JP2000346909A - Internal voltage monitoring circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the reliability of an internal voltage monitoring circuit by comparing a reference voltage which is provided at the outside with an internal voltage and obtaining a linear value. SOLUTION: A power supply voltage 21 and a resistance division part 22 are connected to a comparator 24. The comparator 24 is connected to a reference voltage 23 from the outside of a microprocessor, and it is connected to a multiplexer 25. A value which changes the reference voltage 23 at the outside and which is compared with an internal voltage by the comparator 24 can select the voltage of an element which is to be monitored by the control signal of the multiplexer 25. Each voltage is outputted as a linear value. When it is compared with the internal voltage by the comparator 24, an error which is caused by an external noise or the like can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for monitoring an internal voltage used in a microprocessor or the like.

[0002]

2. Description of the Related Art Recently, to reduce power consumption and the like, one
In an LSI, it is common practice to operate each circuit at a different power supply voltage. At this time, there is a method of supplying each power supply voltage from the outside of the LSI. However, in order to reduce the number of external terminals, a method of generating another power supply voltage from one externally supplied power supply voltage is widely used.

When such a method is adopted, it is monitored during an inspection or the like whether an intended power supply voltage is generated accurately.

FIG. 1 is a schematic diagram of a circuit for monitoring the internal voltage of a conventional microprocessor. In the figure, a power supply voltage 11 is a power supply voltage applied from the outside of the microprocessor, and a resistance division 12 is used by the resistance division 12 in order to use a power supply voltage or a boosted voltage in the internal circuit 1, the internal circuit 2, and the like. This indicates that partial pressure is applied. Further, it indicates that the memory cell 13 monitors a voltage at the time of writing, a voltage at the time of erasing, or a voltage at the time of reading. The value of the memory cell is determined by a digital value via a sense amplifier.

The conventional internal voltage monitoring circuit having the above configuration is configured to directly monitor the internal voltage to be selected at the external output terminal 14 when monitoring the internal voltage to be selected.

[0006]

In the internal voltage monitor circuit, it is required that the measured internal voltage does not change due to noise or the like. However, in the conventional internal voltage monitor circuit shown in FIG. 1, an output terminal 14 is provided outside to monitor the internal voltage. In this method, there is a possibility that an erroneous determination is made due to an external factor such as noise from the output terminal 14.

Further, even when an internal A / D converter is used, an accurate value cannot be measured because the output voltage is limited by the A / D bit precision.

The present invention has been made in consideration of the above problems, and has as its object to improve the reliability without erroneous determination due to the influence of noise or the like.

[0009]

In order to solve this problem, an internal voltage monitor circuit according to the present invention includes an external reference voltage for measuring a divided voltage, a boosted voltage of a power supply voltage, and a memory cell voltage. A linear value is obtained by comparing the reference voltage and the internal voltage.

[0010]

(Embodiment 1) FIG. 2 is a configuration diagram of an embodiment of an internal voltage monitor circuit of the present invention. The embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 2, a power supply voltage 21, which is a component of the microprocessor, and a resistor divider 22 for dividing the power supply voltage 21 for use in the internal circuit 1, the internal circuit 2 and the like are shown. Also shown are a reference voltage 23 applied from outside the microprocessor, an element to be monitored, a comparator 24 for comparing with the external reference voltage 23, and a multiplexer 25 for selecting a compared value.

The power supply voltage 21 and the resistor divider 22 are connected to a comparator 24. Power supply voltage 21 and resistance divider 22
Are connected to a reference voltage 23 from outside the microprocessor, and the connected comparators 24 are connected to a multiplexer 25. The value obtained by changing the external reference voltage 23 and comparing with the comparator 24 can select the voltage of the element to be monitored by the control signal 26 of the multiplexer 25. Each voltage value is output as a linear value, and by comparing with the comparator 24, an error due to a factor such as external noise is suppressed.

When the internal voltage is not monitored, the external reference voltage 23 can be cut off by the control signal of the tri-state buffer 27.

(Embodiment 2) FIG. 3 is a block diagram of an embodiment of an internal voltage monitor circuit of the present invention. The embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows a memory cell 31 constituting a flash memory. Further, a reference voltage 32 applied from outside the microprocessor and a memory cell 31 to be monitored are connected to a comparator 33 which compares the voltage with the gate, source and drain, and the comparator 33 sends a signal to a multiplexer 34 for selecting a compared value. Connected. The value obtained by changing the external reference voltage 32 and comparing with the comparator 33 can select the voltage of the memory cell to be monitored by the control signal 35 of the multiplexer 34. Each voltage value is output as a linear value, and by comparing with the comparator 33, an error due to a factor such as external noise is suppressed.

When not monitoring the internal voltage, the external reference voltage 32 can be cut off by the control signal of the tri-state buffer 36.

[0017]

As described above, the internal voltage monitor circuit of the present invention can operate the CPU in accordance with the instruction of the microprocessor, arbitrarily select the element whose internal voltage is to be monitored using the multiplexer, and use the comparator to control the external voltage. By providing a comparison with a reference voltage, it is possible to provide a product that can accurately and linearly measure an internal voltage (voltage division, boosting of a power supply voltage, and a memory cell voltage) and that does not malfunction due to external noise or the like.

[Brief description of the drawings]

FIG. 1 is a block diagram of a microprocessor including a conventional internal voltage monitor circuit.

FIG. 2 is a block diagram of a microprocessor including an internal voltage monitor circuit of the present invention.

FIG. 3 is a block diagram of a microprocessor including an internal voltage monitor circuit according to the present invention.

[Explanation of symbols]

 Reference Signs List 21 power supply voltage 22 resistance division 23 reference voltage 24 comparator 25 multiplexer 26 control signal 27 tri-state buffer 31 memory cell 32 reference voltage 33 comparator 34 multiplexer 35 control signal 36 tri-state buffer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G032 AA03 AB19 AC03 AD01 AK14 AK15 AL05 5F038 BB05 BG03 BH19 DF04 DF06 DT12 EZ20

Claims (2)

[Claims] A comparator is provided inside a microprocessor, an element whose voltage is to be monitored is connected to the comparator, and a reference voltage is connected to the comparator connected to the element whose voltage is to be monitored from outside the microprocessor. An internal voltage monitor circuit which changes a voltage value of a reference voltage and monitors a linear value which is compared with the comparator. 2. A comparator is provided inside a microprocessor, a plurality of elements to be monitored for voltage are connected to the comparator, and a reference voltage is connected to the comparator connected to the element to be monitored for voltage from outside the microprocessor. Changing the voltage value of the reference voltage, connecting a linear value that is compared with the comparator to a multiplexer, and selecting an element whose voltage is to be monitored by the multiplexer from a plurality of elements whose voltage is to be monitored. Internal voltage monitor circuit.