A 16b Clockless Digital-to-Analog Converter with Ultra-Low-Cost Poly Resistors Supporting Wide-Temperature Range from -40°C to 85°C

High-precision digital-to-analog converter (DAC) is a critical component in process control, data acquisition, and testing instruments. In order to achieve high resolution and a wide-temperature range, conventional designs have been adopting high-cost thin-film resistors with laser-trimming to improve the matching property and thus the DAC resolution. In this work, targeting at lowering the cost, we propose an analog resistor redundancy, full code, and piecewise-linear calibration scheme to enable the use of low-cost poly resistors in a standard CMOS process. In order to overcome the drift over a wide temperature range, a feedback circuit is proposed to guarantee that the resistance of the switch can track the resistor with temperature changes. Therefore, the DAC can be calibrated under a specific temperature and tested under an arbitrary temperature from -40℃ to 85℃ using the same calibration codes. The 16b DAC was implemented in a 0.25μm 5V CMOS process with 5V CMOS devices and poly resistors rather than thin film resistor. The test result shows that it can achieve the INL≤0.5LSB, INL≤4LSB, and INL≤4LSB at 25&8451;C, -40℃C, and 85℃C, respectively, using the same calibration code. It settles in 1μs and it has below 5nV ⋅ s glitch. The current consumption is 1.7mA from 5V voltage supplies.