AD536A

Data Sheet FEATURES True rms-to-dc conversion Laser trimmed to high accuracy ±0.2% maximum error (AD536AK) ±0.5% maximum error (AD536AJ) Wide response capability Computes rms of ac and dc signals 450 kHz bandwidth: V rms > 100 mV 2 MHz bandwidth: V rms > 1 V Signal crest factor of 7 for 1% error dB output with 60 dB range Low power: 1.2 mA quiescent current Single- or dual-supply operation Monolithic integrated circuit −55°C to +125°C operation (AD536AS) GENERAL DESCRIPTION The AD536A is a complete monolithic integrated circuit that performs true rms-to-dc conversion. It offers performance comparable or superior to that of hybrid or modular units costing much more. The AD536A directly computes the true rms value of any complex input waveform containing ac and dc components. A crest factor compensation scheme allows measurements with 1% error at crest factors up to 7. The wide bandwidth of the device extends the measurement capability to 300 kHz with less than 3 dB errors for signal levels greater than 100 mV. An important feature of the AD536A, not previously available in rms converters, is an auxiliary dB output pin. The logarithm of the rms output signal is brought out to a separate pin to allow the dB conversion, with a useful dynamic range of 60 dB. Using an externally supplied reference current, the 0 dB level can be conveniently set to correspond to any input level from 0.1 V to 2 V rms. The AD536A is laser trimmed to minimize input and output offset voltage, to optimiz...