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LTC1966CMS8#TRPBF

Precision delta-sigma RMS-to-DC converter, 0.1% accuracy, 800kHz BW, 155uA Iq, MSOP-8

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Manufacturer Part：

LTC1966CMS8#TRPBF

Package：

MSOP-8 (3.00 x 3.00 x 0.85 mm)

Brand：

Product Categories：

Analog Linear ICs, Integrated Circuits ICs

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Description

Product Overview

The LTC1966CMS8#TRPBF from Analog Devices is a precision micropower delta-sigma RMS-to-DC converter in an 8-lead MSOP package. Using a patented delta-sigma computational technique, it achieves 0.1% gain accuracy from 50 Hz to 1 kHz and 0.02% linearity while consuming only 155 µA supply current, requiring just a single external capacitor for operation.

Key Specifications

Gain Accuracy	0.1% (50 Hz to 1 kHz)
Total Error	0.25% (50 Hz to 1 kHz)
Linearity	0.02%
Bandwidth (-3 dB)	800 kHz
Supply Current	155 µA (typ)
Shutdown Current	0.1 µA
Supply Voltage	2.7 V to 5.5 V single, or up to +/-5.5 V dual
Crest Factor Support	Up to 4
Operating Temperature	0°C to +70°C (C-grade)
Package	8-MSOP

Features

Patented delta-sigma RMS computation eliminates log-antilog errors
0.02% linearity enables simple system calibration at any input voltage
Rail-to-rail input common mode and differential input support
Separate output reference pin for flexible level shifting
Only one external averaging capacitor required
Ultralow 0.1 µA shutdown current
Insensitive to PCB soldering stresses and temperature

Applications

True RMS digital multimeters and panel meters
AC + DC true RMS measurements
Power monitoring and energy metering
Audio level detection and VU metering
Variable-speed drive current sensing

Product Introduction:LTC1966CMS8#TRPBF Product Introduction

The LTC1966CMS8#TRPBF is a precision micropower RMS-to-DC converter from Analog Devices that uses an innovative patented delta-sigma computational technique instead of conventional log-antilog methods. This approach delivers 0.1% gain accuracy from 50 Hz to 1 kHz, 0.25% total error, and 0.02% linearity, enabling simple single-point system calibration. The device accepts single-ended or differential input signals with rail-to-rail common mode range and supports crest factors up to 4. The rail-to-rail output features a separate reference pin for flexible level shifting. Operating from a 2.7 V to 5.5 V single supply or up to +/-5.5 V dual supplies, the LTC1966 draws only 155 µA typical supply current and features a 0.1 µA shutdown mode. The 800 kHz -3 dB bandwidth is constant and independent of input voltage, a significant advantage over log-antilog converters. Packaged in a space-saving 8-lead MSOP, it requires only one external averaging capacitor.

Working Principle:LTC1966CMS8#TRPBF Working Principle

The LTC1966 employs a delta-sigma modulator as the computational core for RMS-to-DC conversion, replacing traditional log-antilog circuits. The input signal is applied to a second-order delta-sigma modulator whose reference is derived from the output voltage. The modulator produces a single-bit stream whose average duty cycle equals VIN/VOUT. This bit stream controls a polarity switch that selectively buffers or inverts the input signal, effectively performing the multiplication VIN x (VIN/VOUT) = VIN^2/VOUT before a low-pass averaging filter. The steady-state output satisfies VOUT = RMS(VIN), completing the implicit RMS computation. Unlike log-antilog methods, the delta-sigma approach operates at only two gain states (+1 and -1), providing exceptional linearity of 0.02% that is independent of amplitude. The low-pass filter is implemented with a single external capacitor across the high-impedance (85 kohm) output, and its corner frequency determines the measurement bandwidth and settling time.

Pin Description:LTC1966CMS8#TRPBF Pin Definition and Functions

Pin	Name	Type	Function
1	VDD	Power	Positive supply voltage (2.7 V to 5.5 V)
2	IN1	Input	Differential input, non-inverting (VIN+)
3	IN2	Input	Differential input, inverting (VIN-)
4	VSS	Power	Negative supply (GND for single supply, -5.5 V max for dual)
5	OUTRTN	Output	Output return (reference) pin for level shifting
6	OUT	Output	RMS DC output voltage
7	CAVE	Output	Averaging capacitor connection (connect to OUT via external cap)
8	ENABLE	Input	Shutdown control; high = active, low = shutdown (0.1 µA)

Application Scenarios:In which products and applications isLTC1966CMS8#TRPBF used

Digital Multimeters: True RMS AC voltage and current measurement in handheld and bench DMMs
Power Monitoring: Real-time RMS current and voltage measurement in energy metering systems
Audio Level Detection: VU metering and audio signal RMS level measurement in professional audio equipment
Industrial Process Control: Variable-speed drive current sensing and motor load monitoring
AC + DC RMS Measurement: Combined AC and DC RMS measurement in precision instrumentation

Alternative Models:What chips are recommended as replacements for LTC1966CMS8#TRPBF

Model	Manufacturer	Accuracy	Bandwidth	Supply	Package	Notes
LTC1967IMS8#TRPBF	Analog Devices	0.1%	800 kHz	2.7-5.5 V	MSOP-8	Industrial temp range
AD736JRZ	Analog Devices	0.3%	400 kHz	2.8-16.5 V	SOIC-8	Log-antilog, wider supply
AD8436JCPZ	Analog Devices	0.1%	1 MHz	2.7-12 V	LFCSP-16	Higher bandwidth
LTC1966HMS8#TRPBF	Analog Devices	0.1%	800 kHz	2.7-5.5 V	MSOP-8	Extended temp -40 to 125C
MX536AJCWE	Maxim (ADI)	0.2%	600 kHz	4-36 V	SOIC-16	Log-antilog legacy part