Output voltage compensating circuit and method for a floating gate reference voltage generator

• US 6,894,928 B2
• Filed: 01/28/2003
• Issued: 05/17/2005
• Est. Priority Date: 01/28/2003
• Status: Expired due to Fees

• Current Assignee: Xicor LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Owen, William H.
• Primary Examiner(s): NGUYEN, MATTHEW VAN
• Application Number:
  US10/353,495
• Publication Number:
  US 20040145361A1
• Time in Patent Office: 840 Days
• Field of Search: 323313-316, 365/185.01, 365/185.03, 365/185.05, 365/185.09, 365/185.1, 365/185.14, 365/185.18, 365/185.2, 365/185.21, 36518526-18529
• US Class Current: 365/185.14
• CPC Class Codes: G05F 3/262 using field-effect transistors only

Abstract

An apparatus and method is provided for adjusting a reference voltage at an output terminal of a floating gate reference voltage generator circuit in order to improve the accuracy of the reference voltage at an input terminal of a load circuit. The apparatus and method compensates for the voltage drop produced between the output terminal of the reference voltage generator circuit and the input terminal of the load circuit, and includes a capacitor for capacitively coupling the voltage at the input terminal of said load circuit to a floating gate, and a differential amplifier operatively coupled to the floating gate which acts in response to the capacitively coupled load circuit input voltage to adjust the voltage at the output terminal such that the voltage at the input terminal of the load circuit becomes equal to the reference voltage.

Claims

1. In a system wherein a reference voltage generated by a reference voltage generator circuit is coupled to a load, and wherein said reference voltage generator circuit includes a floating gate that stores a charge that corresponds to said reference voltage, a method for compensating for a voltage drop created in a conductive path between an output terminal of said reference voltage generator circuit and an input terminal of said load, such that the voltage at said output terminal is approximately equal to said reference voltage plus said voltage drop, comprising:

capacitively coupling the voltage at said load input terminal to said floating gate; and

causing said reference voltage generator circuit to act in response thereto to adjust the voltage at said output terminal such that the voltage at said load input terminal becomes approximately equal to said reference voltage.

2. The method of claim 1, wherein said voltage at said output terminal is adjusted by a differential amplifier that includes said floating gate.

3. In a system including a reference voltage generator that includes a floating gate that stores a charge corresponding to a predetermined reference voltage, a method for generating said predetermined reference voltage at an input terminal of a load that is connected to an output terminal of said reference voltage generator by a conductive path, comprising:

capacitively coupling the voltage at said load input terminal to said floating gate; and

causing said reference voltage generator to act in response to the value of said load input terminal voltage to adjust the voltage at said output terminal such that the voltage at said load input terminal becomes approximately equal to said predetermined reference voltage.

4. The method of claim 3, wherein said reference voltage generator includes a differential amplifier having one leg coupled to said floating gate, and wherein the step of causing said reference voltage generator to act in response to said load input terminal voltage includes using said differential amplifier to adjust said reference voltage generator output terminal voltage to a new voltage value that is a function of said predetermined reference voltage and the voltage drop between said output terminal and said load input terminal.

5. The method of claim 3 further comprising the step of charging said floating gate to a predetermined charge corresponding to a predetermined reference voltage.

6. The method of claim 3, wherein the step of adjusting the voltage at said output terminal comprises adjusting said voltage to be equal to the difference between the voltage drop between said output terminal and said load input terminal and said predetermined reference voltage to within a tolerance of plus or minus 10 millivolts.

7. The method of claim 3, wherein the step of capacitively coupling said load input terminal voltage to said floating gate comprises having one of the plates of said capacitor be said floating gate.

8. The method of claim 3 further comprising the step of connecting a current driver between said output terminal and said load input terminal to provide a higher level of current for said load.

9. An apparatus for generating a reference voltage and for coupling said reference voltage to a load, said reference voltage generator compensating for a voltage drop created in a conductive path between the output terminal of said reference voltage generator and an input terminal of said load, said circuit comprising:

a capacitor for capacitively coupling the voltage at said load input terminal to a floating gate; and

a differential amplifier operatively coupled to said floating gate to adjust said voltage at said output terminal in response to said capacitively coupled load input terminal voltage such that the voltage at said load input terminal becomes approximately equal to said reference voltage.

10. The apparatus of claim 9, wherein said capacitor includes two plates, said wherein said floating gate is one of said plates.

11. The apparatus of claim 9, wherein said differential amplifier includes two legs and wherein a first said leg is coupled to said floating gate.

12. The apparatus of claim 11 further comprises a gain stage connected between said differential amplifier and said output terminal.

13. The apparatus of claim 9, wherein said differential amplifier includes two legs, the first said leg coupled to said floating gate and the second said leg coupled to a second floating gate.

14. The apparatus of claim 9 further comprising a current driver connected to said output terminal for providing a higher level of current to said load.

15. The apparatus of claim 9 wherein said voltage drop is generated across a resistive load between said output terminal and said input terminal.

16. The apparatus of claim 15, wherein said resistive load comprises a first resistance between said output terminal and a bonding pad.

17. The apparatus of claim 16, wherein said resistive load further includes a second resistance between said bonding pad and an Integrated Circuit (IC) package pin.

18. The apparatus of claim 17, wherein said resistive load further includes a third resistance between said IC package pin and said input terminal.

19. A floating gate circuit for providing a reference voltage at an input node of a load such that a voltage drop between an output node and said load input node is compensated for, said voltage drop produced in a resistive circuit between said output node and said load input node, said floating gate circuit comprising:

a first floating gate for storing a charge thereon that corresponds to a predetermined reference voltage;

a capacitor having said first floating gate as one plate, said capacitor connected to said load input node; and

a differential amplifier connected to said capacitor, wherein responsive to the voltage at said load input node, said differential amplifier adjusts the voltage at said output node such that the voltage at said load input node becomes approximately equal to said reference voltage.

20. The floating gate circuit of claim 19, wherein said output node comprises an IC bonding pad.

21. The floating gate circuit of claim 20, wherein said load input node comprises an IC package pin.