NXP Semiconductors
FXPS7115D4
Digital absolute pressure sensor, 40 kPa to 115 kPa
7.3.4 Digital signal processor (DSP)
A DSP is used to perform signal filtering and compensation. A diagram illustrating the
signal processing flow within the DSP is shown in Figure 6.
USER OFFSET
AND
SINC
FILTER
IIR
LPF
Σ
= Y(Z)
TRIM
P
ABS
OUT
GAIN ADJUST
aaa-029737
Figure 6.ꢀSignal chain diagram
7.3.4.1 Decimation sinc filter
In Equation 2, the output of the ΣΔ modulator is decimated and converted to a parallel
value by two third-order sinc filters; the first with a decimation ratio of 24 and the second
with a decimation ratio of 4.
(2)
aaa-023449
20
magnitude
(dB)
0
-20
-40
-60
-80
minimum
typical
-100
maximum
-120
3
4
5
10
10
10
frequency (Hz)
Figure 7.ꢀSinc filter response
7.3.4.2 Signal trim and compensation
The device includes digital trim to compensate for sensor offset, sensitivity, and
nonlinearity over temperature.
7.3.4.3 Low-pass filter
Data from the sinc filter is processed by an infinite impulse response (IIR) low-pass filter
with the transfer function and coefficients shown in Equation 3.
(3)
FXPS7115D4
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© NXP B.V. 2019. All rights reserved.
Product data sheet
Rev. 3 — 5 December 2019
9 / 72
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