JPH0756502B2 - Electronic device drive circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for an electronic device having pins that require termination.

[Prior Art] As a conventional example of such an electronic device drive circuit, an electronic device drive circuit used in an inspection system for electronic devices such as ICs will be described with reference to FIG.

In this figure, 100 is a three-state driver, which receives a drive control signal and DC voltage VIH,
VIL is applied. The output of the driver 100 is connected via a signal transmission path 104 to a pin connection terminal 106 to which a device pin of the electronic device under test is connected. Output impedance of driver 100 and signal transmission path 104
A resistor 102 (for example, 50Ω) is inserted for matching with the characteristic impedance of the.

In the output mode (pin drive mode), the driver 100 is in the active state and outputs one of the DC voltage VIH or VIL designated by the drive control signal as the drive voltage,
It is applied to pin connection terminal 106. In the input mode, the driver 100 is in a high impedance state. In this input mode, the signal output to the pin of the electronic device is checked by a comparator or the like not shown.

Now, some electronic devices require termination of pins (eg ECL devices, MOS devices). If you need to drive an electronic device that requires such termination,
Conventionally, as shown in FIG. 2, a terminating resistor 110 (for example, 50Ω) and a terminating power source 112 are connected to a pin connection terminal 106 via a reed relay 108.

The electronic device drive circuit as shown is generally provided in a portion called a test head, which is a portion that directly interfaces with the electronic device.
There are many corresponding pins for electronic devices.

[Problems to be Solved] Now, the reed relay 108 is set to the closed or open state regardless of the mode. Even with such a configuration, ECL
There is no particular problem with the output pins of devices.

However, for input / output pins such as ECL devices that require termination, when the reed relay 108 is normally closed, the applied voltage (driving voltage) of the input / output pin during output mode (driving mode) is It will be affected by the connection of the terminating resistor. For that reason, conventionally, there has been a problem that the inspection must be performed without terminating the input / output pins of the ECL device or the like.

In order to solve this problem, it can be considered to open / close the reed relay 108 according to the mode. However, the response speed of the reed relay is generally considerably slower than the operation speed of high-speed electronic devices such as ECL devices. On the other hand, EC
When inspecting high-speed electronic devices such as L devices,
Need to switch modes fast.

Therefore, when handling ECL devices, etc., reed relay 1
Since it is impossible to open and close 08 by following the switching of the input / output mode, the reed relay 108 has to be always closed or opened, and the above problem cannot be solved yet.

[Object of the Invention] In order to solve such a problem, an object of the present invention is to connect and disconnect a termination circuit at high speed according to a mode, and also to provide a necessary termination for input / output pins of a high-speed ECL device. It is to provide an electronic device drive circuit capable of performing

[Means for Solving the Problems] The features of the electronic device drive circuit of the present invention that achieves such an object are that a three-state driver that operates in response to a drive control signal and an output of this driver are used as an electronic device. Resistance for matching and terminating the transmission line connected to the pin's connection terminal and the characteristic impedance of this transmission line inserted between the driver output and this transmission line, and opening / closing in response to the drive control signal. It is equipped with a high-speed electronic switch and a power supply for termination that is connected via the high-speed electronic switch at any point of the line from the driver output to the resistor. When the drive voltage is applied and the electronic switch is opened, the power supply for termination is disconnected and the driver is in a high impedance state in the input mode. Then, the electronic switch is closed and the terminal power supply is connected to the output of the driver.

[Function] Since the terminal power supply is connected and disconnected by the high-speed electronic switch that responds to the drive control signal, the terminal power supply is connected in the input mode and output mode even in the case of a high-speed electronic device such as an ECL device. Can be separated. Therefore, an input / output pin such as an ECL device that needs to be terminated can be driven by applying a drive voltage that is not affected by the termination power supply in the output mode, and can be terminated in the input mode.

