JPH01166552A - semiconductor integrated circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to semiconductor integrated circuit technology and to technology that is particularly effective when applied to control of internal voltage in semiconductor integrated circuits. This article relates to techniques that are effective for use in semiconductor integrated circuits.

[Prior Art] Conventionally, bipolar logic LSIs have been designed to change the constant voltage supplied to an internal constant current transistor in response to fluctuations in the externally applied power supply voltage, thereby reducing the current flowing through the circuit. A voltage compensation circuit that keeps the amplitude of the internal signal constant and keeps the reference voltage, such as the reference voltage applied to the reference transistor of the ECL logic gate, constant regardless of fluctuations in the power supply voltage. There are some that have built-in. Constant current circuits and constant voltage circuits are described, for example, in "Integrated Circuit Application Handbook" published by Asakura Shoten, June 30, 1981, pages 49 to 51.

[Problems to be solved by the invention] One of the diagnostics of logic LSIs is testing the operating margin of internal circuits, but LSs that do not have voltage compensation circuits as described above
In I, LSIs with small margins can be easily found and eliminated by changing the externally applied power supply voltage.

On the other hand, although an LSI having a voltage compensation circuit is an extremely effective method for eliminating the dependence of circuit delay time on power supply voltage, it produces extremely inconvenient results in operating margin tests. That is, in a logic LSI having a voltage compensation circuit, the amplitude of an internal signal does not change even if the external power supply voltage is changed, so the operating margin cannot be forcibly lowered. At first glance, there is an illusion that if an LSI passes the margin measurement method by manipulating the external power supply voltage, it can be considered a good product, but LSIs with small operating margins are susceptible to crosstalk that occurs internally. Malfunctions are likely to occur due to noise caused by noise, alpha rays, current switching, etc. Therefore, LSIs with small operating margins must be rejected as defective products.

However, for LSIs with voltage compensation circuits, diagnosis by manipulating the external power supply voltage as described above is ineffective, and an effective diagnostic method for detecting malfunctions due to internal noise as described above has not yet been developed. The current situation is that this is not the case.

Therefore, in LSIs with built-in voltage compensation circuits, there is a high risk that LSIs with small operating margins will be shipped as non-defective products.The purpose of this invention is to
Even in a logic LSI with a built-in voltage compensation circuit, an LSI with a small operating margin can be easily detected and reliably rejected as a defective product, thereby improving the reliability of the LSI.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means for Solving the Problems] Representative inventions disclosed in this application will be summarized as follows.

In other words, there are two types: a constant voltage that has a path that continues to flow a constant current regardless of fluctuations in the power supply voltage and is independent of the power supply voltage based on the potential on that constant current path, and a voltage that changes depending on the power supply voltage. In an internal voltage generation circuit that performs voltage compensation by generating a voltage, a transistor is provided that can flow a bypass current into or extract the bypass current from the constant current path, and this transistor can be controlled from the outside. An external control terminal is provided for this purpose.

[Function] According to the above-mentioned means, it is possible to freely control the internal voltage generated by flowing a bypass current into the constant current path in the internal voltage generating circuit or drawing the current out using a control signal from the outside. , this allows LSI
By forcibly reducing the operating margin when the circuit is turned off, defective products can be easily detected, and the above object of improving the reliability of the LSI can be achieved.

[Embodiment] FIG. 1 shows an embodiment in which the present invention is applied to a band gap reference type internal voltage generation circuit in an ECL type logic integrated circuit.

In the circuit shown in FIG. 1, the circuits surrounded by broken lines 1 and 2 are newly added circuits to realize the diagnostic function aimed at by the present invention. The internal voltage generating circuit except for the circuit indicated by the broken line 1.degree. 2 has the same structure as a generally known internal voltage generating circuit having a voltage compensation function.

To briefly explain the operation of the internal voltage generation circuits excluding the circuits indicated by broken lines 1 and 2, this circuit consists of a pair of transistors QztQ whose base terminals are commonly connected to each other.
iL, - Therefore, a transistor Q□ with a resistance R is connected in series between Vcc and VEE.

