| 摘要 |
PURPOSE:To prevent production of noise by devising this charge pump circuit such that when one of two output terminals of the charge pump supplies a current to an external circuit, the other output terminal draws a current so as to prevent current flowing to a neutral point between loop filter capacitors. CONSTITUTION:With a terminal In1 set to logic '1' and a terminal In2 set to logic '0', n-channel MOSs Qn1, Qn4 and p-channel MOSs Qp2, Qp3 are conductive. In this case, the output current of a MOS Qp7 entirely flows to the drain of a MOS Qn6 via parallel circuit comprising the MOS Qn1, Qp3. The output of a MOS Qp6 is fed to the output terminal Out1 via the MOS Qp2 and the output current of a MOS Qn7 is fed to the output terminal Out2 via the Qn4, resulting that the terminal Out 1 supplies a current while the 2nd output terminal Out2 draws a current. With the terminal In2 only set to logic '1', the terminal Out1 draws a current. When the absolute value of the current which is supplied or drawn is set identical to each other, the currents flowing to capacitors C1, C2 are equal to each other and no current flows to a bias voltage input terminal VB2. |
