Hybrid ADCs, Smart Sensors for the IoT, and Sub-1V & Advanced Node Analog Circuit Design by Pieter Harpe Kofi A. A. Makinwa & Andrea Baschirotto

Author:Pieter Harpe, Kofi A. A. Makinwa & Andrea Baschirotto
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

9.5 Measurement Results

Figure 9.11 shows measurement data of the LDO output voltage and PTAT current over the complete supply range from 1.5 to 5.5 V obtained over ∼50 samples. A DC PSSR of 38 dB can be extracted. The PTAT current varies by ±7.5% over the supply range corresponding to a conductance of 0.37 nS. Regarding the spread, σ/μ reaches 2.8% and 0.8% for the PTAT current and LDO output voltage, respectively.

Fig. 9.11PTAT current and LDO voltage spread at several supply voltages

Figure 9.12 shows XO calibration data obtained over ∼1000 samples during the calibration procedure. Temperature gradients among parts in the oven are not compensated affecting the reported figures pessimistically. Over −40 to 85 °C, the XO’s temperature stability varies by some 200 ppm. After individual trimming by laser, the frequency at ambient temperature lies well within the ±20 ppm claimed previously. The ToT (or similarly the first-order TCF) of the XO is reduced to a mean value of 18 °C—compared to 23 °C for the XTAL—most likely due to the effect of the temperature dependency of the XO circuit capacitance. The ToT variance is 2 °C mostly affected by variations in the tines etching. The parabolic coefficient reaches −37 ppb/°C2, with a standard deviation over mean value of 3.8%.

Fig. 9.12Measured XO statistics on ∼1000 samples

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