JPS60108761A - Measurement of current - Google Patents

Abstract

PURPOSE:To elevate the accuracy by feeding a current to be measured and a reference current to a first resistor and a temperature sensing element and a second resistor and a temperature sensing element connected in series to a current path to be measured integrated on a common semiconductor substrate to detect output of temperature sensing elements. CONSTITUTION:In a system 31 to be measured, a reference system 32 and an arithmetic system 33 integrated on one semiconductor substrate with a circuit to be measured, a temperature sensing element 13 is arranged close to a resistor 8 in the system 31 inserted in series into a current path to be measured while a temperature sensing element 14 is arranged close to a resistor 9 connected in series to the reference power source 12 in the system 32. In addition, a pulse signal is applied for a fixed time DELTAt to a common control terminal G of switching elements 10 and 11 in the systems 31 and 32, a current (i) to be measured and the reference current I are fed to the resistors 8 and 9 and changes in the outputs of the elements 13 and 14 are applied to a divider 17 through differentiators 15 and 16 of the system 33. Thus, the resistors 8 and 9 and the elements 13 and 14 can be formed in the same structure with the same geometric shape.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to semiconductor integrated circuit VFI (hereinafter referred to as IC).
The present invention relates to a current measuring method intended for use in electronic devices, and particularly relates to a current detecting method suitable for integrating a measuring circuit system together with a circuit system under test into an IC.

(Prior art and its problems) [Current measurement using C as a measurement target is, for example, bipolar I
This is generally done for the purpose of overcurrent protection of a specific circuit part of C, and it is a big problem to accurately measure the current with a simple measurement system.

Conventionally, in this type of field, current measurement has generally been performed using the following method.

As shown in FIG. 2, a resistor 3 is made by forming a diffusion layer 5 on a part of the semiconductor substrate 4 of the IC including the circuit under test (6 indicates a silicon oxide film, and 7 indicates an electrode). , this resistor 3 is connected in series to the current path to be measured.

Then, as shown in FIG. This is related to Ohm's law (i-V/R). This is described, for example, on page 514 of the Semiconductor Handbook published by Ohm Publishing.

However, in such a conventional current measurement method, manufacturing variations in the diffusion layer 5 that become the resistor 3 and
There was a problem in that highly accurate measurements could not be carried out due to the temperature characteristics of the diffusion resistance (the general trend of the temperature characteristics of the diffused resistance is shown in FIG. 3). In other words, in order to accurately set the current i, the resistance ft1R must be accurately known.

However, errors in the resistance value R due to manufacturing variations are unavoidable, and it is also unavoidable that the resistance value R changes with temperature as shown in FIG. Such errors in the resistance value R and temperature characteristics directly affect the measured value in the conventional current measuring method, and highly accurate measurement cannot be expected.

(Object of the invention) The object of the invention is to
An object of the present invention is to provide a current measurement method that can measure a circuit current with high accuracy without being affected by variations in IU structure or temperature characteristics of each element of an IC.

(Structure of the Invention) In order to achieve the above object, the second invention includes a first resistor inserted in series in the current path to be measured, and a second resistor disposed close to the first resistor. A first temperature sensing element, a second resistor, and a second temperature sensing element disposed close to the second resistor are integrated on a common semiconductor substrate, and the first temperature sensing element is integrated on a common semiconductor substrate.
An unknown current to be measured is applied to the resistor, and a known reference current is applied to the second resistor for a certain period of time. A second feeling? ! The present invention is characterized in that each change in the output of the element is detected, and the magnitude of the current to be measured is determined from the detected value.

(Picture 2 of Embodiment) FIG. 4 shows the configuration of a current measuring device constructed by applying the current measuring method of the present invention. This device is roughly divided into a system under test 31, a reference system 32, and an arithmetic system 33, but in this embodiment, all of these are integrated into one system together with the circuit under test.
It is assumed that an IC is formed on one semiconductor substrate.

