Precision reference current generator

• US 5,291,123 A
• Filed: 09/09/1992
• Issued: 03/01/1994
• Est. Priority Date: 09/09/1992
• Status: Expired due to Term

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Brown, Charles A.
• Primary Examiner(s): STERRETT, JEFFREY L
• Application Number:
  US07/944,852
• Time in Patent Office: 538 Days
• Field of Search: 323/312, 323/364, 323/367, 323/369
• US Class Current: 323/369
• CPC Class Codes: G05F 3/24 wherein the transistors are of the field-effect type only G05F3/205, G05F3/26, G05F3/30 take precedence

Abstract

An integrated current generator circuit operates in conjunction with a known reference voltage and internal and external reference resistances. The current generator circuit includes three operational modes. In the first operational mode, the reference voltage is impressed upon the internal reference resistance to generate one or more relatively inaccurate output currents. In a second operational mode, the reference voltage is impressed upon an external reference resistance to generate one or more highly accurate output currents, even if an internal ESD resistor is used, or if the bonding pad has high series parasitic resistance. An alternative voltage sensing path is included to ensure the accuracy of the reference current. In a third operational mode, the reference voltage is again impressed upon the internal resistance, with the corresponding node voltage being connected to an external integrated circuit bonding pad.

Claims

1. A resistance circuit block for use in an integrated circuit reference current generator comprising:

a current node through which a current from a voltage-controlled current source is supplied;

a voltage sensing node for supplying voltage feedback to the voltage-controlled current source;

an external bonding pad for coupling to an external current-setting resistor;

a first electrostatic protection resistor coupled between the current node and the external bonding pad; and

a second electrostatic protection resistor coupled between the voltage sensing node and the external bonding pad.

2. A resistance circuit block according to claim 1 further comprising switch means for coupling the current node and the voltage sensing node to an internal resistor in a first operational mode and for coupling the current node and the voltage sensing node to the external bonding pad through the first and second protection resistors, respectively, in a second operational mode.

3. A resistance circuit block according to claim 2 in which the switch means comprises:

a first switch coupled between the current node and the internal resistor;

a second switch coupled between the current node and a first end of the first electrostatic resistor not coupled to the bond pad;

a third switch coupled between the voltage sensing node and a first end of the second electrostatic protection resistor not coupled to the bond pad; and

a fourth switch coupled between the voltage sensing node and the internal current-setting resistor.

4. A resistance circuit block according to claim 3 in which the switch means further comprises means for coupling the voltage on the internal resistor to the external bonding pad in a third operational mode.

5. A resistance block according to claim 4 in which the coupling means comprises a fifth switch coupled between the internal current-setting resistor and a first end of the first electrostatic resistor not coupled to the bond pad.

6. A resistance bock according to claim 4 in which the switch means further comprises control means for receiving first and second control signals for placing the resistance blocks in one of the first, second, and third control modes.

7. A method for generating a precision current in an integrated circuit having first and second electrostatic resistors coupled to a bond pad, the method comprising the steps of:

coupling a precision current-setting resistor to the bond pad;

generating a current through the first electrostatic protection resistor;

sensing the voltage at the bond pad through the second electrostatic protection resistor such that the current flow therethrough is substantially equal to zero, and all of the current flowing through the first electrostatic protection resistor substantially flows through the precision current-setting resistor; and

adjusting the value of the current in the current-setting resistor to be equal to a predetermined reference current in response to the sensed voltage.