SU1297017A2 - Device for tolerance checking of currents - Google Patents

Abstract

The invention relates to electrical measuring equipment and can be used for automated control of the currents of electronic circuits, in particular, in the control of integrated circuits, and is an improvement of the invention according to the author. N 1128224. The purpose of the invention is to improve the accuracy of controlling small currents. The device contains a control unit 1, programmable sources 3, 7, 16 voltages, a comparator 12, keys 21, 24, 26 controlled from unit 1, a voltage follower 25, a current-measuring resistor 20, programmable resistors 22 and 23, compensations a capacitor 58 and a controlled source 35 for compensating leakage current. The newly introduced controlled source 35 of compensating leakage current in preparation for measurements (and further periodically) adjusts to compensate for leakage currents in the measuring line and other elements associated with it (keys, amplifier inputs, etc.). Due to this, the accuracy of automatic control of small currents (in the range of 1-100 nA) is significantly improved. Controlled source 35 for compensating leakage current is implemented on the basis of three amplifiers, two programmable resistors and four additional resistors. 1 hp fl1, 2 ill. i (lu so-4 N) pye.1

Description

The invention relates to electrical measuring equipment and can be used for automated control of currents of electronic circuits, in particular for controlling integrated circuits,

The purpose of the invention is to improve the accuracy of control of small currents.

FIG. 1 shows the block diagram of the device; Fig. 2 is a block diagram of the control unit.

The device contains a control unit 1, the first output 2 of the control unit, a programmable source 3 napW

output from the terminal, calculating the voltage of source 7 during calibration, converting voltage values into codes for programmable resistors, calculating the compensation value (its current, etc.

In the random access memory (RAM) 51, variable data such as the magnitude of the test voltage to be set, the limit value of the monitored current, the magnitude of the delays between the switching on of different units and keys are stored. These data are entered into RAM 51 with a termination, amplifier 4, resistors 5 and b, la 54 under microprocess control

boundary value source 7, amplifier 8, resistors 9 and 10, second output 11 of control unit, comparator 12, amplifier 13, with mimic resistors 14 and 15, programmable voltage source 16, amplifier 17, input resistor 18, third output 19 of control unit, current-measuring resistor 20, key 21, programmable resistor 22, programmable resistor 23, key 24, voltage follower 25, key 26, controlled electronic circuit 27, fourth to ninth outputs 28–33 of the control unit, input 34 of the control unit of the control a compensating current source 35, y Or the plug 36, the input adjustable resistor 37, the first feedback resistor 38, the summing resistor 39, the amplifier 40, the second feedback resistor 41, the current setting resistor 42, the amplifier 43 limiting resistor 44, the tenth output 45 of the control unit, the microprocessor 46 , controller 47, synchronizer 48, highway 49, permanent memory 50, random access memory 51, interrupt processing unit 52, timer 53, terminal 54, input-output unit 55, reference voltage source 56, load C 57 and measuring capacitance lines and corre tiruyuschuyu capacity

.

The device works as follows.

The operation of all the main elements is controlled by the control unit 1, implemented on the basis of the microprocessor 46. The permanent memory device (ROM) 50 stores control programs for various preparation and measurement modes. These programs contain subroutines cb

output from the terminal, calculating the source 7 voltage during calibration, converting the voltage values into codes for programmable resistors, calculating the compensation value (its current, etc.

In the random access memory (RAM) 51, variable data such as the magnitude of the test voltage to be set, the limit value of the monitored current, the magnitude of the delays between the switching on of different units and keys are stored. These data are entered into RAM 51 from a terminal 54 under microprocess control.

25

-

ra 46 on the input routine. In addition, the transformed codes of programmable voltage value resistors are stored in RAM 51. These codes are formed during the input of information from the terminal.

The process of monitoring the current of the electronic circuit 27 begins with the input of a corresponding directive from the terminal. Meanwhile, interrupt handling unit 52 generates an interrupt request signal. The microprocessor 46 inserts an interrupt enable signal, the interrupt vector and, through the I / O unit 55, provides codes to the controlled voltage and current sources, as well as control signals to turn the reference voltage on and off. The synchronization of the monitoring process, the formation of keys and sources for switching on and off, is carried out by timer 53. The synchronizer 48 provides the microprocessor 46 with a clock frequency. The result of the control from the comparator 12

40 via input 34 and input / output unit 55 is received by microprocessor 46 and stored. Next, a new measurement begins or the monitoring process ends.

45

At the request of the terminal 54, it is possible to call from the RAM 51 the value of the set limit value of the monitored current, and also the result

50 control - more or less than the norm. The indication can also be caused by the measured leakage current and the voltage values at the outputs of the voltage sources.

