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RMS-to-DC Converter Ensures Accuracy and Best-in-Class Dynamic Range

Wed, 08/17/2011 - 12:08pm

Analog Devices (ADI) unveiled today an integrated true RMS-to-DC converter that offers a best-in-class 100 µV to 3 V of usable dynamic range and the ability to measure extremely low signal levels with high accuracy and no drop in settling time. 

The AD8436 precision monolithic true RMS-to-DC converter features AC conversion accuracy to better than ± 0.5 percent. Uniform settling for widely variant input values enables consistent conversion rates with results displayed promptly for near-zero and high-level AC inputs. The AD8436 is immune to temperature, crest factor and supply voltage variations. Zero DC offset voltages at the converter output simplify calibration. This performance is packed into a compact 4 mm x 4 mm package integrated with a FET input and precision DC buffer amplifiers and consumes only 300 uA of power. The AD8436 is a good choice for remote, portable battery-powered instrumentation, energy and automotive applications where limited board space and outdoor environments are considerations.

RMS (root mean square) is a fundamental measurement of the magnitude of an AC and DC signal and is a better measure of the power in a signal than simple averaging. RMS-to-DC converters are used in applications where precise, low power measurement of AC/DC signals is the prime objective. The AD8436 system-on-a-chip design computes the precise DC equivalent of the RMS value and provides a level of linearity and accuracy across the entire input range that enables engineers to design systems with 90 dB of dynamic range.

The AD8436 extends the crest-factor to 10 – approximately double the current industry-standard digital solution – with minimal loss of accuracy. It is particularly useful for high transit signals and can be used in designs currently using ADI’s low-power, true RMS-to-DC converters such as the AD736 and AD737 with improved performances. The device is laser trimmed and characterized at 300-mV RMS input and comes with dual and single power supplies. The AD8436 is the first RMS-to-DC converter specified to operate in the extended industrial temperature range of -40°C to 125°C. It is also available in a 0°C to 70°C temperature range version.

AD8436 Precision, Low Power, Monolithic True RMS-to-DC Converter Key Features:

  • Instantly computes true RMS value
    • Fast and constant settling time at all input levels
    • Wide usable dynamic range: 100 uV RMS to 3 VRMS (8.5 V p-p) full-scale
    • Input frequency range: 65 kHz for additional 1 percent error
    • Low power: 300 µA typical at ±2.4 V
    • Accuracy: ±10 ?V ± 0.5 percent of reading max
  • System-on-a-chip includes FET input buffer with precision gain setting resistors, output buffer
  • Supply range:
    • Dual: +/-2.4 V to +/-18 V
    • Single: 4.8 V to 36 V

Availability, Pricing and Complementary Components

 

Product

 

 

 

Availability

 

 

 

Temperature
Range

 

 

 

Price Each
Per 1,000

 

 

 

Packaging

AD8436A

 

 

 

Full volume
production now

 

 

 

-40?C to 125?C

 

 

 

$4.95

 

 

 

20-lead LFCSP
4 mm x 4 mm

AD8436J

 

 

 

Full volume
production now

 

 

 

0?C to 70?C

 

 

 

$2.95

 

 

 

20-lead LFCSP
4 mm x 4 mm

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
Complementary components to the AD8436 in low noise, low power, precision applications include the AD7190 24-bit Sigma Delta A/D converter and the ADR3433 micropower, high accuracy voltage references.

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