یک سوئیچ آنالوگ جدید برای مدارهای خازن سوئیچ‌شده دقت بالا

نوع مقاله : علمی-پژوهشی

نویسندگان

دانشکده مهندسی برق - دانشگاه علم و صنعت ایران

چکیده

عملکرد مدارهای خازن سوئیچ‌شده به میزان قابل توجهی به سوئیچ‌های آنالوگ مورد استفاده در آن‌ها وابسته است. خطاهای تزریق بار کانال، نفوذ کلاک و نشتی حالت خاموش اصلی‌ترین عوامل محدود‌کننده دقت این سوئیچ‌های آنالوگ هستند. در این مقاله روشی نوین برای کمینه‌کردن این خطاها با استفاده از ساختاری بسیار ساده معرفی شده است. برای ارزیابی عملکرد سوئیچ پیشنهادی، شبیه‌سازی‌ها با استفاده از فن‌آوری 0.18 μm انجام شده است. نتایج شبیه‌سازی‌ها نشان می‌دهند مقاومت روشن سوئیچ پیشنهادی در سراسر محدوده سیگنال ورودی کم‌تر از Ω560 می‌باشد که این میزان مقاومت مشخصات موردنیاز پهنای‌باند دنباله‌روی سوئیچ را به‌طور کامل برآورده می‌سازد. به‌علاوه، از آنجایی‌که مقاومت خاموش سوئیچ پیشنهادی بسیار زیاد (چند گیگااهم) است، جریان نشتی آن بسیار ناچیز می‌باشد. هم‌چنین شبیه‌سازی‌ها نشان می‌دهند که خطاهای ناشی از سوئیچ با استفاده از روش پیشنهادی به‌طور قابل ملاحظه‌ای کاهش یافته است. میزان بار خطای ایجاد شده در خروجی ناشی از تزریق بار و نفوذ کلاک در محدوده وسیعی از تغییرات ورودی کم‌تر از fC 1.6 می‌باشد. هم‌چنین سوئیچ پیشنهادی به ازای ورودی سینوسی با فرکانس MHz 2.5 و دامنه mV800 و نیز فرکانس کلاک MHz200 با ولتاژ تغذیهV 1.8 دارای SNDR برابر باdB 80.55، ENOB برابر با 13.08، THD برابر با dB -81.41 و SFDR برابر با dB 87.7 می‌باشد. 

کلیدواژه‌ها


عنوان مقاله [English]

A Novel Analog Switch for High Precision Switched-Capacitor Applications

نویسندگان [English]

  • S. Naghavi
  • A. Abrishamifar
School of Electrical Engineering, Iran University of Science and Technology , Tehran, Iran
چکیده [English]

The performance of a switched capacitor circuit strongly depends on its analog switches. This paper introduces a new technique to design a high precision analog MOS switch for switched-capacitor applications. To satisfy the accuracy requirements of the switch, a novel technique is proposed to minimize the charge injection and clock feed-through errors by using a very simple structure. Moreover, an innovative approach to increase the off-resistance of the switch and consequently minimizing its leakage current is presented. In order to evaluate the performance of the proposed switch, simulations are done in a 18μm standard CMOS technology. The on-resistance of the proposed switch is less than 560Ω over entire input signal range which completely satisfies the tracking bandwidth requirements. In addition, since the proposed switch provides an ultra-high off-resistance in the range of several GΩs, the leakage current of the proposed switch is negligible. Simulation results also show that switch induced errors are significantly eliminated by using the proposed cancellation technique. The output error charge due to charge injection and clock feed-through over a wide range of the input signal variation is less than 1.6fC. Moreover, simulation results show that the proposed switch achieves signal to noise plus distortion ratio (SNDR) of 80.55dB, effective number of bits (ENOB) of 13.08, total harmonic distortion (THD) of -81.41dB and spurious-free dynamic range (SFDR) of 87.7dB for a 2.5MHz sinusoidal input of 800mv peak-to-peak amplitude at 200MHz sampling rate with a 1.8V supply voltage.

کلیدواژه‌ها [English]

  • Analog switch
  • channel charge injection
  • clock feed-through
  • sub-threshold leakage
  • switched capacitor circuit
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