GENERAL DESCRIPTION

The AD736 is a low power, precision, monolithic true rms-to dc converter. It is laser trimmed to provide a maximum error of ±0.3 mV ± 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. Compared to these circuits, the AD736 offers higher accuracy at an equal or lower cost.

FEATURES

Converts an ac voltage waveform to a dc voltage and then

converts to the true rms, average rectified, or absolute value

200 mV rms full-scale input range (larger inputs with input

attenuator)

High input impedance: 1012 ?

Low input bias current: 25 pA maximum

High accuracy: ±0.3 mV ± 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 k?