Potential detector and semiconductor integrated circuit

Details Potential detector and semiconductor integrated circuit Potential detector and semiconductor integrated circuit

2002-10-15

2003-11-04

Cunningham, Terry D. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Specific identifiable device, circuit, or system

With specific source of supply or bias voltage

C327S566000

Reexamination Certificate

active

06642775

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a potential detector to detect an electric potential output from a high voltage generator, etc., that has reached a certain level in a semiconductor integrated circuit.
FIG. 1
shows a known potential detector
90
. The detector
90
consists of resistors R
1
and R
2
connected in series between a terminal
91
to be detected and a ground terminal V
SS
, and a comparator CMP to compare a potential at a node at which the resistors R
1
and R
2
are connected together with a reference potential Vref.
The potential at the node of the resistors R
1
and R
2
is obtained as V
1
·R
2
/(R
1
+R
2
) where V
1
is a potential at the terminal
91
. The comparator CMP outputs a high-level detection signal when the potential at the node exceeds the reference potential Vref.
The potential detector
90
is used, for example, for detecting an output potential Vout of a high voltage generator used in a semiconductor circuit such as a non-volatile semiconductor memory.
FIG. 2
shows an example where the potential detector
90
is used for detecting a potential Vout appearing at an output terminal
91
of a high voltage generator
901
such as a charge pump. The high voltage generator
901
is driven by clocks generated by an oscillator
902
such as a ring oscillator.
The potential detector
90
outputs a detection signal Dout when the potential Vout appearing at the output terminal
91
of the high voltage generator
901
reaches a certain potential to deactivate a gate
903
that has fed clocks generated by the oscillator
902
to the high voltage generator
901
. The high voltage generator
901
then stops, so that the boosted output Vout is kept at a constant level, as illustrated in FIG.
3
A.
The known potential detector generates a potential by the series-connected resistors, which is compared with a reference potential. A current always flows through the resistors R
1
and R
2
for generating the potential. The high voltage generator
901
thus requires a drive performance high enough for accepting a current consumed by the resistors R
1
and R
2
. The drive performance of the high voltage generator is decided according to the resistance of the resistors R
1
and R
2
when a load capacitance to be driven by the high voltage generator is relatively small. This requires drive performance for the high voltage generator higher than that for the high voltage generator to drive the load itself, which is not practical in view of power consumption and circuit integration.
A high voltage generator having unnecessarily high drive performance will generate a potential boosted to a high level during a response time of a potential detector. This results in a large variation in boosted output Vout against an anticipated level, as illustrated in
FIG. 3B
, with difficulty in obtaining a constantly boosted potential.
The larger the resistance of the resistors R
1
and R
2
for avoiding such potential variation, the larger the parasitic capacitance to the resistors. This results in a large delay of change in output potential of the high voltage generator, and further a large delay time required for the output potential to be transferred to the input terminal of the comparator CMP. Change in output potential of the high voltage generator illustrated in
FIG. 3C
does not have an abrupt potential increase such as shown in
FIG. 3B
, however, exhibits a slow response. This also results in unstably un-converted potential output.
SUMMARY OF THE INVENTION
A purpose of the present invention is to provide a potential detector integrated on a small area and capable of stable potential detection while consuming a small power.
Another purpose of the present invention is to provide a semiconductor integrated circuit with the potential detector and having a high voltage generator for generating a constant potential output.
The present invention provides a potential detector comprising: a first capacitor, one terminal thereof being connected to a potential detection terminal via a first switching device, another terminal thereof being connected to a reference potential terminal; a second capacitor, a terminal thereof being connected, via a second switching device, to a first node at which the first switching device and the first capacitor are connected, another terminal thereof being connected to the reference potential terminal; a third switch connected between a second node at which the second switching device and the second capacitor are connected and the reference potential terminal; a clock generator for generating clock signals to simultaneously and periodically turn on the first and the third switching devices whereas turn on the second switch periodically in an opposite timing for the first and the third switching devices; and a comparator for comparing a potential at the second node with a reference potential and outputting a detection signal when a potential at the potential detection terminal reaches a predetermined potential.
Moreover, the present invention provides a semiconductor integrated circuit having a high voltage generator for generating a boosted internal power supply potential and a potential detector for controlling the high voltage generator by detecting a potential at an output terminal of the high voltage generator, the potential detector comprising: a first capacitor, one terminal thereof being connected to an output terminal of the high voltage generator via a first switching device, another terminal thereof being connected to a reference potential terminal; a second capacitor, one terminal thereof being connected, via a second switching device, to a first node at which the first switching device and the first capacitor are connected, another terminal thereof being connected to the reference potential terminal; a third switching device connected between a second node at which the second switching device and the second capacitor are connected and the reference potential terminal; a clock generator for generating clock signals to simultaneously and periodically turn on the first and the third switching devices whereas turn on the second switching device periodically in an opposite timing for the first and the third switching devices; and a comparator for comparing a potential at the second node with a reference potential and outputting a detection signal when a potential at the potential detection terminal reaches a predetermined potential.
Furthermore, the present invention provides a semiconductor integrated circuit having a high voltage generator for generating a boosted internal power supply potential, the high voltage generator comprising: a plurality of charging circuits, each having a capacitor, one terminal thereof being connected to a high-level side power terminal via a first switching device, another terminal thereof being connected to a low-level side power terminal via a second switching device; and a plurality of third switching devices each provided between adjacent two charging circuits so that a node at which the first switching device and the capacitor of each charging circuit are connected is connected to another node at which the second switching device and the capacitor of the succeeding charging circuit are connected, wherein the capacitor of each charging circuit is charged with a potential almost equal to a power supply potential when the first and the second switching devices are turned on whereas the third switching devices are turned off and the charged capacitors of the charging circuits are coupled in series when the first and the second switching devices are turned off whereas the third switching devices are turned on, thus outputting a boosted potential.
Moreover, the present invention provides a semiconductor integrated circuit having a high voltage generator for generating a boosted internal power supply potential, the high voltage generator comprising: a charge pump having a plurality of first capacitors, adjacent two first capacitors being driven by clocks in opposite timing and a transfer

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