Datasheet

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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