2018 Volume 15 Issue 11 Pages 20180377
For medical implantable devices, power consumption is the most important design consideration. This is because only medium data rate and medium resolution are required in such applications. In addition, rail-to-rail output swing is desired if power supply voltage is near 1 V. In order to achieve low power consumption with medium data rate and resolution, this paper proposes a low-power resistor-string and current-steering hybrid digital-to-analog converter (R-I DAC) with a full-swing output signal. It adopts a current-direction control which makes the output current of the current-steering block flow bi-directionally through the feedback resistor. The proposed structure can achieve full-swing output. It consumes half of the total current of the conventional single-ended current-steering DAC for the same output swing. A 10-bit full-swing R-I DAC prototype is implemented by 180-nm CMOS technology. The measured effective number of bits (ENOB) is 8.9 bits. The settling time of pulse response is 300 ns which corresponds to 3.3 MHz sampling frequency. Chip area is 0.22 mm2. For 1.25 V single power supply, the output swing is 1.024 V. The power consumption is 0.41 mW for a full-swing sinusoidal input of 40.82 kHz at a 3.125 MS/s sampling clock.