Static information storage and retrieval – Read/write circuit – Including reference or bias voltage generator
Reexamination Certificate
2000-11-10
2001-11-20
Mai, Son (Department: 2818)
Static information storage and retrieval
Read/write circuit
Including reference or bias voltage generator
C365S226000, C327S538000, C327S543000
Reexamination Certificate
active
06320796
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to charge pump circuits, and in particular to charge pump circuits that provide a regulated output voltage.
2. Discussion of the Related Art
A charge pump circuit is generally used for boosting a power supply voltage to a higher voltage level to be used for powering ancillary circuits. Closed loop control is sometimes used with charge pumps to provide a regulated output voltage. However, charge pumps that include closed loop control typically have extremely slow response times due to the relatively small amount of energy that can be transferred during each clock cycle. Exacerbating the slow response times is the effect of inherent leakage currents that occur within the charge pump. When diodes within the charge pump are back biased, a small but significant leakage current flows backwards through the diode. The leakage current transfers charge out of the output storage devices back to the voltage supply, causing the output voltage to slowly decrease. The output voltage continues to decrease until the output controller detects an error of sufficient magnitude between the output voltage and the voltage reference. The controller then enables several cycles of energy to be transferred to the output storage devices. However, due to the slow response of the controller, the output voltage will typically overshoot slightly. Then, the cycle of leakage current, decreasing output voltage, slow response controller starts anew. The steady-state effect is a low-magnitude, low-frequency oscillation occurring on the output voltage that is somewhat related to the magnitude of the leakage current. Compensating for the effect of leakage currents prior to manufacturing is problematic, since the magnitude of leakage currents are dependent on several factors including the semiconductor manufacturing process, die defects, and temperature.
SUMMARY OF THE INVENTION
The present invention provides a circuit and method for generating a regulated voltage from a first voltage of a first voltage source. The circuit includes a driver for generating a drive signal. A charge pump is coupled to the driver for generating a pump voltage from the first voltage source. The charge pump generates the pump voltage in response to the drive signal. The charge pump includes at least two charging modes. An amplifier has a reference input coupled to a reference voltage, and a sense input coupled to a sense signal representative of the pump voltage. In response to a difference between the reference voltage and the sense signal, the amplifier generates an output to control the driver. A pump controller is coupled from the amplifier output to the charge pump. The pump controller includes a measuring device that is operable in response to a mode criteria, to select a charging mode of the charge pump.
For a more complete understanding of the invention, its objects and advantages, reference may be had to the following specification and to the accompanying drawings.
REFERENCES:
patent: 4527180 (1985-07-01), Oto
patent: 6107862 (2000-08-01), Mukainakano et al.
patent: 6107864 (2000-08-01), Fukushima et al.
patent: 6191994 (2001-02-01), Ooishi
Sutardia Sehat
Voo Thart Fah
Harness & Dickey & Pierce P.L.C.
Mai Son
Marvell International Ltd.
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