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