A current path consisting of resistor R2, transistor Q2, and resistor R3 includes transistors Q2. The value obtained by dividing the difference in voltage between the base and emitter of Q by the resistance value of resistor R1, that is, (V
a E2-v a l:a) A constant current I of the magnitude shown by /Ra is made to flow, and the current passed through this constant current path is as clear from the above equation. Depends on VBH and does not depend on power supply voltage VEE. In other words, it depends on the emitter size and process of transistor Q21Q, and once it is determined, it remains constant regardless of fluctuations in VEH. Also, since the same voltage is applied to the bases of transistors Q1 and Q, R4-
A constant current determined by the emitter sizes of Q2 and Q flows through the path Rs-RG Q□. Then, the emitter follower consisting of transistors Q, Q7, and resistor R7 is driven by the constant voltage divided by resistors R4 and R5 through which this constant current flows, so transistor Q
A constant voltage is output from the emitter terminal 6. In this embodiment, the emitter voltage of this transistor Q is changed to EC via a voltage follower 4a as shown in FIG.
It is supplied as a reference voltage VBB to the reference transistor Qr constituting the L circuit 3.

On the other hand, an emitter follower consisting of a transistor Q1 driven by the same voltage as the base potential of the transistor Q and a resistor R8 is provided, and
At the connection node nL between the resistor R2 and the transistor Q2 on the constant current path, there is a resistor R between the power supply voltage Vcc and VBH.
,,R. The base terminals of transistors Q, which are connected in series with each other, are connected.

Therefore, in this case, the potential Vn□ of node n□ is VEE
The base-emitter voltage VB of transistor Q
The voltage VEE+VBE is higher by E.

becomes. Therefore, a constant current flows through the resistor R2 as described above. Therefore, if the voltage at node n is constant, the potential at the connection node between transistor Q□ and resistor R2 is VEE+VBE, +R, ·I.

Therefore, the base voltage of Q□ is further VBE
, the higher voltage V E E +V e E, +R, ·1.
+VBE. Therefore, the emitter follower (Q,) is driven by the same voltage as this base voltage.

The output voltage of Ro) will change in the same way if the power supply voltage VEE changes.

In this example, this emitter follower (Q8°RS)
As shown in FIG. 2, the output voltage is supplied as a constant voltage Vcs to the base of the constant current transistor Qc of the current switch of the ECL circuit via the voltage follower 4b. However, since the same power supply voltage VEE as the internal voltage generation circuit is applied to the ECL circuit, if the voltage Vcs applied to the base of the constant current transistor changes in the same way when VEE changes, the base and emitter The potential difference becomes constant, and the flowing current also becomes constant. As a result, even if the Wi source voltage VEE fluctuates, the operating current flowing through the ECL circuit remains constant, and the amplitude of the signal also becomes constant. In other words, the operation of the ECL circuit is guaranteed against fluctuations in VEH.

In the internal voltage generation circuit having a voltage compensation function as described above, in this embodiment, a current supply transistor Q□ and a current extraction transistor Q1 are connected to a connection node n1 between the resistor R2 and the transistor Q2. □ was connected. Furthermore, a current supply transistor Q4. and a transistor for current extraction. The collector terminals and base terminals of transistors □ and Q13 for current supply were connected to external terminals A, E, B, and F, respectively.

Furthermore, current extraction transistors Q□2 and Q8. Its base terminal was connected to external terminals C and G, and its emitter terminal was connected to the external terminal and power supply voltage VEE through a resistor, respectively.

Therefore, in the internal voltage generating circuit of the above embodiment, appropriate voltages are applied to the external terminals A and B.

When a current flows into node n1 from transistor Q1□, the current flowing through transistor Q2 tries to remain constant as .
current decreases, and the base voltage decreases. As a result, the emitter voltage of transistor Q6, that is, the firing voltage Vcs decreases. On the other hand, if external terminals C and D are controlled to turn on transistor Q2 instead of transistor Q□1, node n1
Since current can be extracted from the transistor Q1, the current flowing through the transistor Q1 increases by that amount, and the base potential rises. As a result, the 1 generation voltage Vcs increases.

Also, by controlling the external terminals E and F, the transistor Q13
When turned on and current flows into node n2, the collector current of transistor Q4 is constant, so the current flowing through resistor R4 decreases. Therefore, the potential of the node n2 rises, and the 1 generation voltage Van rises. On the other hand, when the external terminal G is controlled to turn on the transistor Q14 and draw current from the node n2, the current flowing through the resistor R4 increases.

The potential of node n2 drops and the generated voltage VBB drops.

