RMS-to-DC Converters

Function: Converts an AC input signal's true RMS value to a proportional DC output.

Key Features:

• True RMS measurement (accurate for complex waveforms)
• Wide bandwidth (up to MHz range in precision ICs)
• High accuracy and dynamic range
• Low power consumption (in modern ICs)

Common ICs:

• AD637 (Analog Devices) – High accuracy, up to 8 MHz
• INA333 + LOG Amp (TI) – for low-power applications
• LTC1966/LTC1967 (Analog Devices) – Delta-sigma RMS converter, 1MHz+ bandwidth

Applications:

• AC power measurement
• Audio level detection
• Signal strength measurement (RF/IF)
• Industrial sensing and control

Design Tips:

• Use low-leakage capacitors for averaging capacitor (C_AVG)
• Shield input traces for high-precision measurements
• Provide stable, low-noise supply rails
• Follow manufacturer layout guidelines for best accuracy