High-Gain PFD/Charge Pump with Gain Proportional to Slew Rate of Up/Down Signals

A high-gain low-noise phase-frequency detector/charge pump (PFD/CP) topology is proposed. When input phase error is small, as in the locked state, the charge pump achieves a high linear gain and works without being fully turned on. When input phase error is large, as in acquisition state, the CP gain drops to Icp/2 $\pi$ as with conventional tri-state charge pumps. In simulation the prototype high-gain charge pump demonstrates a gain of 10x higher than that of a conventional charge pump with an input range of +/-100pS. A charge-pump contributed in-band noise floor of -116dBc/Hz is achieved, which is 18dB lower than that of a conventional PFD/CP with the same bias current of 40uA, in a PLL with 4GHz output frequency and 50MHz reference frequency.