GENERAL DESCRIPTION

The AD737 is a low power, precision, monolithic, true rms-to dc converter. It is laser trimmed to provide a maximum error of ±0.2 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 physical size of this converter make it suitable for upgrading the performance of non-rms precision rectifiers in many applications. Compared to these circuits, the AD737 offers higher accuracy at equal or lower cost.

FEATURES

Computes

True rms value

Average rectified value

Absolute value

Provides

200 mV full-scale input range (larger inputs with input scaling)

Direct interfacing with 3½ digit CMOS ADCs

High input impedance: 1012 Ω

Low input bias current: 25 pA maximum

High accuracy: ±0.2 mV ± 0.3 of reading

RMS conversion with signal crest factors up to 5

Wide power supply range: ±2.5 V to ±16.5 V

Low power: 25 µA (typical) standby current

No external trims needed for specified accuracy

The AD737 output is negative-going; the AD736 is a positive output-going version of the same basic device