JPS58200170A - Current consumption measuring circuit - Google Patents

Abstract

PURPOSE:To eliminate complicated calculation for correction while improving the measuring accuracy and the frequency response by automatically performing a calculation for correction of a load current of an object to be measured by a circuit function. CONSTITUTION:An internal logic operation is performed for an object 5 to be measured based on binary-coded logic signals from a signal source 1 and the results are outputted. The output is applied to a detection circuit 2 and compared with the expected value thereof. Here, as the output of the object 5 goes to 'H', currents IR1-IRN flow through a load resistance 3. Output voltage V0 of a load current detection circuit 6 and a reference voltage for the object 5 are supplied to the input of a load current correction circuit 7 and the output thereof provides a voltage VS higher by a voltage generated of the circuit 6 than the reference voltage. As a result, the load currents IR1-IRN are cancelled out with current from the circuit 7 keeping the load current from flowing through a current consumption measuring circuit 4 and instead, only the current consumed in the object 5 being measured is supplied thereby assuring a highly accurate measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a circuit with a simple circuit configuration that measures power supply current consumed inside a device under test during a functional test of an electric circuit.

(Background Art) Figure 1 shows a conventional circuit diagram for measuring current consumption during a functional test. In Fig. 1, 1 is an input signal source for functional testing, 2 is a functional horizontal circuit using a comparator circuit, 3 is a load resistance R1 to RN during a functional test, 4 is a current consumption measurement circuit using an operational amplifier, and 5 is a device to be measured. The device under test 5, such as an electric circuit, especially an IC, is an input signal source for functional testing.
An internal logic operation is performed on the logic signal input of '11' or L11 level output from When the load resistor 3 and detection circuit 2 of ~RN are connected and the output level is 'H', R, ~
Through RN, the load current from IRI to IRN is (jN
Flows to D. When the output level is It L It, only the output 01i'F leaf current of IRIL -IRNL becomes -0. Also, at this time, the detection circuit 2 constantly monitors whether the output level of each output terminal matches the expected value.

The current consumption measuring circuit 4 measures the total sum of the current IDD connected to the VDD terminal of the device under test 5 and consumed inside the device under test and IR1 to IRN flowing out to an external load as an output current as lo.

1, = current consumption of DUT (device under test) + load current - = IDD + IRI-N = IDD -) IB
The load current IRO value in this total current varies depending on the size of the external load resistance and the number of ")I" output terminals, etc.
It shifts each time. Therefore, the conventional current consumption measuring method can only measure the current that always includes the current flowing to the external load circuit. Therefore, in order to carry out accurate measurements, there are disadvantages in that the value of the load resistance, the number of "H" output terminals, etc. must be constantly calculated and correction work is required.

(Problems to be solved by the invention) In order to eliminate the drawback of conventional current consumption measurement, which requires correction work using complicated calculations to compensate for the influence of external loads, the automatic correction device has a power supply terminal (
The inflow current from the power supply terminal and the outflow current (IR) to the load of the circuit under test (5) which receives current from the power supply terminal (VDD) and outputs the result of processing performed according to the human input signal to the load.
In a circuit that measures the current consumption, which is the following, the voltage (V
o)) and a load current detection circuit (6) that generates the voltage (
load current compensation for compensating the load current (IR) from the supply current by providing a voltage corresponding to the sum or difference between the power supply voltage (VDD) and the supply voltage (VDD) to the power supply terminal via a resistor (Rt); The current consumption measuring circuit includes a current consumption measuring circuit that measures a current obtained by subtracting a value compensated by the load current compensation circuit from among the current supplied from the power source to the power supply terminal.

(Structure and operation of the invention) FIG. 2 shows an embodiment of the present invention, in which 1 is an input signal source for testing a function, 2 is a function test detection circuit using a co/parator circuit, and 3 is a load during a function test. Resistance It, ~RN,
4 is a current consumption measurement circuit using an operational amplifier, 5 is a 611 connected
1 is a constant, 6 is a load current detection circuit using an operational amplifier, and 7 is a load current compensation circuit using an operational amplifier.