Before the device starts operation, an auto calibration is performed, in which the leakage currents are compensated in the measuring lines, keys 21 and 26, repeater 25. It

55

3129

is carried out when the controlled electronic circuit 27 is absent.

In this mode, the device operates in the following sequence.

Initial state. The control unit 1 supplies the inputs of the resistors 6, 10, 18 and 37 with a voltage equal to 0. The key 26 is open, and the keys 21 and 24 are closed in accordance with the codes from the outputs 28, 29 and 31 of the control unit 1. The ratio of the programmable resistors 5 and 6 to the commands of block 1 is set so that after the transfer to the resistor 6 of the reference voltage at the output of source 3 there is a test voltage (i.e., the voltage at which the current will be measured). Accordingly, the rotation of the resistors 18 and 22 is set so that after applying the reference voltage to the resistor 18 at the output of the programmable source 16, the voltage equal to the test voltage is established In the initial state at the output of the controlled source 35, the current is adjustable resistor, 37 is supplied with zero voltage from block 1. Thus, in the initial state, the output voltage of the device is set to zero and the necessary values of resistors are set. At the input of the comparator 12 there is a zero voltage.

Leakage current measurement. On commands from the outputs 28 and 29 of the control unit 1, the key 26 is closed, the key 24 is opened. The input voltage of source 3 (resistor 6) of block 1 is supplied with a reference voltage, as a result of which a voltage equal to the test voltage is established at the output of source 3. The reference voltage is supplied from source 56 and may be of any polarity. The output voltage of the source 3 through the closed key 26 is fed to the output of the device (in Fig. 1 - the input of the controlled electronic circuit 27). At the same time, a reference voltage is also applied to the input of source 16 (to input resistor 18). At the same time, a voltage is set at its output, equal to the voltage at the output of source 3. The charging time of tanks C and C,

. H N,

through the output impedance of sources 3 and 16 will be determined by the intrinsic time of establishing the voltage at the outputs of these sources, since their output impedance is close to zero, as a result

The transition process is less than 0.1 ms. After the completion of the transient process, the voltage across both terminals of the current-measuring resistor 20 will be the same, so current does not flow through the resistor.

The control unit 1 supplies the voltage to the input of source 7. At this, the voltage at its output is also set equal to the test one (i.e., the same value as the output of sources 3 and 16). The keys 21 and 26 open, and the key 24 closes. In this case, the ratio of resistors 18 and 23 is set such that a voltage equal to the test voltage is set at the output of the source 16 (i.e., the same as the output of the source 3).

Thereafter, a transient occurs, which, depending on leakage currents at the device output, can proceed in two ways.

If the leakage current is zero, there will be no transient and the voltage at the output of the source 16 remains unchanged, which is fixed by the comparator 12.

If the leakage current is different from zero, then the voltage at the output of source 16 begins to change due to negative feedback through a resistor 20 that is connected. one output to the output of the amplifier 17, and the other to the input of the device, i.e. to the line to the controlled electronic circuit 27 and further through the repeater 25, the key 24 and the programmable resistor 23 - to the input of the amplifier 17).

Depending on the sign of the leakage current, the voltage will either increase or decrease relative to the test voltage (i.e., the voltage at the output of source 3) until a certain constant value is reached.

The magnitude of the steady state voltage at the output of the source 16 is determined as follows.

By changing the ratio of resistors 9 and 10 to the commands of control unit 1 at the output of source 7, a voltage equal to the voltage at source output 16 is set. The moment of equality of the voltages at the outputs of sources 7 and 16 is fixed by a comparator 12, from which the corresponding signal is supplied to control unit 1 (at the entrance 34).

5Ч297017

On this signal, block 1 calculates

on ra

leakage current

Uij - UMCP

I according to the formula

at

R

(one)

And} and

Where

and.

and..

R.,

steady-state voltage at the output of source 16;

test voltage at the output of the device (the input of the line of the controlled electronic circuit the magnitude of the measuring resistor 20,

Key 26 is open, and keys 21 and 24 are closed. The voltage at the output of the programmable source 3 is zero, which is provided by the corresponding signal from the control unit 1, namely, to the output of the resistor of the programmable source 3 is supplied with zero voltage from the output 2 of the unit 1. The voltage at the output connected to the controlled electronic circuit 27 current measurement resis

From the calculated leakage current value, 20 is also set to

ki 1 ,, block 1 of the control is determined by the net. This is ensured by the fact that

the value of the adjustable - (programmable keys 24 and 21 are closed at the commands of my) resistor 37, necessary for

From outputs 29 and 31 of control unit 1, zero voltage is supplied to the input of programmable source 16 (to the output of resistor 10) from control unit 1. A zero voltage is also set at the output of the source of the 7 limit values. A controlled circuit 27 is connected to the device. With the help of resistors 5 and 6, a command from the output 2 of control unit 1 (in accordance with this

set the compensating current controlled source 35, according to the formula

Wod.B8 Q Th

(2)

and

- reference voltage, set by control unit 1 from output 45 to input of controlled compensating current source 35.

