The present invention relates to a driver circuit for outputting a load current to an electric device and an IC tester, and in particular, relates to a driver circuit integrated with a load current output circuit that functions as both a load current output circuit and a driver circuit while having smaller circuit scale and chip area than the scale and area required for two circuits, and which is also capable of reducing a electricity consumption to a level lower than what two circuits would consume, and pin electronics and IC tester having thereof.
In an IC tester, a test wave form is applied to a predetermined terminal to judge (hereinafter referred to as a judge mode), by the judge circuit thereof, whether a response waveform outputted from an output terminal (or input/output terminal) of a device under test (hereinafter referred to as DUT) such as a semiconductor after a predetermined time from the application of the test waveform is in a high level (hereinafter referred to as, xe2x80x9cHxe2x80x9d) or a low level (hereinafter referred to as, xe2x80x9cLxe2x80x9d) corresponding to a strobe signal generated with a predetermined timing (hereinafter referred to as a judge mode) so as to conduct an operation test or performance test or the like of the DUT by comparing the obtained result with an expected value. When judging a state of the response waveform in the above-described manner with respect to a nonterminal device, the judgment is performed by supplying, to a predetermined output terminal, a predetermined current value (a load current of about several mA to several tens of mA, for example) corresponding to an output waveform of either xe2x80x9cHxe2x80x9d or xe2x80x9cLxe2x80x9d. For the purpose thereof, the IC tester is provided with a load current output circuit for supplying a load current to the output terminal of the DUT during the judge mode.
The load current output circuit is normally connected to the output terminal via an internal diode switch circuit. The load current output circuit operates only under the judge mode, and does not output the load current while a driver connected to the output terminal is under operation and a voltage is being applied.
FIG. 9 is a diagram illustrating a circuit structure of a pin electronics of a conventional IC tester. The pin electronics 2 is constituted of a driver 20 for applying a voltage set in advance to a predetermined terminal of a device under test 25 (hereinafter, referred to as DUT), an output resistor 23, a comparator 21 for judging a state of response waveform outputted from the DUT 25, a load current output circuit 28 for receiving (or deriving) the load current or supplying a predetermined load current to the terminal when gaining the response waveform from the DUT 25. The DUT 25 is connected to the driver 20, the comparator 21, and the load current output circuit 28 via a transmission line 24. A number of pin electronics circuits prepared for is the same as a number of I/O pin of each device multiplied by a number of measurement devices, thereby respective response waveform (output waveform from the output terminal) is simultaneously level-judged with respect to a plurality of the DUT.
FIG. 10 is an output buffer circuit of a conventional driver. The output buffer circuit is constituted of an input stage push-pull circuit constituted of transistors Q1 and Q2, a first output stage buffer amp constituted of transistors Q3 and Q5 for receiving phase output of the push-pull circuit, a second output stage buffer amp constituted of transistors Q4 and Q6. The maximum output current of the driver is 60 mA, and the current of up to 60 mA flows though the transistors Q5 and Q6.
FIG. 11 is a current buffer circuit of a conventional load current output circuit. The current buffer circuit includes an input stage push-pull circuit constituted of diodes D1, D2, D3, and D4, and transistors Q1 and Q2, an output stage buffer amp constituted of transistors Q3 and Q4 for receiving a phase output of the push-pull circuit, and a diode switch circuit constituted of bridge circuits of diodes D5, D6, D7, and D8. The maximum output of the load current is 25 mA, and the current of up to 25 mA flows through the transistors Q3 and Q4 and the diodes D5, D6, D7, and D8. In the present example, the diode bridge circuit constituted of the diodes D5 to D8 is discretely structured.
As such, in the prior art, the output buffer circuit of the driver and the current buffer circuit of the conventional load current output circuit have many commonalities between their output stage buffer. Also, both of these circuits do not operate redundantly while the driver is under operation and the load current output circuit is under operation.
In the above-described conventional technique, the load current output circuit and the driver circuit are made up on separate chips, or even if on the same chip, they are made as a separate circuit. However, with such structure, an IC tester is becoming larger because a large number of pin electronics circuits are used due to an increased capacity of DRAM in recent years and an increased number of pins for the IC tester for improving testing efficiency due to higher throughput. Moreover, when a number of pins is increased, a problem such as an increase of electricity consumption thereof arises.
In the conventional technique, the output buffer circuit of the driver and the current buffer circuit of the conventional load current output circuit have many commonalities between their output stage buffers, and both circuits do not operate redundantly when the driver operates and the load current output circuit operates.
The present invention has been achieved in view of the above, and an object thereof is to provide a driver circuit integrated with a load current output circuit, and a pin electronics and an IC tester having thereof, which is capable of reducing a circuit scale and a chip area as well as electricity consumption thereof when the driver circuit and the load current output circuit for an electronics device are packed on one chip.
In order to achieve such object, a driver circuit integrated with a load current output circuit, and pin electronics and IC tester having thereof according to the present invention provides a driver circuit that functions as a load current output circuit for an electronics device and as a driver circuit, and includes a common buffer circuit that includes a current buffer circuit for the load current output circuit and the output buffer circuit for the driver circuit as a common circuit therefor.
These and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.