The system to be measured 31 includes a resistor 8 and a switching element 10 inserted in series in a current path to be measured through which an unknown current to be measured i flows, and a temperature sensing element 13 disposed close to the resistor 8 .

! ! The quasi-element system 32 includes a resistor 9, a switching element 11, and
It includes a series circuit of a reference current source 12 and a temperature sensing element 14 placed close to the resistor 9.

The gates of the two switching elements 10 and 11 are connected to a common control terminal G, and upon receiving a pulse signal with a width Δt applied from the IIJIII system (not shown) to the control terminal G, the switching elements 10 and 11 are connected to a common control terminal G. It is turned on only for a certain period of time.

When the switching element 10 is turned on, an unknown current to be measured i is applied to the resistor 8. Also, switching element 1
1 is on, a known reference current 1o is applied to the resistor 9 from the reference current source 12.

The derivation system 33 includes a differentiator 15 that detects changes in the output of the temperature sensing element 13 and a differentiator 1 that detects changes in the output of the temperature sensing element 9.
6, and a divider 17 that calculates the 11 power ratio of both differentiators 15 and 16.
is included.

This calculation system 33 calculates the resistance of the resistors 8 and 9 when the resistors 8 and 9 are energized as described above.
The output changes of the temperature sensing elements 13 and 14 due to heat generation are detected respectively, and the magnitude of the measured current i is calculated from the detected values as described later.

FIG. 5 shows a specific structural example of the resistor 8 and temperature sensing element 13, where (△) is a plan view and (B> is b-bIi!).
FIG.

The resistor 8 is formed by forming a rectangular ring-shaped P-type enlarged layer on an N-type semicircular JJ plate 26, and the electrodes 20 and 21 serve as image terminals.

The temperature sensing element 13 is formed inside the rectangular ring resistor 8, and in this example, an N-junction diode is used as the temperature sensing element.

That is, a P-type anode region 25 is formed on an N-type substrate 26, and an N-type cathode region 24 is further formed in a part of the anode region 25, and electrodes 22 and 23 are connected to each of them. Note that 27 indicates a silicon oxide film.

This J: sea urchin resistor 8 surrounds the temperature-sensitive cord 13,
The heat of the resistor 8 is effectively transferred to the temperature-sensitive cable 13.

Although the resistor 9 and temperature-sensitive element 14 of the group 11 system 32 are not shown, they are made with the exact same structure as in FIG. located close together. In other words, resistors 8 and 9, and temperature sensing element 1
3 and 14 are each formed in the same structure and the same geometric shape, and their properties are very uniform.

Next, the current measuring method of the present invention will be explained based on the above configuration. Switching elements 10 and 1 except during measurement
1 is set to A off, and they are turned on for a certain period of time Δt during measurement.

When a current to be measured i is applied to a resistor 8 having a resistance value R for a time Δt, the resistor 8 generates heat of Q=i''RΔt and increases the humidity of itself and the surrounding area. The temperature UT detected by the temperature-sensitive cable 13 disposed close to each other increases.

In exactly the same way, when the reference current r0 is applied to the resistor 9 having a resistance value R8 for a time Δ[, the resistor 9 becomes Qo-To'Ro
It generates heat of Δ1, raising the temperature of itself and its surroundings by 4. As a result, the temperature To detected by the temperature sensitive cable 14 disposed close to this rises.

As a result of measurement using the element having the structure shown in FIG. 5, the energization time of the resistor 8, the N current i, and the temperature change detected by the temperature sensing element 13 are as shown in FIG.

As shown in Fig. 6, in a region where the current conduction time is shorter than to (several ns), the temperature rise due to heat generation is determined only by the heat capacity of the semiconductor chip, so it is proportional to the current conduction time, and the temperature increase rate dT/ dt is proportional to the current i as shown in Figure 7,
It was found that

When the current application time becomes tOJ, the above-mentioned linearity is lost due to the effect of the heat dissipation of the chip itself.

The above-mentioned pulse width Δ[ (current application time during measurement) is the above-mentioned time t. is set smaller.

