AD737 IC – RMS to DC Converter IC

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 the AD737 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. The AD737 computes the rms value of both ac and dc input voltages, and is ac-coupled by adding an input capacitor. In this mode, the AD737 resolves input signal levels of 100 μV rms or less, despite variations in temperature or supply voltage. High accuracy is maintained for input waveforms with crest factors of 1 to 3 and crest factors at 2.5% or less with respect to full-scale input level. The AD737 has no output buffer amplifier, thereby significantly reducing dc offset errors occurring at the output and making the device highly compatible with high input impedance ADCs. Requiring only 160 μA of power supply current, the AD737 is optimized for use in portable multimeters and other battery powered applications. In power-down mode, the standby supply current in is typically 25 μA. The AD737 has both high (1012 Ω) and low impedance input options. The high-Z FET input connects high source impedance input attenuators, and a low impedance (8 kΩ) input accepts rms voltages of up to 0.9 V while operating from the minimum power supply voltage of ±2.5 V. The two inputs can be used either single-ended or differentially. The AD737 achieves 1% of reading error bandwidth, exceeding 10 kHz for input amplitudes from 20 mV rms to 200 mV rms, while consuming only 0.72 mW. The AD737 is available in two performance grades. The AD737J and AD737K grades operate over the commercial temperature range of 0°C to 70°C. The AD737JR-5 is tested with supply voltages of ±2.5 V dc. The AD737A grade operates over the industrial temperature range of −40°C to +85°C. The AD737 is available in two low cost, 8­lead packages: PDIP and SOIC_N.

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 analog-to-digital converters (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

Specification:-

Related Document:-

 AD737 IC Data Sheet