This paper describes an ultra-low power SAR ADC for medical implant devices. To achieve the nano-watt range power consumption, an ultra-low power design strategy has been utilized, imposing maximum simplicity on the ADC architecture, low transistor count and matched capacitive DAC with a switching scheme which results in full-range sampling without switch bootstrapping and extra reset voltage. Furthermore, a dual-supply voltage scheme allows the SAR logic to operate at 0.4 V, reducing the overall power consumption of the ADC by 15% without any loss in performance. The ADC was fabricated in 0.13-µm CMOS. In dual-supply mode (1.0 V for analog and 0.4 V for digital), the ADC consumes 53 nW at a sampling rate of 1 kS/s and achieves the ENOB of 9.1 bits. The leakage power constitutes 25% of the 53-nW total power. Index Terms -ADC, analog-to-digital conversion, low-power electronics, successive approximation, leakage power consumption, medical implant devices. (24)

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Abstract-This paper presents an 8-GS/s, 12-bit input ∆Σ DAC with 200-MHz bandwidth in 65-nm CMOS. The high sampling rate is achieved by a two-channel interleaved MASH 1-1 digital ∆Σ modulator with 3-bit output, resulting in a highly digital DAC with only seven current cells. The two-channel interleaving allows the use of a single clock for both the logic and the final multiplexing. This requires each channel to operate at half the sampling rate, which is enabled by a high-speed pipelined MASH structure with robust static logic. Measurement results show that the DAC achieves 200-MHz bandwidth, 26-dB SNDR and -57-dBc IMD3, with a power consumption of 68-mW at 1-V digital and 1.2-V analog supplies. This architecture shows potential for use in transmitter baseband for wideband wireless communication.

This work presents an 11 GS/s 1.1 GHz bandwidth interleaved ∆Σ DAC in 65 nm CMOS for the 60-GHz radio baseband. The high sample rate is achieved by using a two-channel interleaved MASH 1-1 architecture with a 4-bit output resulting in a predominantly digital DAC with only fifteen analog current cells. Two-channel interleaving allows the use of a single clock for the logic and the multiplexing which requires each channel to operate at half sampling rate of 5.5 GHz. To enable this, a look-ahead technique is proposed that decouples the two channels within the integrator feedback path thereby improving the speed as compared to conventional loop-unrolling. Measurement results show that the ∆Σ DAC achieves a 53 dB SFDR, −49 dBc IM3 and 39 dB SNDR within a 1.1 GHz bandwidth while consuming 117 mW from 1 V digital/1.2 V analog supplies. Furthermore, the proposed ∆Σ DAC can satisfy the spectral mask of the IEEE 802.11ad WiGig standard with a second order reconstruction filter.

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