AD737It is a low-power, precision, single-chip true rmsDC converters。 It is laser trimmed and has a maximum error of ±0.2 mV ± 0.3% of reading with a sine wave input. In addition, it measures a wide range of input waveforms with high accuracy, including variable duty cycle pulses and triac (phase)-controlled sine waves. The converter's low cost and small size make it suitable for upgrading non-rms precision rectifier performance in many applications. Compared to these circuits, the AD737 provides higher accuracy at the same or lower cost.
The AD737 can calculate RMS values for ac and dc input voltages. With the addition of an external capacitor, it can also operate in AC-coupled mode. In this mode, the AD737 can resolve input signal levels of 100 μV rms or lower, even in the presence of temperature or supply voltage fluctuations. High accuracy is also maintained for input waveforms with crest factors of 1 to 3. In addition, at a 200 mV full-scale input level, the crest factor can be as high as 5 (the measurement introduces only an additional error of 2.5%).
AD737There is no output buffer amplifier, which greatly reduces the dc offset error at the output, which makes it highly compatible with high input impedance ADCs.
It offers a supply current of only 160 μA and is optimized for portable multimeters and other battery-powered applications. In power-down mode, the standby supply current is typically 25 μA.
The AD737 provides both high impedance (1012 Ω) and low impedance inputs. The high-impedance FET input can be connected directly to a high-source impedance input attenuator, and the low-impedance (8 kΩ) input can operate at a minimum supply voltage of ±2.5 V while accepting a rms voltage of 0.9 V. Both inputs can be single-ended or differential.
The AD737 achieves a 1% reading error bandwidth, exceeding 10 kHz for input amplitudes from 20 mV rms to 200 mV rms, and consuming only 0.72 mW.
The AD737 is available in two grades based on performance. The AD737J and AD737K operate over the 0°C to 70°C commercial temperature range. The AD737JR-5 was tested at a dc supply voltage of ± 2.5 V. The AD737A operates over the industrial temperature range of −40°C to +85°C. The AD737 is available in two low cost 8-lead packages: PDIP and SOIC_N.
Product features
1. Regardless of its waveform, the average rectified, absolute, or true rms value of a signal can be calculated.
2. The AD737 requires only one external component to perform true rms measurements: an averaging capacitor.
3. The standby power consumption of the AD737 is only 125 μW, making it suitable for battery-powered applications.