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This paper proposes a time-residue feedback scheme to balance resolution and complexity in a cell-based time-to-digital converter (TDC). The time residue is amplified and fed back into a cyclic-ring Vernier recursively until it cannot be detected correctly. Only one variable-resolution cyclic-ring Vernier and one tunable delay-chain time amplifier (TA) are adopted. Both coarse and fine oscillators of the proposed Vernier which are designed by the same variable-resolution digital controlled oscillator can be switched off to decrease ground bounce during TA activities. With various control codes, the TDC resolution is also programmable. The test application-specified integrated circuit which has a 13-b resolution and occupies 0.02 mm2 in TSMC 65-nm CMOS process can operate in either feedback or feedforward mode. In feedback mode, the measurements of sampling rate, resolution, input range, differential nonlinearity, and integral nonlinearity are 10 MHz, 0.98 ps, 5.76 ns, ± 0.8 LSB, and ± 2.2 LSB, respectively; it also consumes 3 mW at 1 V supply voltage. The sampling rate, resolution, and power dissipation of the feedforward operation are 250 MHz, 6.01 ps, and 17.5 mW, respectively.

This paper presents an all-digital standard cell SR-Latch based time amplifier (TA) with a variable gain of 6X and 12X. In this TA, a two-stage gain selection unit is applied to enable the TA to select either the high gain for short input pulse intervals or the low gain for long input pulse intervals. The time amplification gain is 6 in the input range of −700ps ∼700ps, and reaches 12 if the input range is −300∼300ps. We present a design that automatically detects the input pulse and switches to the proper TA gain. By applying the proposed TA, a standard cyclic TDC implemented in a UMC CMOS 65-nm process shows the resolution improved from 1.6ps to 0.8 ps.

This paper presents an all-digital delay-locked loop with the novel digital delay line for high-speed memory interface applications. The proposed digital delay line has smaller tuning step and better tuning linearity than the prior arts. The proposed ADDLL inside the DDR3 PHY for the purpose of the 90-degree phase shift and read leveling is fabricated in a 40nm low-power CMOS process. The testchip is successfully verified at the data rate of 800∼1600Mbps. The measured peak-to-peak and rms jitter of the write DQS are 60ps and 10ps at the data rate of 1600Mbps, respectively.