The relationship between heat generation and temperature rise described above is based on the resistor 8.
This also applies to the resistor 9 and temperature-sensing cable 14, which have the same structure as the temperature-sensing element 13.

By the way, when diodes are used as the temperature sensing elements 13 and 14, the temperatures T and To are detected by the forward voltage of each diode. As is well known,
The forward voltage of a diode is proportional to its temperature.

Now, the differentiator 15 determines the temperature change rate d'r/dt from the output of the temperature sensing element 13, and similarly, the differentiator 16 determines the temperature change rate dT from the output of the temperature sensing element 14.

/dt is detected. Also, in the divider 17, both differentiators 15.
The output ratio (dTo/dt)/(dTo/dt)-P of 16 is found.

This value P is equal to the current ratio i/T o, so the unknown measured current i is equal to the known base tI! Current■. and the above P, it can be determined that 1=IoXP.

In the current measurement method described above, since the resistor 8 and temperature sensing element 13 of the system under test 31 and the resistor 9 and temperature sensing element 14 of the reference system 32 have the same structure, their characteristics are uniform in the rC process. You can easily make things.

In addition, in the above method, since the unknown current value i is calculated from the temperature rise rate ratio P, even if the resistor 8.9 has the temperature characteristics as shown in FIG. Temperature sensitive cord 13
．． Even if there are variations in the process or heat in 14, the influence is canceled out to a great extent, and the measurement result is not affected, which is a great advantage. In other words, highly accurate current measurement can be easily performed.

In the above explanation, a diffused resistor was used as the 1j film resistor, and a diode was used as the temperature-sensitive element, but as is clear from the spirit of the present invention, the resistor and temperature-sensitive cord are not limited to these. , bare elements with uniform characteristics may be used.

For example, a membrane resistor such as a polysilicon resistor can be used as the resistor, and a bipolar transistor can also be used as the decline sensor. These are Ic
It is only a matter of selecting an appropriate bamboo material for matching the process.

Furthermore, the components other than the resistor 8/temperature sensing element 13 and the resistor 9/temperature sensing element 14 do not necessarily have to be integrated on the same semiconductor substrate.

(Effects of the Invention) As explained in detail above, according to the current measurement method according to the present invention, current measurement of an appropriate circuit under test in an IC can be performed by:
Unaffected by variations in the current detection resistor and temperature characteristics,
This can be done with high precision. Further, process variations in the current measurement system are not a problem, and these can be easily integrated into an IC.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a conventional current measurement method, Fig. 2 is a structural diagram of a detection resistor used in conventional current measurement, and Fig. 3 is a diagram showing an example of the temperature characteristics of the resistance value of the detection resistor. FIG. 4 is a block diagram of a measurement system to which the current measurement method according to the present invention is applied, and FIG. Sectional view, No. 6
Figures a3 and 7 are characteristic diagrams showing the changes in the energizing time and energizing current to the resistor and the temperature detected by the temperature sensing element shown in FIG. 5. 8......First resistor 9...
・・・・・・Second 11℃ antibody 13・・・・・・・・・
・Temperature-sensing element 14 of middle tube 1... 2nd
Temperature sensing element 15.16 Differentiator 17 Divider special V [Applicant Nissan Motor Co., Ltd.

Claims (2)

[Claims] (1) A first resistor inserted in series in the current path to be measured, a first temperature sensing element placed close to the first resistor, a second resistor, and a second resistor. A second temperature sensing element disposed close to the resistor is integrated on a common semiconductor substrate, and an unknown current to be measured is applied to the first resistor, and a known current is applied to the second resistor. A reference current is applied to each of them for a certain period of time, and changes in the output of the first and second temperature sensing elements due to the heat generation of the first and second resistors due to this energization are detected, and from the detected values. A current measuring method characterized by determining the magnitude of the current to be measured. (2) The first and second resistors and the first and second temperature sensing elements are each formed in the same structure and the same geometric shape. A current measuring method according to claim 1.