Moreover, since the termination resistor and the impedance matching resistor are used in common, the number of parts is also reduced.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of an electronic device drive circuit according to the present invention. The electronic device drive circuit used in the electronic device inspection system will be described here.

In FIG. 1, reference numeral 10 denotes a three-state driver, which includes diode bridges 12 and 14, PNP type bipolar transistors 16 and 18, and NPN type bipolar transistors 20 and 22. The pair of nodes of the diode bridges 12 and 14 are connected to constant current sources 24 and 26, respectively, via bipolar transistors 16 to 22 as shown.

28 is a programmable power supply that supplies the DC voltage VIH to the driver 10, and 30 is a programmable power supply that supplies the DC voltage VIL to the driver 10. The DC voltages VIH, VIL are applied to one node of the diode bridges 12, 14 as shown.

PH, PH *, PL, PL * are partial signals of the drive control signals supplied to the electronic device drive circuit, and are applied to the bases of the corresponding ones of the bipolar transistors 16 to 22 as shown in the figure. By these signals, the bipolar transistors 16 and 20 or the bipolar transistors 18 and 22 are turned on in the output mode, the driver 10 is activated, and the direct current voltage VIH or VIL is output as the pin drive voltage. On the other hand, in the input mode, the bipolar transistors 16 to 22 are all turned off and the driver 10
Becomes a high impedance state.

The output of the driver 10 (the mutually coupled node of the diode bridges 12 and 14) consists of impedance matching and termination resistors (eg 50Ω) 32 and a signal transmission line 34 (eg a microstrip line with a characteristic impedance of 50Ω). It is connected to the pin connection terminal 36 via.

A terminating power source 38 is connected to the output of the driver 10 via a high-speed electronic switch 40 and a reed relay 42. This high-speed electronic switch 40 includes a diode bridge 44 and PNP-type and NPN-type bipolar transistor transistors 46 and 46 interposed between two opposing nodes of the diode bridge 44 and the constant current sources 24 and 26. It consists of 48. Diode bridge 44
Of the remaining two nodes, one is connected to the terminating power supply 38 and the other is connected to the output of the driver 10.

I / O and I / O * are partial signals of the drive control signal and are applied to the bases of the bipolar transistors 46 and 48.
The high-speed electronic switch 40 is closed in the input mode of the drive circuit and opened in the output mode in response to the I / O signal and the I / O * signal.

The reed relay 42 is opened when an input pin that does not require termination is connected to the pin connection terminal 36, and the reed relay 42 is closed when a pin that requires termination or an input / output pin is connected. .

Next, the operation of this electronic device drive circuit will be described. First, in the output mode (driving mode), the PH signal and PH * signal or the PL signal and PL * signal, which are complementary signals, are turned on at the same time.

For example, if the PH signal and the PH * signal are turned on, the bipolar transistors 18 and 22 are turned on at the same time, and the diodes of the diode bridge 14 are forward biased by the constant current sources 24 and 26. Therefore, the DC voltage VIH appears at the output of the driver 10 through the diode bridge 14, and this becomes the pin drive voltage at the pin connection terminal 36.
Is driven to drive the pins of the electronic device connected to the pin connection terminal 36.

When the PL signal and the PL * signal are turned on, the bipolar transistors 16 and 20 are turned on, each diode of the diode bridge 12 is forward biased, and the DC voltage VIL is output from the driver 10.

On the other hand, in this output mode, the complementary signals I / O signal and I / O * signal are turned off and the bipolar transistor 46,
To turn off 48, each diode in diode bridge 44 is reverse biased. Therefore, the high-speed electronic switch 40 is in the open state, and the termination power supply 38 is the driver.
Disconnected from 10 outputs.

In the output mode, the termination power supply 38 is
Since it is disconnected from the output of 10, the pin drive voltage is not adversely affected as when the power supply for termination is always connected.