Next, the interconnection and operation of each of these circuits will be explained. The input terminal of the device under test 5 is connected to the functional test input signal source 1, and the output terminal is connected to the load resistor 3 and the detection circuit 2. The consumption current measuring circuit 4 and the load current compensation circuit 7 are connected to the VDD terminal. The 1 μmj pieces of the load resistor 3 are all short-circuited and connected to the input terminal of a load current detection circuit 6 whose reference level is 0. The output terminal of the load current detection circuit 6 is connected to the input of the load current compensation circuit 7. The output of the DUT 5 is “H” output from the functional test input signal source 1.
Or, based on the L" level logic signal, internal logic operation is performed and the result is outputted to the output terminal as 11" or "L I+ level. The detection circuit 2 detects this output.
H-"1." is constantly monitored during the functional test, compared with the expected value, and judgment processing is performed. At this time, a current of IR1=IRN flows through the load resistor 3 when the output of the object to be measured 5 becomes H'' level. The load current compensation circuit 7 can be realized by a circuit that combines an inverting amplifier and a differential amplifier using an operational amplifier.All others are conventional measurement circuits as explained in FIG. This is the same as IR1~IR
Since the current of N flows through the current detection resistor RL of the load current detection circuit with 0 as the reference level, there is a current at both ends of the detection resistor.
A voltage drop of k[V] occurs. The input of the load current compensation circuit 7 is the output voltage ■ of the load current detection circuit 6. and the reference voltage of the voltage supplied to the VDD terminal of the device under test 5 are applied, and by adding or subtracting these two voltages, the voltage generated by the load current detection circuit 6 is always lower than the vDD supply voltage. A high voltage Vs is generated. By connecting this voltage Vs to the VDD terminal of the device under test 5 via a resistor 7a having the same value as the detection resistor RL used in the load current detection circuit 6, a load current flows out from the output terminal of the device under test 5. (IR1 to IRN) are supplied with all (the same value of current) from the load current compensation circuit 7 and are apparently canceled, and no load current flows through the current consumption measurement circuit 4, so the Since only the current consumed inside the device 5 is supplied, it is possible to measure the current consumption with good accuracy.

As explained above, in the first embodiment, the correction calculation for the load current flowing out from the output terminal of the device under test 5 is automatically provided by the functions of the load current detection circuit and the compensation circuit. There are various advantages.

1. Complex correction calculations are incomparable.

2. The current consumption of the DUT and the load outflow current are unrelated, allowing for accurate measurement.

3. The external load resistance can be lowered to a value limited by the drive capability of the output terminal of the device under test, resulting in good frequency response.

4. The number of output terminals of the device under test is not a limiting condition for measurement.

In the first embodiment, the open-drain output format is explained using a P-CH and FET as the object to be measured, but if there is a current flowing out from the output terminal through an external load resistor, the function of the load current detection and compensation circuit will be used. A current correction effect occurs.

(11PNP) The case of the oven collector output of the transistor is shown in FIG.

(Figure 4 shows the case of source hollow output using 21N-Cl and FET.

FIG. 5 shows the case of emitter hollow output using a transistor (t:31 NPN).

Further, in the above embodiment, a current-to-voltage conversion circuit is used as the current consumption measuring circuit and the load current detection circuit, but the same effect can be obtained by using a Kelvin current sensing system. An example of this is shown in FIG.

The embodiments shown in FIGS. 3 to 6 are the same except for the output form of the object to be measured.

(Effects of the Invention) Since the present invention has a load current compensation circuit, it has the advantage that it can automatically compensate for the current flowing into the external load.
Since restrictions on the number of output terminals of the device under test and the size of load resistance are significantly relaxed, it can be used for measuring current consumption during functional tests.

[Brief explanation of the drawings] Figure 1 is a circuit diagram based on the conventional consumption current measurement method;
The figure is a circuit diagram of a first embodiment according to the measuring method of the present invention, and FIGS. 3, 4, 5, and 6 are circuit diagrams of other embodiments according to the present invention. 1...Input signal source for functional test 2...Function detection circuit using a comparator circuit 3...
Load resistance R1 to RN4 during functional test... Current consumption measurement circuit using an operational amplifier 5... DUT 6... Load current detection circuit using an operational amplifier 7... Load current detection circuit using an operational amplifier Patent Application: Hitoki Electric Industry Co., Ltd. Patent application agent Megumi Yamamoto −

Claims (1)

[Claims] Inflow current from the power supply terminal and outflow current (IR) to the load of the circuit under test (5) which receives current from the power supply terminal (VDD) and outputs the result of processing performed according to the input signal to the load. In a circuit that measures current consumption, which is the difference between
6), and the load current (IR ); and a current consumption measuring circuit that measures the current supplied from the power supply to the power supply terminal minus the value compensated by the load current detection circuit. Current consumption measurement circuit.