Therefore, the internal voltage generating circuit of this embodiment has an external terminal A
-G is opened or fixed to the lowest power supply voltage of the circuit via a high resistance element and operated, the generated voltage Vcs
fluctuates in the same way as the power supply voltage VEE, and the generated voltage VBB is f! It functions as a voltage compensation that remains constant regardless of fluctuations in the gta voltage VEE, and also allows the levels of the generated voltages Vcs and VBe to be freely changed by controlling the external terminals A-G as described above during LSI diagnosis. , an LSI with a small margin can be detected by intentionally reducing the operating margin.

Note that the circuit shown in FIG. 1 is a logic LS consisting of an ECL circuit.
It can be used not only for I but also for logic LSIs consisting of NTL (non-threshold logic) circuits and VTL (variable threshold logic) circuits.

However, in a logic LSI consisting of an NTL circuit, the NTL circuit does not require the reference voltage Ves. Therefore, there is no need to generate the reference voltage VBB with the internal voltage generation circuit. However, in the NTL circuit, the levels of the power supply voltage of the input stage and the power supply voltage of the emitter follower are different, and a circuit for generating the power supply voltage VEEi for the input stage is provided. And that V
As the Eei generating circuit, for example, a current extraction type voltage follower circuit 5 which requires a reference voltage VREF as shown in FIG. 3 may be used. Therefore, when using such a circuit, the internal voltage generation circuit
It is only necessary to supply the necessary reference voltage VREF to the voltage follower circuit.

In FIG. 3, reference numeral 6 indicates one of the NTL circuits that receives the voltage VEEi generated by the voltage follower circuit 5.

As explained above, the above embodiment has a path in which a constant current continues to flow regardless of fluctuations in the power supply voltage, and based on the potential on the constant current path, a constant voltage that is independent of the power supply voltage and a power supply voltage In addition to providing an internal voltage generation circuit that performs voltage compensation by generating a voltage that changes depending on Since an external control terminal is provided to enable the transistor to be controlled externally, bypass current can be injected or extracted from the constant current path in the internal voltage generation circuit depending on the external control signal. The ability to freely control the generated internal voltage makes it easier to detect defective products by forcibly reducing the operating margin when diagnosing LSIs, which greatly improves the reliability of LSIs. It has the effect of being improved.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. Nor. For example, in the above example,
Both a transistor for flowing current into the constant current path in the internal voltage generation circuit and a transistor for drawing out a part of the current are provided, but for example, regarding the generated voltage Vcs, only the margin for the increase in the power supply voltage VEE is provided. Sometimes it is enough to be able to detect it. In that case, the above transistor Q, and Q. Of these, it is possible to provide only Q1□ and omit Q2. Further, the type of the internal voltage generating circuit is not limited to that shown in FIG. 1, but can be applied to other types of circuits as well.

The above explanation will mainly focus on the bipolar logic LS, which is the application field that was the background of the invention made by the present inventor.
Although the case where the present invention is applied to I is described, the present invention is not limited thereto, and can be used in general semiconductor integrated circuits having internal voltage compensation type reference voltage generation circuits.

[Effects of the Invention] The effects obtained by typical inventions disclosed in this application are briefly explained below.

That is, in a logic LSI with a built-in voltage compensation circuit, an LSI with a small operating margin can be easily detected and reliably rejected as a defective product, thereby improving the reliability of the LSI.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment in which the present invention is applied to a bandgap reference type internal voltage generation circuit in an ECL type logic integrated circuit, and FIG. FIG. 3 is a circuit diagram showing an example of a circuit configuration when the internal voltage generating circuit is used in a logic LSI consisting of an NTL circuit. 1...Vcs control circuit, 2...Vaa control circuit, 3...ECL circuit, 4a, 4b, 5...voltage follower, 6...NTL circuit, 10...・
Internal voltage generation circuit. Figure 1 Figure 2 Figure 3 Figure 3

Claims (1)

[Scope of Claims] 1. In a semiconductor integrated circuit equipped with an internal voltage generation circuit that performs voltage compensation, at least a transistor for flowing current into a constant current path in the internal voltage generation circuit is provided, and the transistor A semiconductor integrated circuit characterized in that a control terminal is connected to an external terminal. 2. The semiconductor integrated circuit according to claim 1, further comprising a transistor for drawing out part of the current from the constant current path, and an external control terminal for the transistor. 3. The device according to claim 1 or 2, characterized in that two or more of the constant current paths are provided, and a transistor for current supply and a transistor for current extraction are provided corresponding to each of the constant current paths. Semiconductor integrated circuit.