In the input mode, the PH signal, the PH * signal, the PL signal, and the PL * signal are all turned off, and the bipolar transistors 16 to 22 are turned off, so that the diodes of the diode bridges 12 and 14 are reverse biased. Therefore, the driver 10 is in a high impedance state.

On the other hand, in the input mode, the I / O signal and the I / O * signal turn on at the same time, turning on the bipolar transistors 46, 48.
Each diode is forward biased. Therefore, the high speed electronic switch 40 is closed, connecting the terminating power supply 38 to the output of the driver 10. In this way, the pin of the electronic device connected to the pin connection terminal 36 is terminated, and the output signal of the pin is checked by a comparator (not shown) or the like.

When inspecting a high-speed electronic device such as an ECL device, the mode switching as described above is performed at high speed. As a matter of course, regarding the input / output pins, it is necessary to connect / disconnect the terminal power supply 38 at high speed in synchronization with the mode switching. Here, the response of the high-speed electronic switch 40 is much faster than that of a reed relay, and such a high-speed connection,
Can be cut.

Therefore, according to the electronic device drive circuit of this embodiment, the input / output pins of a high-speed device, such as an ECL device, which needs to be terminated, can be inspected by performing necessary termination and applying a normal drive voltage. Is possible.

Although one embodiment has been described above, the present invention is not limited to this. For example, the driver may be configured to drive the current booster with an operational amplifier, and the high-speed electronic switch may be replaced with another one using a semiconductor switching element capable of high-speed operation.

Other than this, various modifications are possible without departing from the scope of the present invention.

Further, it goes without saying that the present invention can be similarly applied to an electronic device drive circuit used for purposes other than the electronic device inspection system.

[Effects of the Invention] As described in detail above, the present invention provides impedance matching and termination between the output of a three-state driver that operates in response to a drive control signal and the pin connection terminal of an electronic device. A resistor is inserted, and the power supply for termination is coupled to the output of the driver through a high-speed electronic switch that opens and closes in response to a drive control signal, and the driver becomes active in the output mode and the drive voltage is applied to the pin connection terminals. A structure in which the electronic switch is opened and the terminating power supply is disconnected when the voltage is applied, the driver is in a high impedance state in the input mode, and the electronic switch is closed to connect the terminating power supply to the output of the driver. Therefore, I / O pins that require termination of high-speed electronic devices such as ECL devices are also output mode. Sometimes it is possible to drive by applying a drive voltage that is not affected by the power supply for termination, and it is possible to terminate in the input mode. Also, by combining the termination resistor and the impedance matching resistor, the number of parts is small and excellent electronic device drive is possible. A circuit can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing an embodiment of an electronic device drive circuit according to the present invention, and FIG. 2 is a schematic circuit diagram showing a conventional electronic device drive circuit. 10 …… driver, 12,14,44 …… diode bridge,
16,18,20,22,46,48 …… Bipolar transistor, 24,26
...... Constant current source, 32 ...... Impedance matching and termination resistors, 34 ...... Signal transmission line, 36 ...... Pin connection terminal, 38 ...
… Terminal power supply, 40… High-speed electronic switch.

Claims (1)

[Claims] 1. A drive circuit for an electronic device having a pin that requires termination, which is a three-state driver that operates in response to a drive control signal, and the output of this driver is connected to a pin connection terminal of the electronic device. A transmission line to be connected, a resistor for matching and terminating the characteristic impedance of this transmission line inserted between the output of the driver and this transmission line, and a high-speed electronic switch that opens and closes in response to a drive control signal. , A terminating power supply coupled through the high-speed electronic switch at any point of the line from the output of the driver to the resistor, the driver being in an active state in the output mode, and driving voltage to the connection terminal. Is applied, the electronic switch is opened to disconnect the terminating power source, and the driver is set to the high impedance mode in the input mode. Together becomes the scan state, the electronic device driving circuit and the electronic switch, characterized in that to connect the power for the termination in the closed state to the output of said driver.