Sanyo Electric Co., Ltd.

Yoshitaka Onaya

Takeo Inoue

Takao Myono

Hideki Ohashi

Tatsuya Suzuki

An echo prevention circuit includes a filter that receives a first digital signal and outputs second and third digital signals; first and second DA converter that convert the second and third digital signals into first and second analog signals respectively; a circuit to subtract the second analog signal from a signal generated by combining the first analog signal and a third analog signal, a circuit to amplify the signal from the subtracting circuit; an AD converter that converts the amplified signal into a digital signal; a responsive signal acquiring unit to acquire a first response signal from the input of the first DA converter to the output of the AD converter and to acquire a second response signal from the input of the second DA converter to the output of the AD converter; and a unit to set filter coefficients based on the first and second response signals.

Echo prevention circuit, filter coefficient setting method, and recording medium with program recorded

A size of a charge pump circuit is reduced as well as its cost. In a positive booster charge pump circuit in an embodiment of this invention, a positive boosted voltage 2VDD generated at its first stage node is used as a gate voltage to turn on a MOS transistor that outputs a high level (VDD) of each of the first, third and fourth clock drivers. And in a negative charge pump circuit, a negative boosted voltage &#x2212;VDD generated at its first stage node is used as a gate voltage to turn on a MOS transistor that outputs a high level of each of the second and fifth clock drivers.

Charge pump circuit

An inrush current at beginning of operation of a charge pump circuit is reduced to prevent adverse effect on other circuits in a system. Charge transfer MOS transistors are connected in series. One end of each coupling capacitor is connected to each connecting point of the charge transfer MOS transistors. An output from each clock driver is applied on the other end of the respective coupling capacitor. Each clock driver includes a first clock driver and a second clock driver having higher driving capacity than the first clock driver. Each clock driver is controlled so that the first clock driver is put into operation at first and at the end of a predetermined elapsed time it is stopped and the second clock driver is put into operation.

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Ota, Japan

Yoshitaka Onaya