The AD736 is a low power, high precision, monolithic true MRS-ToDC converter. It is laser trimmed and provides ± 0.3mV ±0.3% sinusoidal input readings for maximum error. In addition, it maintains high accuracy while measuring a wide range of input waveforms, including variable duty ratio pulses and thyristor (phase) controlled sine waves. The converter has the advantages of low cost and small size, and is suitable for the performance upgrade of non-root mean square precision rectifiers.
Schematic diagram
Compared to these circuits, the AD736 provides greater accuracy at the same or lower cost and can also calculate the RMS of AC and DC input voltages. It can also be used as an AC coupling device by adding an external capacitor. In this mode, it can resolve input signal levels of 100 μV rms or lower, regardless of temperature or power supply voltage changes. For input waveforms with peak coefficients of 1 to 3, high accuracy can also be maintained.
In addition, a crest factor of up to 5 can be measured at the 200 mV full scale input level (only 2.5% additional error is introduced). The AD736 has its own output buffer amplifier, thus offering great design flexibility. It requires only 200μA of supply current and is optimized for portable multimeters and other battery-powered applications.
Working principle diagram
The AD736 allows the choice of two signal input terminals: a high-impedance FET input (1012 Ω), which interfaces directly with a high-Z input attenuator, and a low-impedance input (8 kΩ), which allows the measurement of 300 mV input levels while operating from a minimum supply voltage of + 2.8V, − 3.2V. The two inputs can be used singly or separately.
The AD736 has a 1% read error bandwidth, over 10 kHz at input amplitudes ranging from 20 mV rms to 200 mV rms, while power consumption is only 1 mW, and is available in four performance classes. The AD736J and AD736K grades are rated for commercial temperature ranges of 0°C to +70°C and −20°C to +85°C. Grades AD736A and AD736B are rated for industrial temperatures ranging from −40°C to +85°C. The AD736 is available in three low-cost 8-pin packages :PDIP, SOIC, and CERDIP.
