output of the compensation amplifier;

the DC-to-DC converter operative to produce an input voltage measured between the first and second nodes;

the input voltage varying directly with the offset reference voltage.

5. The voltage regulator of claim 3, the first amplifier comprising:

a first resistor electrically connected between the first node and a first amplifier node;

a second resistor electrically connected between the first amplifier node and a second amplifier node;

a third resistor electrically connected between the third node and a shared amplifier node;

a fourth resistor electrically connected between the second amplifier node and the shared amplifier node; and

a first error amplifier electrically connected to the first amplifier node, the second amplifier node, and a the shared amplifier node.

6. The voltage regulator of claim 5, wherein:

an inverting input of the first error amplifier is connected to the first amplifier node, the inverting input comprising the first input of the first amplifier;

a non-inverting input of the first error amplifier is connected to the shared amplifier node, the non-inverting input comprising the second input of the first amplifier; and

an output of the first error amplifier is connected to the second amplifier node.

7. The voltage regulator of claim 6, wherein the non-inverting input of the first error amplifier draws a first current through the shared amplifier node.

8. The voltage regulator of claim 7, wherein:

the resistances of the first resistor and second resistor are equal; and

the resistances of the third resistor and fourth resistor are equal.

9. The voltage regulator of claim 8, further comprising a first filter capacitor electrically connected between the first node and third node, the first filter capacitor operative to filter a first trace noise.

10. The voltage regulator of claim 8, the second amplifier comprising:

a fifth resistor electrically connected between the fourth node and a fourth amplifier node;

a sixth resistor electrically connected between the fourth amplifier node and a fifth amplifier node;

a seventh resistor electrically connected between the second node and the shared amplifier node;

a eighth resistor electrically connected between the fifth amplifier node and the shared amplifier node; and

a first error amplifier electrically connected to the fourth amplifier node, the fifth amplifier node, and a the shared amplifier node.

11. The voltage regulator of claim 10, wherein:

an inverting input of the second error amplifier is connected to the fourth amplifier node, the inverting input comprising the first input of the second amplifier;

a non-inverting input of the second error amplifier is connected to the shared amplifier node, the non-inverting input comprising the second input of the second amplifier; and

an output of the second error amplifier is connected to the fifth amplifier node.

12. The voltage regulator of claim 11, wherein the non-inverting input of the second error amplifier draws a second current through the shared amplifier node.

13. The voltage regulator of claim 12, wherein:

the resistances of the fifth resistor and sixth resistor are equal; and

the resistances of the seventh resistor and eighth resistor are equal.

14. The voltage regulator of claim 13, further comprising a second filter capacitor electrically connected between the second node and fourth node, the second filter capacitor operative to filter a second trace noise.

15. The voltage regulator of claim 13, the offset generator comprising:

a ninth resistor electrically connected between the shared amplifier node and the offset output node;

a time-constant capacitor electrically connected between the shared amplifier node and the offset output; and

an offset amplifier, comprising;

a first input electrically connected to the shared amplifier node;

a second input electrically connected to a reference voltage; and

an output electrically connected to the offset output node.

16. The voltage regulator of claim 15, wherein:

the offset amplifier'"'"'s first input is an inverting input; and

the offset amplifier'"'"'s second input is a non-inverting input.

17. The voltage regulator of claim 15, wherein:

the first amplifier and second amplifier act as a first and second current sink;

the first current and second current are drawn through the ninth resistor; and

the offset voltage varies with the first current and second current.

18. The voltage regulator of claim 15, wherein the offset amplifier is operative to convert the first current and second current to a voltage.

19. The voltage regulator of claim 18, wherein:

the first current is proportional to a voltage loss from a first impedance electrically connected between the first node and third node; and

the second current is proportional to a voltage loss from a second impedance electrically connected between the second node and fourth node.

20. The voltage regulator of claim 19, wherein the offset voltage equals the sum of the reference voltage, the voltage loss from the first impedance, and the voltage loss from the second impedance.

21. The voltage regulator of claim 20, further comprising:

a load electrically connected between the third node and the fourth node, the load chosen from the group comprising;

a central processing unit, a microprocessing unit, and an application-specific integrated circuit;

wherein

a voltage across the load equals the reference voltage.

22. The voltage regulator of claim 21, wherein:

the first node and second node are external to a die associated with the load;

the third node comprises a first Kelvin sense point associated with the die; and

the fourth node comprises a second Kelvin sense point associated with the die.

23. A method for regulating a voltage, comprising the operations:

measuring a first voltage between a first node and a second node;

measuring a second voltage between a third node and a fourth node;

determining a first voltage loss from a first parasitic impedance between the first node and third node;

determining a second voltage loss from a second parasitic impedance between the second node and fourth node; and

adjusting the first voltage to compensate for the first and second voltage losses.

24. The method of claim 23, further comprising:

determining a reference voltage; and

adjusting the second voltage to match the reference voltage.

25. The method of claim 24, wherein:

the second voltage is measured across a load electrically connected between the third node and fourth node; and

the load is chosen from the group comprising;

a central processing unit, a microprocessing unit, and an application-specific integrated circuit.

26. The method of claim 25, wherein:

the operation of determining a first voltage loss from a first parasitic impedance between the first node and third node comprises generating a current proportional to the first voltage loss; and

the operation of determining a second voltage loss from a second parasitic impedance between the second node and fourth node comprises generating a current proportional to the second voltage loss.

27. The method of claim 26, wherein:

the operation of adjusting the first voltage to compensate for the first and second voltage losses comprises;

generating the first current and second current from a common node; and

generating an offset voltage proportionate to the sum of the first and second currents.

28. The method of claim 27, wherein the operation of generating an offset voltage proportionate to the sum of the first and second currents comprises converting the first and second currents to a voltage by means of an offset amplifier.

29. The method of claim 27, wherein the offset voltage equals the sum of the reference voltage, the first voltage loss, and the second voltage loss.

30. The method of claim 29, further comprising adjusting an input voltage by means of the offset voltage.

31. The method of claim 30, wherein the operation of measuring a first voltage between a first node and a second node comprises:

defining the first node on a computer hardware element as a first hardware sense point;

defining the second node on the computer hardware element as a second hardware sense point; and

measuring the first voltage between the first and second computer hardware sense points.

32. The method of claim 31, wherein the computer hardware element is a motherboard.

33. The method of claim 32, wherein the operation of measuring a second voltage between a third node and a fourth node comprises:

defining the third node as a first Kelvin sense point in a die, the first Kelvin sense point at a first end of the load;

defining the fourth node as a second Kelvin sense point in the die, the second Kelvin sense point at a second end of the load; and

measuring the voltage between the first Kelvin sense point and second Kelvin sense point.