Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
2002-12-12
2004-09-14
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
C363S059000
Reexamination Certificate
active
06791395
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to a boost circuit, and more particularly to, a boost circuit capable of constantly maintaining a pumping voltage regardless of variation in a power supply voltage.
2. Description of the Prior Art
In order to improve the level of integration and lower power consumption, a research on circuits that operates at a low operating voltage has recently been made actively. In order for the device to operate, a voltage higher than the power supply voltage (Vcc) is required as the operating voltage, if necessary. To this end, it is required that the power supply voltage be boosted to a target voltage. A boost circuit is a circuit for boosting the power supply voltage to the target voltage.
A construction of a conventional boost circuit will be described by reference to FIG.
1
.
FIG. 1
is a circuit diagram of the conventional boost circuit for explaining the construction and operation of the boost circuit.
The boost circuit includes a pumping capacitor C
101
, a precharge unit
110
, a voltage dividing unit
120
and a kick signal generating unit
130
.
The pumping capacitor C
101
is connected between a first node N
101
being an output node and a second node N
102
. The precharge unit
110
serves to apply the precharge voltage of the pumping capacitor C
101
to the first and second nodes N
101
and N
102
according to a non-inverted pumping signal (BOOST). The voltage dividing unit
120
is connected between the second node N
102
and a ground voltage (Vss) terminal and generates a divided voltage (VBREF). The kick signal generating unit
130
compares the divided voltage (VBREF) from the voltage dividing unit
120
with the reference voltage (VREF) and also applies the kick signal (VKICK) to the second node N
102
according to the inverted pumping signal (BOOSTB) to boost the voltage of the first node N
101
to the pumping voltage (VBOOST). A load capacitor C
102
is connected between the first node N
101
being the output node and the ground voltage (Vss) terminal.
In the above, the precharge unit
110
is connected between the power supply voltage (Vcc) terminal and the first node N
101
. The precharge unit
110
includes a first switching means P
101
driven by the inverted pumping signal (BOOST), an inverting means L
101
for inverting the non-inverted pumping signal (BOOST), and a second switching means N
101
connected between the second node N
102
and the ground voltage (Vss) terminal and driven by the output signal of the inverting means L
101
. At this time, the first switching means P
101
may be implemented using a PMOS transistor, the second switching means N
101
may be implemented using a NMOS transistor and the inverting means L
101
may be implemented using an inverter.
Further, the voltage dividing unit
120
includes a plurality of resistors (only two first and second resistors are shown in the drawing, R
121
and R
122
) serially connected between the second node N
102
and the ground voltage (Vss) terminal. The plurality of the resistor R
121
and R
122
divide the voltage of the second node N
102
to generate the divided voltage (VBREF).
Meanwhile, the kick signal generating unit
130
includes a switching means P
131
connected between the power supply voltage (Vcc) terminal and the second node N
102
, for switching the power supply voltage (Vcc), a comparator
131
for comparing the divided voltage (VBREF) and the reference voltage (VREF), and a driving unit
132
to which the inverted pumping signal (BOOSTB) is applied as an enable signal, for driving the switching means P
131
so that the kick signal (VKICK) is applied to the second node N
102
according to the output signal of the comparator
131
. At this time, the switching means P
131
may be implemented using a PMOS transistor. The driving unit
132
includes a NOR gate device L
131
having two inputted to which the inverted pumping signal BOOSTB) and the output signal of the comparator
131
are inputted, respectively, and an inverter L
132
for inverting the output signal of the NOR gate device L
131
to generate the driving signal (KICKB) of the switching means P
131
.
FIG. 2
is a graph illustrating the signal applied to the boost circuit in
FIG. 1 and a
waveform of a specific node. The operation of the conventional boost circuit will be described by reference to FIG.
1
and FIG.
2
.
At a precharge period (A) in which the pumping signal (BOOST) is applied as a LOW level, the first switching means P
101
is turned on by the pumping signal (BOOST) and the second switching means N
101
is simultaneously turned on by the inverted pumping signal (BOOSTB) through the inverting means L
101
. Also, the inverted pumping signal (BOOSTB) is applied to the kick signal generating unit
130
to disable the kick signal generating unit
130
. In more detail, the inverted pumping signal (BOOSTB) is also applied to the NOR gate device L
131
included in the driving unit
131
of the kick signal generating unit
130
. If the inverted pumping signal (BOOSTB) is applied, the NOR gate device L
131
of the driving unit
131
generates a signal of a LOW level. This signal is then inverted by the inverting means L
132
. As the switching means P
131
is turned of by the output signal (KICKB) of the inverting means L
132
, the power supply voltage (Vcc) is not applied to the second node N
102
. Therefore, the power supply voltage (Vcc) is transferred to the first node N
101
and the ground voltage (Vss) is also transferred to the second node N
102
, through the first switching means P
101
and the second switching means N
101
that are turned on, so that the pumping capacitor C
101
is precharged. At this time, the voltage dividing unit
120
outputs the divided voltage (VBREF) as the ground voltage (Vss) by the ground voltage (Vss) transferred to the second node N
102
.
Next, in a pumping period (B) in which the pumping signal (BOOST) is applied as a HIGH level, the first switching means P
101
is turned off by the pumping signal (BOOST). The second switching means N
101
is simultaneously turned off by the inverted pumping signal (BOOSTB) through the inverting means L
101
.
Meanwhile, the comparator
131
of the kick signal generating unit
130
compares the divided voltage (VBREF) being the ground voltage (Vss) and the reference voltage (VREF) to generate a signal of a LOW level. This signal is then is applied to the NOR gate device L
131
along with the inverted pumping signal (BOOSTB) of the LOW level, so that the NOR gate device L
131
generates a signal of a HIGH level. Next, the signal of the HIGH level of the NOR gate device L
131
is applied to the switching means P
131
as the signal (KICKB) inverted by the inverting means L
132
, so that the switching means P
131
is turned on. The power supply voltage (Vcc) is applied to the second node N
102
through the switching means P
131
that is turned on, and the voltage of the first node N
101
is simultaneously boosted to the pumping voltage (VBOOST) by the pumping capacitor C
101
of the precharge state. At this time, in an initial period (Bb) of the pumping period (B), a little distortion occurs in the kick signal (VKICK) as the comparator
131
compares the divided voltage (VBREF) and the reference voltage (VREF). However, this distortion is stabilized soon.
Through the above operation, the pumping voltage (VBOOST) higher than the power supply voltage (Vcc) is generated. The pumping voltage (VBOOST) is supplied to a device requiring a high voltage as the operating voltage.
In the above boost circuit, the power supply voltage (Vcc) is used as the precharge voltage of a positive voltage. If the power supply voltage (Vcc) is increased, the amount of the precharge voltage is accordingly increased. Thus, the pumping voltage (VBOOST) is generated as a voltage higher than a target voltage. As such, if the pumping voltage (VBOOST) is generated as the voltage higher than the target voltage, the device is overworked and the device may be damaged.
Therefore, in order to prevent this, t
Cunningham Terry D.
Hynix Semiconductor Inc
Jacobson & Holman PLLC
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