NXP Semiconductors UM11227 - SMI Signal Measurement Modes

NXP Semiconductors
UM11227
NTM88 family of tire pressure monitor sensors
UM11227 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2020. All rights reserved.
User manual Rev. 6 — 24 April 2020
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aaa-031064
CH. 0 AND 1
T/R
CLOCK
GEN
CH. 0 AND 1
M
CH. 0 AND 1
B/L
Cs
p-CELL
P
Z
X
Cm
Cr
CELL
SELECT
C TO V
CONV
POWER
CONTROL
MODE
CNTL
SMI
SOFT
BLOCK
SMI_IPI_INT
SMI_EN
IPP_MFO
IPG_CLK
IPS_ADDR
IPS_WDATA
SMI_IPS_RDATA
MFOEP
MFOELF
MFOE
IPS_RWB
AMP
GAIN
TRIM
OFFSET
AND
POLARITY
TRIM
PARITY
CHECK
MUX
C2V hardblock
SFO
SSEL[1:0]
SMI_ADC_TRIGGER
f
MFO
SMI_VOUT3
ipp_ind_mfo_clk
smi_mfoea
PARITY
BIT
2ND
GAIN
BUFFER
PTA3
MFO
125 kHz
SWITCH
ST_DRV
SELF TEST
SST
STST
ATB0
PTB0
ADC10
RST_B
g-CELL
The digital circuitry in the C2V hard-block is continuously powered by V
DD
Figure 44. Sensor measurement interface block diagram
10.19.1 SMI signal measurement modes
In the sensor signal measurement mode, the transducer (g-cell or p-cell) and its interface
circuit are powered up and the resulting analog voltage appears at the ADC after some
time delay. This process can be automatically triggered or controlled directly by the MCU.
The signal measurement mode provides three sub-modes:
• Automatic where the internal hardware circuits control a singular measurement
(transducer voltage capture and ADC conversion trigger).
• Direct where the software application controls a series of measurements (sequence of
transducer voltage captures and the ADC conversion triggers).
• Low power direct (LPDM) where the software application sets up the initial and
subsequent settling times, and then the internal hardware circuits control the series of
measurements.
Table 145 summarizes the compatibility of the SMI measurement modes with the MCU
operational modes. Since the SMI is disabled during STOP1, the SMI cannot be used
when the MCU is in STOP1. All modes are available when the MCU is in RUN mode,
although higher noise or offset may be observed. Therefore STOP4 is recommended
for highest accuracy. When in the automatic mode, the user application (MCU in Run)
controls the trigger of the measurement via the SEN bit. When in the direct modes, the
user application (MCU in Run) controls the trigger of the ADC via the SCAP bit. If the
application intends a period of Stop4 between the SMI completion and the subsequent