JPH03162129A - semiconductor integrated device - Google Patents

Abstract

PURPOSE:To decrease the current noise and to prevent the occurrence of a malfunction of a circuit by providing a feedback circuit for operating a bypass circuit for stopping a function for limiting a current to an output driver by a variation of an output. CONSTITUTION:An output circuit of a semiconductor integrated circuit is constituted of NPN bipolar output drivers 1, 3, a diode 2, resistances 4, 11, current limiting circuits 5, 8, bypass circuits 6, 9, and output feedback circuit 7, 10. In this output circuit, a current of the output drivers 1, 3 is limited in the beginning of an operation, and this limit is released by receiving a variation of an output signal. In such a way, the maximum current value and a time variation rate of a current can be made small, and by reducing the voltage fluctuation of a power source line, a malfunction of the circuit can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an output circuit for a semiconductor integrated device, and more particularly to an output circuit that reduces current noise generated in a power supply line during data output. [Prior art 1] Figure 5 is a diagram showing a CMOS output circuit of a conventional semiconductor integrated device. 14 is the P-channel MOSFET output driver. 12 is its drive circuit. 15 is an output driver of the N-channel MOSFET, and 13 is its driving circuit. Input DIN. 14 when both DINs are low level
．． 15 is off and the output terminal D out is in a high impedance state. FIG. 6 is a diagram of operating waveforms of the output circuit of FIG. 5, and shows the case where D out falls. DIN
When becomes high level, the gate voltage V an of the N-channel driver changes from Ov to ■. . The current of the N-channel driver reaches its peak and discharges the charge at the output terminal. As the voltage of Dout decreases, the current decreases. D. When ut rises, DIN becomes high level, Vap becomes 0, and the output terminal is charged through the P channel driver. [Problem to be solved by the invention 1] As semiconductor technology advances, semiconductor integrated devices are becoming faster and more highly integrated. In order to increase the operating speed of output circuits, output drivers with large current driving power are used in order to increase the operating speed of output circuits, and as the degree of integration increases, semiconductor integrated devices are beginning to have many output terminals. As speed increases and integration increases, a large amount of transient current flows when the output circuit operates, and the voltage of the power supply line due to parasitic resistance or inductance existing in the wiring inside the integrated device, the lead frame, and the external wiring. fluctuates, causing circuit malfunction. When the output driver of a conventional output circuit starts operating, its current driving power reaches its maximum, and a large current suddenly flows through the power supply line, causing large current noise to be concentrated in a short period of time, causing circuit malfunction. It is the cause.

The above phenomenon is particularly noticeable when the output driver is formed from a bipolar transistor with low on-resistance. The present invention has been made to solve these problems, and therefore, it is an object of the present invention to provide a semiconductor integrated device that reduces peak current and the time rate of change of current, that is, current noise, and does not cause circuit malfunction. .

[Means for Solving the Problems 1] The semiconductor integrated device of the present invention has a current limiter that limits the base current supplied to the output driver in an output driver drive circuit that provides drive current to a bipolar output driver formed in a totem pole. The present invention is characterized in that it includes a circuit, a bypass circuit connected in parallel with the current limiting circuit to stop the current limiting function, and a feedback circuit that operates the bypass circuit according to a change in output.

[Example〕 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an output circuit according to an embodiment of the present invention. The drive circuit for the NPN bipolar transistor 1 includes a current limiting circuit 5 in which a diode and a P-channel MOSFET are connected in series, and a bypass circuit 6 using a P-channel MOSFET, where 6 is the voltage of the previous stage. Delay after changes? The operation is controlled by the output signal of the feedback circuit 7 from D6ut. Figure 2 shows the feedback circuit 7. In this embodiment, in order to prevent short-circuit current in NPN bipolar transistors 1 and 3, logic is established with the D++i signal. D again. Since the bypass circuit 6 is turned ON in response to the rise of , the ON timing of the bypass circuit 6 can be changed by changing the logic level of the inverter shown in FIG. Also NP
The drive circuit for the N bipolar transistor 3 includes a current limiting circuit 8 in which a diode and a P-channel MOSFET are connected in series, and a bypass circuit 9 using a P-channel MOSFET. The operation is controlled by the output signal of the feedback circuit 10 from D out. Figure 3 shows the feedback circuit 10. In this embodiment, NPN bipolar transistors 1 and 3
It is logically connected to the DIN signal to prevent short-circuit current. Also D. In response to the falling of ■, the bypass circuit 9 is turned to O.
Since it is designed to be N, the negative AND in Figure 3
bypass circuit 9 by changing the logic level of
The ON timing of can be changed. Next, we will explain the operation of the circuit in Figure 1 based on the waveforms in Figure 4. *When DIN goes to L level, V0 in Figure 1 rises and passes through 5 to V
The voltage at 6a increases.

Here, ■1 is still at H level, so 6 is off and Al.
Therefore V. becomes VD0VBt. V0. When v1 becomes L level after a delay time △t due to 7 due to the change from L level to intermediate potential, 6 turns on and rises again to approximately V
Reach 0. At this time, the current flowing through the current limiting circuit 5 becomes almost zero. Therefore, by controlling the base voltage of the NPN bipolar transistor as described above, the current flowing through l can be limited. In other words, the current flowing through l is v. 7! +5VoIll-v. E notokiha I1
Te is limited and V0. When , peak current I2 flows.
Therefore, the peak current of the output driver 1 is suppressed, and at the same time, the time rate of change of the current is reduced. When D IN falls and the output D out falls, V ab is initially V. ．． −
■． Vout is reached after Δt. 3
The current flowing through is divided into stages ■ and I, as shown in Figure 4. [Effects of the Invention] As described above, the output circuit of the present invention limits the current of the output driver at the initial stage of operation, and releases the above limitation in response to a change in the output signal. This has the effect of reducing voltage fluctuations in the power supply line and preventing circuit malfunctions.

[Brief explanation of the drawing]

1 is an output circuit diagram showing one embodiment of the present invention, FIG. 2 is a diagram showing an example of the output feedback circuit 7 of FIG. 1, and FIG. 3 is a diagram showing an example of the output feedback circuit 7 of FIG.
A diagram showing an example of the output feedback circuit 10 in the figure, FIG.
A diagram showing the operating waveforms in the figure. Figure 5 shows a conventional output circuit. Figure 6 is a diagram showing the operating waveforms of Figure 5. 1, 3...NPN bipolar output dryer 2, 4, 5, 6, 7, 1 4, l 5, l 2, DIN, D. ．． , V da) V ap, VO ・ ■1 , 1 3 ・ D1.4・ v,! 1. Vdll・ ■１ ■, ・Diode・Resistor・Current limit circuit・Bypass circuit・Output feedback circuit・P channel output driver・N channel output driver・Drive circuit・Output circuit complementary input signal・Output circuit output signal・Output driver drive Signal voltage: Current control circuit input signal voltage: Pibus circuit input signal voltage or higher

Claims (1)

[Claims] In an output driver drive circuit that supplies drive current to a bipolar output driver formed in a totem pole, there is a current limit circuit that limits the base current supplied to the output driver, and a current limit circuit that is connected in parallel with the current limit circuit to stop the current limit function. 1. A semiconductor integrated device comprising: a bypass circuit that operates the bypass circuit; and a feedback circuit that operates the bypass circuit based on a change in output.