control block 1) is set

On a command from block 45 of block 1, the transfer ratio of the programmable programmable resistor 37 is set equal to the calculated value, and then to the input of the controlled source 35, block 1 i applies the reference voltage of the corresponding voltage source 3 so that after transfer to its input (the resistor 6) the reference voltage from control unit 1, the voltage across

35, the output of the programmable source 3 is set equal to the required voltage for the controlled electronic circuit 27.

sparse polarity. At the output of the controlled source 35, a current opposite to the leakage current 1y appears. The compensating flow is then corrected, for which the leakage current measurement is repeated in this way. The control unit calculates and sets a measured value of leakage current 1 to a new value of programmable resistor 37, which corrects the magnitude of the compensating leakage current at the output of the controlled source 35. The correction process continues until the voltage at the output of source 16 is not established equal to the test voltage with a given error (the magnitude of the error

50 from the output 32 of the block 1, the value of the resistor 22 is set such that, together with the resistor 18, to provide at the output of the programmable source 16 a voltage corresponding to that specified in block I). The process of calibrating the limit current of the current of the pin ends here. Its length of the circuit is 27, i.e.

the bone is about 10 R,

Almost the duration of the process

Calibration does not exceed UC ,, R

r (

± and

not

(3)

After the calibration is complete, the current control begins as follows.

Key 26 is open, and keys 21 and 24 are closed. The voltage at the output of the programmable source 3 is zero, which is provided by the corresponding signal from the control unit 1, namely, to the output of the resistor 6 of the programmable source 3, a zero voltage is applied from the output 2 of the unit 1. The voltage to the output connected to the controlled electronic circuit 27 current-measuring resistokey 24 and 21 are closed by commands

From the outputs 29 and 31 of the control unit 1, and the input to the programmable source 16 (to the output of the resistor 10) from the control unit 1 receives a zero voltage. A zero voltage is also set at the output of source 7 of the limit values. A controlled circuit 27 is connected to the device. With the help of resistors 5 and 6, a command from the output 2 of the control unit 1 (in accordance with this

programmable transfer coefficient

source 3 voltage so that, after transmitting to its input (resistor 6) the reference voltage from control unit 1, the voltage across

The output of the programmable source 3 is set equal to the required voltage for the controlled electronic circuit 27.

Reprogramming resistors

5 and 6 occurs at zero; m at the input of a programmable source 3.

On commands from outputs 19 and 30 of block 1, the ratio of resistors 18 and

23 is set so as to provide at the input of the controlled circuit 27 (the right terminal of the current measuring resistor 20) a predetermined test voltage. At the same time, from the output 32 of the block 1, the value of the resistor 22 is set such that, together with the resistor 18, the output of the programmable source 16 provides a voltage corresponding to the limit current of the counter (

± and

not

(3)

Where

.

- resistance of the current measuring resistor 20. Since all the switching resistors. The correction capacitance (C) is charged along the circuit: the output of the programmable source 16, the key 26 and the output of the programmable source 3,

Tori 23, 22 and 18 occur at equal- 5 The circuit has close to zero resistance to zero voltage at the input of the programmable source 16, then the voltage at the output of the controlled circuit 27 remains zero. Due to the presence of capacitance (Sc), in the control of my circuit 27 there are practically no voltage surges that occur at the time of the open circuit, which includes the repeater 25, the key 24 and the resistor 23 (when the resistor is 5). The reprogramming time of resistors 18.22 and 23 is significantly less than the time for setting the mode at the output of the controlled circuit 27, if the switch 26 is open.

The current-measuring resistor 20, at the command of control unit 1, is set to a value that corresponds to the required range of the monitored current. Upon a command from key 1, control key 26 closes, then key 24 opens. Then, the input voltage from block 1 is fed to the inputs of programmable source 3, programmable source 16, and source 7 of limit values. At the output of the second programmable source 3 A required test voltage 35 appears, which through a closed switch 26 goes to a controlled circuit 27 and charges the load and measuring line capacitance (C). At the same time, the controlled source 40 35 of the compensating current generates a current established during calibration, which compensates for the leakage current in the measuring line, the repeater input circuits, and the keys. The time of the establishment of voltage 45 U is determined, in the axis.

At the output of the source 7 of the boundary values, the voltage appears that goes to the first input of the comparator 12, the second input of which also receives the voltage U, p from the output of the programmable source 16. At the same time, a current flows through the Measuring resistor 20, which closes through the output source impedance 3.

