LTC1966HMS8-PBF View Datasheet(PDF) - Linear Technology

Part Name

Description

Manufacturer

LTC1966HMS8-PBF

Precision Micropower ∆∑ RMS-to-DC Converter

Linear Technology 

LTC1966

Applications Information

The calculations of the error terms for a 200mV full-scale

case are:

Gain = Reading at 200mV – Reading at 20mV

180mV

Output Offset = Reading at 20mV – 20mV

Gain

DC, 2 Point

DC based calibration is preferable in many cases because a

DC voltage of known, good accuracy is easier to generate

than such an AC calibration voltage. The only down side

is that the LTC1966 input offset voltage plays a role. It is

therefore suggested that a DC based calibration scheme

check at least two points: ±full-scale. Applying the –full-

scale input can be done by physically inverting the voltage

or by applying the same +full-scale input to the opposite

LTC1966 input.

For an otherwise AC-coupled application, only the gain

term may be worth correcting for, but for DC-coupled ap-

plications, the input offset voltage can also be calculated

and corrected for.

The calculations of the error terms for a 200mV full-scale

case are:

Gain = Reading at 200mV + Reading at – 200mV

400mV

Input Offset = Reading at – 200mV – Reading at 200mV

2 •Gain

Note: Calculation of and correction for input offset voltage

are the only way in which the two LTC1966 inputs (IN1,

IN2) are distinguishable from each other. The calculation

above assumes the standard definition of offset; that a

positive offset is the case of a positive voltage error inside

the device that must be corrected by applying a like nega-

tive voltage outside. The offset is referred to whichever

pin is driven positive for the +full-scale reading.

DC, 3 Point

One more point is needed with a DC calibration scheme

to determine output offset voltage: +10% of full scale.

The calculation of the input offset is the same as for the

2‑point calibration above, while the gain and output offset

are calculated for a 200mV full-scale case as:

Gain = Reading at 200mV – Reading at 20mV

180mV

Output Offset =

Reading at 200mV +Reading at – 200mV – 400mV • Gain

2

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