AD736 Datasheet | Analog Devices

FEATURES Converts an ac voltage waveform to a dc voltage and then converts to the true rms, average rectified, or absolute value 200 m V rms full-scale input range (larger inputs with input attenuator) High input impedance: 1012 Ω Low input bias current: 25 p A maximum High accuracy: ±0.3 m V ± 0.3% of reading RMS conversion with signal crest factors up to 5 Wide power supply range: +2.8 V, - 3.2 V to ±16.5 V Low power: 200 µA maximum supply current Buffered voltage output No external trims needed for specified accuracy Related device: the AD737- features a power-down control with standby current of only 25 μA; the dc output voltage is negative and the output impedance is 8 kΩ GENERAL DESCRIPTION The AD736 is a low power, precision, monolithic true rms-todc converter. It is laser trimmed to provide a maximum error of ±0.3 m V ± 0.3% of reading with sine wave inputs. Furthermore, it maintains high accuracy while measuring a wide range of input waveforms, including variable duty-cycle pulses and triac (phase)-controlled sine waves. The low cost and small size of this converter make it suitable for upgrading the performance of non-rms precision rectifiers in many applications. pared to these circuits, the AD736 offers higher accuracy at an equal or lower cost. The AD736 can pute the rms value of both ac and dc input voltages. It can also be operated as an ac-coupled device by adding one external capacitor. In this mode, the AD736 can resolve input signal levels of 100 μV rms or less, despite variations in temperature or supply voltage. High accuracy is also maintained for input waveforms with crest factors of 1 to 3. In addition, crest factors as high as 5 can be measured (introducing only 2.5% additional error) at the 200 m V full-scale input level. The AD736 has its own output buffer amplifier, thereby providing a great deal of design flexibility. Requiring only 200 µA of power supply current, the AD736 is optimized for use in portable multimeters and other battery-powered...