Then the switch 24 closes and a negative feedback circuit is formed through the voltage follower 25, the switch 24 and the programmable resistor 23 to the second input of the programmable source 16. At the same time, taking into account the ratio of the values of the resistors 23 and 18, the voltage variations U ,, co are not occurs or it changes at a rate determined by the time constant of the circuit formed by the current sense resistor 20 and the correction capacitor C.

This time constant is tens ms. Therefore, the high-speed programmable source 3 holds the voltage almost unchanged. The scientific research institute is, moreover, that after a time less than 1 ms, the key 26 is opened by the command from the control unit 1. Further, the voltage is maintained due to negative feedback over the circuit: repeater 25, switch 24, and resistor 23.

If the current of the monitored circuit 27 differs from the limit value, the voltage at the output of the programmable source 16 begins to change at a rate determined by the constant time of the circuit formed by the current-measuring resistor 20, the correction capacitance C, capacitive load and the measuring line own time set If the current of the monitored circuit 27 differs from the limit value, then the voltage at the output of the programmable source 16 begins to change at a rate determined by the constant time of the circuit, Call clamp resistor 20, a correcting capacitance C, capacitive kostn) linovleni load and measuring a voltage at the output of programmable power supply 3, output impedance is close to zero. 50 NII C „and the input resistance of the controlled electronic circuit 27, and

At the same time, at the output of the program, the transmission coefficient of the programmed source 16 also sets the voltage U. corresponding to the limit value of the monitored current. The set time is equal to the own set time of the programmable source 16

source 16, defined by the ratio of the resistors 18 55 and 22 (the key 21 1g1).

Further, the key 21 is opened and the rate of voltage variation at the output of the programmable source 16

napr. The correction capacitance (C) is charged along the circuit: the output of the programmable source 16, the key 26 and the output of the programmable source 3,

The chain has a resistance close to zero.

the

At the output of the source 7 of the boundary values, the voltage appears that goes to the first input of the comparator 12, the second input of which also receives the voltage U, p from the output of the programmable source 16. At the same time, a current flows through the Measuring resistor 20, which closes through the output resistance programmable source 3.

Then the switch 24 closes and a negative feedback circuit is formed through the voltage follower 25, the switch 24 and the programmable resistor 23 to the second input of the programmable source 16. At the same time, taking into account the ratio of the values of the resistors 23 and 18, the voltage variations U ,, co are not occurs or it changes at a rate determined by the time constant of the circuit formed by the current sense resistor 20 and the correction capacitor C.

This time constant is tens ms. Therefore, the high-speed programmable source 3 holds the voltage almost unchanged. The scientific research institute is, moreover, that after a time less than 1 ms, the key 26 is opened by the command from the control unit 1. Further, the voltage is maintained due to negative feedback over the circuit: repeater 25, switch 24, and resistor 23

If the current of the controlled circuit 27 differs from the limit value, then the voltage at the output of the programmable source 16 begins to change with a speed determined by the constant time of the circuit formed by the current-measuring resistor 20, the correction capacitance C, the capacitance C and and the input resistance of the monitored electronic circuit 27, and

 also by the transfer ratio of

source 16, defined by the ratio of the resistors 18 55 and 22 (the key 21 1g1).

Further, the key 21 is opened and the rate of voltage variation at the output of the programmable source 16

912

increases. The direction of voltage change depends on whether the current to be controlled is greater than 1 or less.

After a time determined by the specified control error, the sensitivity of the comparator 12, the noise level at the output of the programmable source 16, as well as the rate of voltage variation at its output, the control unit 1 polls the comparator 12 at input 34. The comparator 12 detects the deviation (or stability ) tension. And that is where the measurement ends.

Thus, the accuracy of the automatic control of currents in the range of 1-100 nA is significantly improved by compensating for leakage currents in the measuring lines.

Claims (2)

1. Device for tolerance control of currents according to auth.St. No. 1128224, characterized in that, in order to improve the accuracy of control Editor I. Casard Compiled by V.Ivanov Tehred A. Kravchuk Proofreader A.T. Order 779/50 Circulation 864 Subscription VNII1Sh USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod7 Ul7 Proektna 7 4 710 of small currents, a controlled source of compensating current connected to the tenth output of the control unit is inputted to it, and an output to the input of a controlled electronic circuit. 2. The device according to claim 1, wherein the controlled source of the compensating current contains an input control resistor, a current-establishing resistor, a summing resistor, a limiting resistor, two feedback resistors and three amplifiers, the input of the first amplifier through the input adjustable the resistor is connected to the source input, and the output through the current-supplying resistor is connected to the source output and through the first feedback resistor to its own input, the source output is connected to the input of the second amplifier, the output of which is through A resistor is connected to the input of a third amplifier, connected by an output through a summing resistor to the input of the first amplifier and through a second feedback resistor to its own input.