Method and apparatus to test for current in an integrated circuit
OwnerRobert J. Lippinventor
Life of this patent
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Abstract
Various methods and apparatus perform IDDQ testing using the input and output circuits typically associated with input and output pads of an integrated circuit. Under these methods, the number of tester channels and external circuit elements required for IDDQ measurements is minimized. In one embodiment, the IDDQ current is measured by sensing the voltage at either an input pad or an output pad. In another embodiment, an internal pull-up transistor of known resistance is used for current sensing. In another embodiment, a method and apparatus for performing IDDQ testing quickly are provided by disconnecting the primary power or ground bus line connections from the tester and using alternate connections to provide power to the circuit under test over the duration of the IDDQ testing.
Claims41
A method for measuring current in an integrated circuit having a plurality of connection pads, said plurality of connection pads including a first primary supply pad for connection to a first supply voltage source and a second primary supply pad for connection to a second supply voltage source, said first and second primary supply pads providing a path for supplying power to said integrated circuit, said method comprising the steps of:
- connecting a means for sensing current between said first primary supply pad and said first supply voltage source;
- selecting one of said plurality of connection pads other than said first and second primary supply pads, so as to provide a selected connection pad having the same voltage as the voltage of said first primary supply pad;
- and
- measuring the voltage at said selected connection pad, said voltage being indicative of the current in said means for sensing current.
A method for measuring current in an integrated circuit having a plurality of connection pads, said plurality of connection pads including a first primary supply pad for connection to a first supply voltage source and a second primary supply pad for connection to a second supply voltage source, said first and second primary supply pads providing a path for supplying power to said integrated circuit, said method comprising the steps of:
- selecting one of said plurality of connection pads other than said first and second primary supply pads, so as to provide a first selected connection pad connected to said first primary supply pad through a means for sensing current, said means for sensing current in said integrated circuit;
- attaching said first supply voltage source to said first selected connection pad;
- and
- measuring the voltage attained by said first primary supply pad, said voltage being indicative of the current in said means for sensing current.
A structure for measuring current in an integrated circuit having a plurality of connection pads, said plurality of connection pads including a first primary supply pad for connection to a first supply voltage source, a second primary supply pad for connection to a second supply voltage source, a first connection pad and a second connection pad, said first and second primary supply pads providing a path for supplying power to said integrated circuit, said structure comprising:
- means in said integrated circuit connected between said first connection pad and said first primary supply pad for sensing a current between said first connection pad and said primary supply pad;
- and
- means for transmitting to said second connection pad the voltage on said first primary supply pad, when said first primary supply pad is disconnected from said first supply voltage source, said voltage being indicative of the size of said current.
A method for measuring current in an integrated circuit having a plurality of connection pads, said plurality of connection pads including a first primary supply pad for connection to a first supply voltage source, a second primary supply pad for connection to a second supply voltage source, said first and second primary supply pads providing a path for supplying power to said integrated circuit, said integrated circuit further including a circuit for selectively providing a low-impedance current source from said first primary supply pad to a selected one of said connection pads other than said first and second primary supply pads, said method comprising the steps of:
- connecting a means for sensing current between said first primary supply pad and said first supply voltage source;
- connecting said selected one of said connection pads to said first supply voltage source and enabling said selectable low-impedance current source;
- disabling said selectable low-impedance current source;
- and
- measuring the voltage of said first primary supply pad, said voltage being indicative of the current in said means for sensing current.
A method for measuring current in an integrated circuit having a plurality of connection pads, said connection pads including a first primary supply pad for connection to a first supply voltage source and a second primary supply pad for connection to a second supply voltage source, said first and second primary supply pads providing path for supplying power to said integrated circuit, said method comprising the steps of:
- connecting a decoupling capacitor between said first primary supply pad and said second supply voltage source;
- connecting a sensing resistor for conducting a current between said first supply voltage source and said first primary supply pad;
- connecting a tester pin driver set to forcing mode to charge said decoupling capacitor to the voltage of said first supply voltage source;
- disabling said forcing mode of said tester pin driver;
- and
- measuring the voltage attained at said first primary supply pad, said voltage being indicative of the current in said sensing resistor.
A structure for measuring current in an integrated circuit having a plurality of connection pads, said connection pads including a first primary supply pad for connection to a first supply voltage source and a second primary supply pad for connection to a second supply voltage source, said first and second primary supply pads providing a path for supplying power to said integrated circuit, said structure comprising:
- a decoupling capacitor between said first primary supply pad and said second supply voltage source;
- a sensing resistor for conducting a current between said first supply voltage source and said first primary supply pad;
- a tester pin driver capable of charging said decoupling capacitor to the voltage of said first supply voltage source;
- and
- means for measuring the voltage attained at said first primary supply pad, said voltage being indicative of the size of said current.
A method for measuring current in an integrated circuit having a plurality of connection pads, said connection pads including a first primary supply pad for connection to a first supply voltage source, and a second primary supply pad for connection to a second supply voltage source, said first and second primary supply pads providing a path for supplying power to said integrated circuit, said method comprises the steps of:
- connecting a capacitor of known capacitance between said second supply voltage source and said first primary supply pad;
- charging said capacitor to the voltage of said first supply voltage source;
- disabling said charging step;
- and
- measuring, after a predetermined period of time from said disabling step, the voltages of said capacitor over a fixed time interval, said voltages being indicative of the current provided by said capacitor over said predetermined period of time.
A structure for measuring current in an integrated circuit having a plurality of connection pads, including a fist primary supply pad for connection to a first supply voltage source, and a second primary supply pad for connection to a second supply voltage source, said first and second primary supply pads providing a path for supplying power to said integrated circuit, said structure comprises:
- a capacitor of known capacitance connected between said second supply voltage source and said first primary supply pad;
- means for charging said capacitor to the voltage of said first supply voltage source;
- means for disabling said charging means;
- and
- means for measuring, after a predetermined period of time from said disabling of said charging means, the voltages of said capacitor over a fixed time interval, said voltages being indicative of the size of said current flowing during said predetermined period of time.
Dependencies are inferred from the claim text.