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ADI公司的AD8436是新一代跨導線性的高精度低功耗真正的RMS/DC轉換器，它能精確計算交流波形的rms值，包括由開關電源和TRIAC所產品的復數項。精度優于0.5%，輸出失調小于10uV，波峰因素（CF=1-10）時的誤差小于0.5%,輸入范圍滿刻度為100 μV rms 到3 V rms (8.5 V p-p)，雙電源電壓為 ±2.4 V到±18 V ，單電源電壓為4.8 V 到36 V，主要用在遙控，手持儀表，板空間受限和戶外環境的電源和汽車。本文介紹了AD8436主要特性，功能方框圖，RMS核方框圖，波峰因素測試電路圖，典型應用電路以及AD8436-EVALZ評估板電路圖和PCB布局圖。 The AD8436 is a new generation, translinear precision, low power, true rms-to-dc converter that is loaded with options. It computes a precise dc equivalent of the rms value of ac waveforms, including complex patterns such as those generated by switchmode power supplies and triacs. Its accuracy spans a wide range of input levels and temperatures. The ensured accuracy of ≤±0.5% and ≤10 μV output offset result from the latest Analog Devices, Inc., technology. The crest factor error is <0.5% for CF values between 1 and 10. The AD8436 delivers instant true rms results at less cost than misleading peak, averaging, or digital solutions. There is no programming expense or processor overhead to consider, and the 4 mm × 4 mm package easily fits into those tight applications. On-board buffer amplifiers enable the widest range of options for any rms-to-dc converter available, regardless of cost. For minimal applications, only a single external averaging capacitor is required. The built-in high impedance FET buffer provides an interface for external attenuators, frequency compensation, or driving low impedance loads. A matched pair of internal resistors enables an easily configurable gain-of-two or more, extending the usable input range even lower. The low power, precision input buffer makes the AD8436 attractive for use in portable multi- meters and other battery-powered applications. The precision dc output buffer offers extremely low offset voltages, thanks to bias current cancellation. Unlike digital solutions, the AD8436 has no switching circuitry limiting performance at high or low amplitudes (see Figure 2). A usable response of <100 μV and >3 V extends the dynamic range with no external scaling, accommodating the most demanding low signal conditions. The AD8436 operates from single or dual supplies of ±2.4 V (4.8 V) to ±18 V (36 V). A and J grades are available in a compact 4 mm × 4 mm, 20-lead chip-scale package. The operating temperature ranges are −40°C to 125°C and 0°C to 70°C. The AD8436 is a good choice for remote, portable battery-powered instrumentation, energy and automotive applications where limited board space and outdoor environments are considerations. AD8436主要特性： Computes true rms value instantly Accuracy: ±10 μV ± 0.5% of reading Wide dynamic input range 100 μV rms to 3 V rms (8.5 V p-p) full-scale input range Larger inputs with external scaling Wide bandwidth: 1 MHz for −3 dB (300 mV) 65 kHz for additional 1% error Zero converter dc output offset No residual switching products Specified at 300 mV rms input Accurate conversion with crest factors up to 10 Low power: 300 μA typical at ±2.4 V Fast settling at all input levels High-Z FET separately powered input buffer RIN ≥ 1012 Ω, CIN ≤ 2 pF Precision dc output buffer Wide supply range Dual: ±2.4 V to ±18 V Single: 4.8 V to 36 V Small size: 4 mm × 4 mm package ESD protected 
圖1。AD8436功能方框圖
圖2。AD8436 RMS核方框圖
圖3。波峰因素測試電路圖
圖4。AD8436典型應用電路 AD8436-EVALZ評估板 The AD8436-EVALZ provides a platform to evaluate AD8436 performance. The board is fully assembled, tested and ready to use after the power and signal sources are connected. Figure 45 is a photograph of the board. Signal connections are located on the primary and secondary sides, with power and ground on the inner layers. The AD8436-EVALZ offers many options, without sacrificing simplicity. The board is tested and shipped with a 10 μF averaging capacitor (CAVG), 3.3 μF low-pass filter capacitor (C8) and a 0.1 μF (COPT) capacitor to optimize crest factor performance. To evaluate minimum cost applications, remove C8 and COPT.
圖5。AD8436-EVALZ評估板外形圖
圖6。AD8436-EVALZ評估板電路圖
圖7。AD8436-EVALZ評估板元件布局圖 詳情請見： http://www.analog.com/static/imported-files/data_sheets/AD8436.pdf |
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ADI推出一款集成式真RMS-to-DC:AD8436 Analog Devices, Inc.(ADI)，最近推出一款集成式真 RMS-to-DC AD8436，它提供一流的100 µV至3 V可用動態范圍，能夠以高精度測量極低的信號電平，且建立時間內無壓降。 AD8436是一款精密單芯片RMS-to-DC轉換器(http://www.analog.com/zh/pr0816/ad8436)，其交流轉換精度優于±0.5%，各種不同輸入值的建立時間相同，使得轉換速率恒定不變，同時可即刻顯示交流輸入幾乎為零以及高電平交流輸入時的轉換結果。AD8436不受溫度、波峰因數和電源電壓變化的影響。轉換器輸出的零直流失調電壓可簡化校準程序。它集成FET輸入和精密直流緩沖放大器，功耗僅300 uA，采用緊湊型4 mm x 4 mm封裝。AD8436 特別適合需要考慮有限的電路板空間和室外應用環境的遠程便攜電池供電儀器、能源和汽車應用。 RMS（均方根）是交流和直流信號幅度的基本量度，與簡單的均值方法相比，這是一種更好的信號功率測量方法。RMS-to-DC 轉換器適合必須實現交流/直流信號低功耗精密測量的應用場合。借助 AD8436 的片上系統設計，可算出 RMS 的精確直流等效值，并在整個輸入范圍內提供一定水平的線性度和精度，有助于工程師設計出90 dB動態范圍的系統。 AD8436 將波峰因數擴展到10（約為目前業界標準數字解決方案的兩倍），最大程度地保證精度。它特別適用于高躍遷信號，可用于目前使用 ADI 公司的AD736和AD737等低功耗、真 RMS-to–DC 轉換器的設計，使性能有所提升。該器件經激光調整，具有300mV的 RMS 輸入，采用雙電源和單電源供電。AD8436 是第一款能夠在-40°C至125°C的擴展工業溫度范圍內工作的RMS-to-DC轉換器，同時還提供0°C至70°C溫度范圍的版本。 AD8436精密、低功耗、單芯片真均方根直流轉換器的主要特性： 即時計算真有效值 任意輸入電平下的建立時間均快速、恒定 寬可用動態范圍：100 uV RMS至3 VRMS (8.5 V p-p) 滿量程 輸入頻率范圍：65 kHz，額外誤差1% 低功耗：±2.4 V時典型值為300 µA 精度：±10 μV ，最大讀數的0.5% 片上系統包括帶精密增益設置電阻的FET輸入緩沖和輸出緩沖 電源電壓范圍： 雙電源：+/-2.4 V至+/-18 V 單電源：4.8 V至36 V AD8436的配套產品包括24位Σ-Δ型ADC AD7190和微功耗、高精度基準電壓源ADR3433，適合低噪聲、低功耗精密應用。 |
