Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – With rotor
Reexamination Certificate
2003-03-28
2004-10-05
Zarneke, David A. (Department: 2829)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
With rotor
C324S765010, C324S762010, C323S282000
Reexamination Certificate
active
06801033
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a semiconductor integrated capable of increasing drive performance by changing a substrate potential of a MOS transistor (back gate voltage) when a NOS transistor is employed as an output transistor of a voltage converter such as a voltage regulator (referred to herein as a V/R circuit) in an integrated circuit, a charge pump circuit (hereinafter referred to as CP circuit), or a switching element (hereinafter referred to as SW element) of a switching regulator.
2. Description of Related Art
Voltage regulators outputting a related positive voltage such as shown in the circuit diagram of
FIG. 9
are well-known. Namely, a related voltage regulator comprises a voltage regulator control circuit consisting of an error amplifier
13
for amplifying a difference voltage for a reference voltage Vref of a reference voltage circuit
10
and a voltage of a connection point of bleeder resistors
11
,
12
dividing a voltage Vout (referred to as output voltage in the following) of a voltage regulator output terminal
5
, and an output transistor
14
. A positive power supply voltage VDD is applied to a power supply voltage terminal
15
.
If an output voltage of the error amplifier
13
is taken to be Verr, an output voltage of the reference voltage circuit
10
is taken to be Vref, and a voltage of a connection point of the bleeder resistors
11
,
12
is taken to be Va, then, if Vref>Va, Verr becomes low, while conversely, if Vref<Va, then Verr becomes high.
The output transistor
14
is a p-channel MOS transistor in this case. Therefore, when Verr becomes low, the voltage across the gate and source becomes large, the on resistance becomes small and operation is such that the output voltage Vout is caused to rise. Conversely, when Verr goes high, operation is such that the on resistance of the output transistor
14
goes high, and the output voltage goes low, so that the output voltage Vout is kept at a fixed value.
An ON resistance Ron of the output transistor
14
constitutes a function for the voltage Vgs between the gate and source and a transistor threshold voltage Vt, with the ON resistance of the transistor being smaller than Vgs−Vt. Typically, the ON resistance for the region where the voltage across the drain and source of the transistor is small is given by the equation (1).
Ron
=
1
μ
·
Cox
·
W
/
L
·
(
Vgs
-
Vt
)
(
1
)
Here, &mgr; is mobility, Cox is gate capacitance per unit surface area, W is transistor gate width, and L is gate length.
It is necessary to increase the gate width W of the transistor in order to lower the ON resistance of the output transistor. This increases the surface area of the IC and therefore causes costs to increase.
On the other hand, voltage regulators of the related art outputting a negative voltage, such as shown in the circuit diagram of
FIG. 10
, are well-known. Namely, a related voltage regulator comprises a voltage regulator control circuit consisting of an error amplifier
13
for amplifying a difference voltage for a reference voltage of a reference voltage circuit
10
and a voltage of a connection point of bleeder resistors
11
,
12
dividing a voltage−Vout of a voltage regulator output terminal
5
, and an output transistor
17
. A negative power supply voltage−VSS is applied to a power supply voltage terminal
16
. If an output voltage of the error amplifier
13
is taken to be −Verr, an output voltage of the reference voltage circuit
10
is taken to be −Vref, and a voltage of a connection point of the bleeder resistors
11
,
12
is taken to be −Va, then, if −Vref<−Va, −Verr becomes low (approaches −VSS), while conversely, if −Vref>−Va, then −Verr becomes high (approaches GND).
An output transistor
17
is an N-channel MOS transistor in this case. Therefore, when −Verr becomes high, the voltage across the gate and source becomes large, the ON resistance becomes small and operation is such that the output voltage Vout is caused to fall. Conversely, when −Verr goes low, operation is such that the ON resistance of the output transistor
17
goes high, and the output voltage goes high, so that the output voltage Vout is kept at a fixed value.
As with the positive voltage regulator, it is necessary to increase the gate width W of the output transistor in order to lower the on resistance of the output transistor, with the on resistance of the output transistor being given by equation (1). This increases the surface area of the IC and therefore causes costs to increase.
A configuration for a circuit taken as a related booster-type SW regulator is shown in FIG.
11
.
An input power supply
120
is connected to a coil
121
and a power supply terminal
101
of an SW regulator control circuit
130
. The other end of the coil
121
is connected to a drain of an SW element
122
and an anode of a commutation diode
123
. A cathode of the diode
123
is connected to an output voltage terminal
102
of the SW regulator, and a capacitor
124
and a load
125
are connected to the output voltage terminal
102
. If a voltage of an output voltage terminal
102
is taken to be Vout, the SW regulator control circuit
130
controls the SW element
122
to be on or off in such a manner that Vout is fixed. The gate of the SW terminal
122
is connected to the terminal
103
of the drive circuit
131
of the SW element, and the SW element
122
is made to go on and of f as a result of being driven by the voltage Vext of the terminal
103
. In
FIG. 11
, the SW element
122
is an N-channel MOS transistor. The voltage Vext of the output terminal
103
of the drive circuit
131
is outputted as a positive voltage “H” in order to put the SW element
122
on, and is outputted as a GND level voltage in order to put the SW element
122
off. The source and substrate of the SW element
122
are both connected to GND.
Generally, it is preferable for the electrical power conversion efficiency of the SW regulator circuit to be high. It is necessary for the electrical power conversion efficiency to be high in order to reduce loss due to on resistance when the SW element
122
is on. If current flowing in the SW element
122
is taken to be I, and on resistance of the SW element is taken to be Ron, then loss Pron when the SW element
122
is on is given by:
Pron=IxIxRon (2)
i.e., it is necessary to lower the on resistance of the SW element in order to make the loss Pron of the SW element small. Typically, the on resistance for the region where the voltage across the drain and source of the MOS transistor is small is given by equation (1) described previously.
It is necessary to increase the gate width W of the transistor in order to lower the on resistance of the MOS transistor. This increases the surface area of the IC and therefore causes costs to increase. Making the gate width W large also increases the capacitance of the gate of the. MOS transistor so that loss when charging and discharging the gate capacitance of the MOS transistor when turning the MOS transistor on and off is also increased. The surface area of the drive circuit itself also increases in order to drive this large capacitance.
The configuration of a circuit shown in
FIG. 12
is given as an example of a related double-boosting-type circuit. The positive side of a power supply
220
of the input of
FIG. 12
is connected to switch elements
221
and
224
, and the negative side of the power supply
220
is connected to the SW terminal
222
. A capacitor
225
and SW element
223
are connected to the other end of the SW element
221
, with a SW element
224
being connected to the other end of the capacitor
225
. A capacitor
226
and load
227
are connected to the other end of the SW element
223
. The switch elements
221
to
224
are controlled to go on and off by a signal from a CP control circuit
228
.
The switch elements
221
and
222
, and
223
and
224
go
Osanai Jun
Sudo Minoru
Adams & Wilks
Seiko Instruments Inc.
Tang Minh N.
Zarneke David A.
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