Masaya Kibune

Split capacitor DAC mismatch calibration in successive approximation ADC

A split capacitor DAC calibration method is proposed that a bridge capacitor larger than conventional design allows a tunable capacitor to compensate for mismatch. To guarantee proper calibration, a comparator with digital timing control offset cancellation is proposed. An 8-bit successive approximation ADC with 4b+4b split capacitor DAC calibration has been implemented in 65nm CMOS, achieving 0.3LSB DNL and INL with 180fF input capacitance.

A CMOS multichannel 10-Gb/s transceiver

We describe a CMOS multichannel transceiver that transmits and receives 10 Gb/s per channel over balanced copper media. The transceiver consists of two identical 10-Gb/s modules. Each module operates off a single 1.2-V supply and has a single 5-GHz phase-locked loop to supply a reference clock to two transmitter (Tx) channels and two receiver (Rx) channels. To track the input-signal phase, the Rx channel has a clock recovery unit (CRU), which uses a phase-interpolator-based timing generator and digital loop filter. The CRU can adjust the recovered clock phase with a resolution of 1.56 ps. Two sets of two-channel transceiver units were fabricated in 0.11-/spl mu/m CMOS on a single test chip. The transceiver unit size was 1.6 mm /spl times/ 2.6 mm. The Rx sensitivity was 120-mVp-p differential with a 70-ps phase margin for a common-mode voltage ranging from 0.6 to 1.0 V. The evaluated jitter tolerance curve met the OC-192 specification.

A 10-Gb/s receiver with series equalizer and on-chip ISI monitor in 0.11-/spl mu/m CMOS

A 10-Gb/s receiver is presented that consists of an equalizer, an intersymbol interference (ISI) monitor, and a clock and data recovery (CDR) unit. The equalizer uses the Cherry-Hooper topology to achieve high-bandwidth with small area and low power consumption, without using on-chip inductors. The ISI monitor measures the channel response including the wire and the equalizer on the fly by calculating the correlation between the error in the input signal and the past decision data. A switched capacitor correlator enables a compact and low power implementation of the ISI monitor. The receiver test chip was fabricated by using a standard 0.11-/spl mu/m CMOS technology. The receiver active area is 0.8 mm/sup 2/ and it consumes 133 mW with a 1.2-V power supply. The equalizer compensates for high-frequency losses ranging from 0 dB to 20 dB with a bit error rate of less than 10/sup -12/. The areas and power consumptions are 47 /spl mu/m /spl times/ 85 /spl mu/m and 13.2 mW for the equalizer, and 145 /spl mu/m /spl times/ 80 /spl mu/m and 10 mW for the ISI monitor.

A 40-Gb/s CMOS clocked comparator with bandwidth modulation technique

A differential comparator that can sample 40-Gb/s signals and that operates off a single 1.2-V supply was designed and fabricated in 0.11-/spl mu/m standard CMOS technology. It consists of a front-end sampler, a regenerative stage, and a clocked amplifier to provide a small aperture time and a high toggle rate. The clocked amplifier employs a bandwidth modulation technique that switches the feedback gain to reduce the reset time while keeping the effective gain high. We confirmed that the comparator receives a 40-Gb/s data stream at a toggle rate of 10 GHz with bit error rate less than 10/sup -12/ by laboratory measurements.

A Single-40 Gb/s Dual-20 Gb/s Serializer IC With SFI-5.2 Interface in 65 nm CMOS

This paper presents a 40 Gb/s serializer IC in 65 nm bulk CMOS technology. The IC has an SFI5.2-compliant 10 Gb/s input interface and supports two different output modes, single 40 Gb/s for OC-768 VSR and dual 20 Gb/s for DQPSK. The IC is evaluated on a PCB and error-free operation is confirmed. The chip consumes 1.8 W for the 40 G mode, and 1.6 W for the 20 G mode from 1.2 V and 3.3 V power supplies.

A 1-to-6Gb/s phase-interpolator-based burst-mode CDR in 65nm CMOS

Burst-mode clock and data recovery circuits (BMCDR) are widely used in passive optical networks (PON) [1] and as a replacement for conventional CDRs in clock-forwarding links to reduce power [2]. In PON, a single CDR performs the task of clock and data recovery for several burst sequences, each originating from a different source. As a result, the BMCDR is required to lock to an incoming data stream within tens of UIs (for example 40ns in GPON). Previous works use either injection locking [3, 4] or gated VCO [5, 6] to achieve this fast locking. In both cases, the control voltage of the CDRs VCO is generated by a reference PLL with a matching VCO to guarantee accurate frequency locking. However, any component mismatch between the two VCOs results in a frequency offset between the reference PLL frequency and the CDRs VCO frequency, and hence in a reduction of the CDRs tolerance for consecutive identical digits (CID). For example, [7] reports a frequency offset of over 20MHz (2000ppm) for 10Gb/s operation. We present a BMCDR that is based on phase interpolation (PI), eliminating the possibility of local frequency offset between the reference and recovered clock. We demonstrate 1 to 6Gb/s operation in 65nm CMOS with a locking time of less than 1UI.

A 5-Gb/s ADC-Based Feed-Forward CDR in 65 nm CMOS

This paper presents an ADC-based CDR that blindly samples the received signal at twice the data rate and uses these samples to directly estimate the locations of zero crossings for the purpose of clock and data recovery. We successfully confirmed the operation of the proposed CDR architecture at 5 Gb/s. The receiver is implemented in 65 nm CMOS, occupies 0.51 mm2, and consumes 178.4 mW at 5 Gb/s.

5 Gb/s bidirectional balanced-line link compliant with plesiochronous clocking

A 6 ns-latency 12 mW 5 Gb/s bidirectional link for short-haul (<5 m) balanced lines uses an on-chip switched-capacitor hybrid with echo-canceling capability. The clock-recovery circuit, based on a phase interpolator, makes the link tolerant to a 100 ppm difference between the frequencies of the transmit and receive clocks.

A CMOS multi-channel 10Gb/s transceiver

A quad 10Gb/s transceiver in 0.11/spl mu/m CMOS communicates electric signals over balanced copper media. The transceiver uses a single 1.2V power supply and dissipates 415mW per channel. One PLL supplies a reference clock to two transmitter channels and two receiver channels. The transceiver contains analog front ends, clock recovery units, and 312MHz parallel interfaces.

A 5Gb/s transceiver with an ADC-based feedforward CDR and CMA adaptive equalizer in 65nm CMOS

A high bandwidth and a robust performance are demanded in the consumer market applications. An ADC-based transceiver satisfies these demands and enables power/area scaling with process [1,2]. We developed and tested a spread-spectrum-clocking (SSC) compliant 5-Gb/s transceiver in 65-nm CMOS. The receiver uses an ADC-based front-end that samples the incoming signal without adjusting the phase relation between the sampling clock and the signal, hence eliminating the need for phase control of the sampling clock (Fig. 8.7.1). The phase tracking of the incoming signal and the data decision are performed entirely in the numerical domain without generating physical sampling-clock phases. An adaptive digital FFE (feed-forward equalizer) compensates for a channel loss up to 15dB at 2.5 GHz, using an on-chip adaptation controller based on CMA (constant-modulus algorithm). The CDR operated with BER less than 1E-12 when the transmitter and receiver clock signals were independently SSC-modulated at a modulation frequency of 30 kHz with a frequency deviation of 0 to −5000ppm.