Built-in current sensor for I.sub.DDQ testing
First Claim
1. A method for detecting faults in an integrated circuit powered from a supply voltage VDD, composing the steps of:
- sinking current drawn by the integrated circuit during each interval that the circuit undergoes a logic transition;
sensing the current drawn by the integrated circuit during intervals other than when the integrated circuit undergoes a logic transition;
translating the sensed current to a corresponding sensed voltage;
comparing the sensed voltage to a reference voltage representative of a quiescent current expected to be drawn by the integrated circuit during intervals other when the integrated circuit undergoes a logic transition;
generating an indicating voltage in accordance with a difference between the sensed and reference voltages so as to indicate whether the quiescent current of the integrated circuit is above a expected quiescent current; and
stabilizing the indicating voltage against variations in the supply voltage VDD.
1 Assignment
0 Petitions
Accused Products
Abstract
A current sensor (10), for sensing a quiescent current (IDDQ) drawn by an integrated circuit (12) from a supply voltage VDD includes a current sink and voltage transducer (14) for sinking current from the integrated circuit during a logic transition and for providing a voltage indicative of the quiescent current when the circuit operates in its quiescent state. A comparator (18) compares this voltage to a reference voltage representative of a prescribed quiescent current. The comparator is coupled to a preamplifier stage (38) which serves to generate an indicating voltage in accordance with the comparator output signal. The indicating voltage from the preamplifier stage is stabilized by a stabilizing circuit (58) against variations in the supply voltage VDD to assure that the indicating voltage provides an accurate measure of whether the quiescent current IDDQ is above or below a prescribed current.
89 Citations
12 Claims
-
1. A method for detecting faults in an integrated circuit powered from a supply voltage VDD, composing the steps of:
-
sinking current drawn by the integrated circuit during each interval that the circuit undergoes a logic transition; sensing the current drawn by the integrated circuit during intervals other than when the integrated circuit undergoes a logic transition; translating the sensed current to a corresponding sensed voltage; comparing the sensed voltage to a reference voltage representative of a quiescent current expected to be drawn by the integrated circuit during intervals other when the integrated circuit undergoes a logic transition; generating an indicating voltage in accordance with a difference between the sensed and reference voltages so as to indicate whether the quiescent current of the integrated circuit is above a expected quiescent current; and stabilizing the indicating voltage against variations in the supply voltage VDD. - View Dependent Claims (2, 3, 4)
-
-
5. A current sensor for measuring a quiescent current drawn by an integrated circuit, when supplied with a supply voltage VDD, to detect possible faults, comprising:
-
a current sink and voltage transducer coupled to the integrated circuit for sinking current from the integrated circuit during intervals that the integrated circuit undergoes a logic transition and for providing a voltage in accordance with a quiescent current in the integrated circuit drawn during intervals other than when the integrated circuit undergoes a logic transition; a voltage comparator for comparing the voltage provided by the current sink and voltage transducer to a reference voltage representative of a prescribed quiescent current for the integrated circuit; a pre-amplifier stage coupled to the voltage comparator for providing an indicating voltage varying in accordance with a difference between the voltage provided by the current sink and voltage transducer and the reference voltage; and a stabilizing stage coupled to the pre-amplifer stage for stabilizing the indicating voltage against variations in the supply voltage. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12)
-
Specification