Adjustment circuitry in a phase-locked loop (PLL) adjusts a sampling point
to any desired location within a bit period of each bit of received
high-speed serial data. The adjustment circuitry, responsive to program
control, selectively adds current portions to a charge pump error current
output thereby adjusting a feedback signal frequency to shift the serial
data sampling point. A plurality of current mirror devices is scaled,
with respect to a reference current device, to provide .DELTA.I current
portions. A current control module controls the current portions
magnitude and a sign of the current portions. The adjustment circuitry
further controls charge pump programmable current sources in order to set
a desired operating point of the PLL. The programmable current sources
are controlled by a bias voltage and a plurality of selectable serial and
parallel coupled resistors.