from the C4 bumps. The PLL uses a proportional and integral
control compensation scheme. The current-controlled oscillator
has relatively low swing, so it needs a level shifter to convert
its swing to full rail. Apart from the two dividers D3 and D4,
all components of PLL use the VREG supply to improve power
supply rejection. D3 and D4 use the 1.1 V digital supply. The
voltage-controlled oscillator (VCO) is composed of a V/I con-
verter, a current-controlled oscillator, and a level shifter.