GENERAL DESCRIPTION

The AD8436 is a new generation, translinear precision, low power, true rms-to-dc converter loaded with options. It computes a precise dc equivalent of the rms value of ac waveforms, including complex patterns such as those generated by switch mode power supplies and triacs. Its accuracy spans a wide range of input levels (see Figure 2) and temperatures. The ensured accuracy of ≤±0.5 and ≤10 μV output offset result from the latest Analog Devices, Inc., technology. The crest factor error is <0.5 for CF values between 1 and 10.

The AD8436 delivers true rms results at less cost than misleading peak, averaging, or digital solutions. There is no programming expense or processor overhead to consider, and the 4 mm  4 mm package easily fits into tight applications. On-board buffer amplifiers enable the widest range of options for any rms-to-dc converter available, regardless of cost. For minimal applications, only a single external averaging capacitor is required. The built-in high impedance FET buffer provides an interface for external attenuators, frequency compensation, or driving low impedance loads. A matched pair of internal resistors enables an easily configurable gain-of-two or more, extending the usable input range even lower. The low power, precision input buffer makes the AD8436 attractive for use in portable multi-meters and other battery-powered applications.

FEATURES

Delivers true rms or average rectified value of ac waveform

Fast settling at all input levels

Accuracy: ±10 μV ± 0.25 of reading (B grade)

Wide dynamic input range

100 μV rms to 3 V rms (8.5 V p-p) full-scale input range

Larger inputs with external scaling

Wide bandwidth:

1 MHz for −3 dB (300 mV)

65 kHz for additional 1 error

Zero converter dc output offset

No residual switching products

Specified at 300 mV rms input

Accurate conversion with crest factors up to 10

Low power: 300 µA typical at ±2.4 V

High-Z FET separately powered input buffer

RIN ≥ 1012 Ω, CIN ≤ 2 pF

Precision dc output buffer

Wide power supply voltage range

Dual: ±2.4 V to ±18 V; single: 4.8 V to 36 V

4 mm × 4 mm LFCSP and 8 mm × 6 mm QSOP packages

ESD protected