LMP90100MHESLASHNOPB datasheet(28/69 Pages) TI1

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Calibration

Background

calibration

System

calibration

Correction

Estimation

Offset

Gain

Pins

D0 ± D6 =

Set

GPIO_DIRCNx = 0

Set

GPIO_DIRCNx = 1

Write to GPIO_DAT: Dx bit

to drive Dx high or low,

where 0 ” [ ” 6.

inputs

outputs

Read the

GPIO_DAT: Dx bit to

determine if Dx is

high or low, where

0 ” [ ” 6.

LMP90100

SNAS510P – JANUARY 2011 – REVISED MARCH 2013

www.ti.com

Figure 43. GPIO Register Settings

CALIBRATION

As seen in Figure 44, there are two types of calibration: background calibration and system calibration. These

calibrations are further described in the next sections.

Figure 44. Types of Calibration

Background Calibration

Background calibration is the process of continuously determining and applying the offset and gain calibration

coefficients to the output codes to minimize the LMP90xxx’s offset and gain errors. Background calibration is a

feature built into the LMP90xxx and is automatically done by the hardware without interrupting the input signal.

Four differential channels, CH0-CH3, each with its own gain and ODRs, can be calibrated to improve the

accuracy.

Types of Background Calibration:

Figure 44 also shows that there are two types of background calibration:

1. Type 1: Correction - the process of continuously determining and applying the offset and gain calibration

coefficients to the output codes to minimize the LMP90xxx’s offset and gain errors.

–

This method keeps track of changes in the LMP90xxx's gain and offset errors due to changes in the

operating condition such as voltage, temperature, or time.

2. Type 2: Estimation - the process of determining and continuously applying the last known offset and gain

calibration coefficients to the output codes to minimize the LMP90xxx’s offset and gain errors.

–

The last known offset or gain calibration coefficients can come from two sources. The first source is the

default coefficient which is pre-determined and burnt in the device’s non-volatile memory. The second

source is from a previous calibration run of Type 1: Correction.

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