Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Converting input frequency to output current or voltage
Reexamination Certificate
2000-10-20
2002-08-20
Lam, Tuan T. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Converting input frequency to output current or voltage
C327S103000, C327S589000, C327S536000
Reexamination Certificate
active
06437609
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to electronic circuits requiring a voltage higher than a low supply voltage that powers these circuits. The invention is more particularly applicable to charge pump type voltage booster circuits used in chip cards.
BACKGROUND OF THE INVENTION
An exemplary type of application of a circuit using a voltage higher than its low supply voltage is that of an integrated circuit including a non-volatile memory with floating-gate transistors. In these integrated circuits, a high voltage is needed to program and/or erase the memory. The programming and/or erasure of these memories requires a programming or erasure voltage of about 18 V, which is far higher than the low power supply voltage Vcc. The supply voltage Vcc may be about 3 V, for example. To avoid making the user provide the high voltage of 18 V, the integrated circuit is designed to have internal means for producing the high voltage from the low supply voltage Vcc. For this purpose, it is common practice to use a voltage booster circuit based upon the “charge pump” principle.
FIG. 1
a
is a schematic diagram of a known charge pump structure including a set of N series-connected elementary cells CE
1
to CEN. Each elementary cell has two input terminals E
1
and E
2
, two output terminals S
1
and S
2
, and two clock input terminals CK
1
and CK
2
. The high voltage HV is provided at the output terminal S
1
of the Nth elementary cell. The clock inputs CK
1
and CK
2
of the elementary cells CE
1
to CEN alternately receive four selection switch signals FN
1
, FN
2
, FX
1
and FX
2
produced by a control circuit
130
from a clock signal OSC. The control circuit
130
is powered by the supply voltage Vcc of the circuit. An oscillator
140
produces the clock signal OSC from the supply voltage Vcc. It is known in the art to make such an oscillator from inverters and filters. Yet, it is difficult to make a frequency-stable oscillator.
An elementary cell CE of the charge pump, illustrated in
FIG. 1
b
, includes two transistors Ta and Tb and two capacitors Ca and Cb. A terminal of the capacitor Ca, the drain of the transistor Ta, and the drain of the transistor Tb are connected together to the input terminal E
1
. Similarly, the control gate of the transistor Ta, the source of the transistor Tb, and a terminal of the capacitor Cb are connected together to the input terminal E
2
. The source of the transistor Ta and the control gate of the transistor Tb are connected respectively to the output terminals S
1
and S
2
. Finally, the other terminal of the capacitor Ca and the other terminal of the capacitor Cb are connected respectively to the clock input terminals CK
1
and CK
2
. In practice, the capacitors Ca and Cb are each made from transistors whose control gates correspond to a terminal of the capacitors and whose drains and sources, which are connected together, correspond to the other terminal of the capacitors.
The selection switch signals FN
1
, FN
2
, FX
1
and FX
2
are shown in
FIG. 1
c
. The first and third selection switch signals FN
1
and FX
1
are two complementary selection switch signals but are not overlapping in the high state. They switch between two values, which are substantially 0 and a first voltage level VA. The second and fourth selection switch signals FN
2
and FX
2
, which are not overlapping in the high state, are signals respectively synchronized with the first and third selection switch signals FN
1
, FX
1
. They switch between two values, which are substantially 0 and a second voltage value VB.
Assuming that the selection switch signals FN
1
and FN
2
are initially at VA and VB and that the selection switch signals FX
1
and FX
2
are initially at 0 V, the selection switch signals FN
1
, FN
2
, FX
1
and FX
2
are such that: the falling of the signal FN
2
to 0 V leads to the falling of the signal FN
1
to 0 V; the falling of the signal FN
1
to 0 V leads to the rising of the signal FX
1
to VA; the rising of the signal FX
1
to VA leads to the rising of the signal FX
2
to VB, which falls back to 0 V after a period of time; the falling of the signal FX
1
to 0 V leads to the rising of the signal FN
1
to VA; and the rising of the signal FN
1
to VA leads to the rising of the signal FN
2
to VB.
With the high voltage HV being obtained, the working time and the losses of the charge pump, as well as the total energy that it consumes to give the voltage HV, essentially depend on a number of factors. These factors are the number N of elementary cells, the supply voltage Vcc, and the threshold voltage VT of the transistors Ta, Tb used and the voltage levels VA, VB. Of course, it is desirable to obtain a sufficiently high voltage HV without excessively increasing the number N of elementary cells used. To do so, it is the general practice to choose a voltage level VA that is equal to the supply voltage Vcc and a voltage level VB that is as high as possible. The voltage level VB depends, inter alia, on the number N of elementary cells and on the maximum voltage to be allowed to go through the transistors TA, TB. The value of VB must be limited to not disrupt the gate oxides of the transistors. Yet, in practice, the control circuits do not provide for a voltage level VB higher than twice the supply voltage Vcc.
The problem of the total consumption of energy from the charge pump is vital particularly for applications known as contactless applications. In such application, the total energy is given remotely by a reader in the form of a radio frequency signal. The energy received by the card is limited and greatly decreases when the distance between the reader and the card increases. If it is desired to use the card at a reasonable distance from the reader, then it is necessary to limit the total energy consumption of the charge pump type voltage booster circuits used in contactless applications.
SUMMARY OF THE INVENTION
To this end, the invention proposes an integrated circuit card receiving power in the form of a radio frequency signal. The integrated circuit card may include a voltage generator that produces a first power supply voltage and a voltage booster circuit. The voltage booster circuit receives the first power supply voltage at a first supply input terminal thereof, receives a second power supply voltage higher than the first power supply voltage at a second supply input terminal thereof, and produces a high voltage.
According to one embodiment, the voltage generator may include a detection and rectifier circuit that receives the radio frequency signal and produces a rectified voltage at an output terminal thereof. A first regulator may receive the rectified voltage at a supply input terminal thereof and produce the first supply voltage. The second supply input terminal of the voltage booster circuit may be connected to the power supply input terminal of the first regulator, where the second power supply voltage is equal to the rectified voltage.
The integrated circuit card may also include a second regulator with an input terminal connected to the output terminal of the detection and rectifier circuit to receive the rectified voltage and an output terminal connected to the power input terminal of the first regulator. The second regulator receives the rectified voltage and produces the second power supply voltage, and the first regulator receives the second power supply and produces the first power supply voltage.
The voltage booster circuit may include a control circuit that produces at least one pair of selection switch signals. The first selection switch signal may oscillate between a zero voltage and a first voltage level, and the second selection switch signal may oscillate between a zero voltage and a second voltage level. The control circuit may receive the first and second power supply voltages. Also, the first and second voltage levels may be obtained respectively from the first and second power supply voltages.
The voltage booster circuit may further include N series-connected elementary cells for producing the high voltage. The N elementary
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Jorgenson Lisa K.
Lam Tuan T.
Nguyen Hiep
STMicroelectronics S.A.
LandOfFree
Charge pump type voltage booster circuit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Charge pump type voltage booster circuit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Charge pump type voltage booster circuit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2930880