NBP8 datasheet(20/58 Pages) NXP

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NXP Semiconductors

NBP8

Battery pressure monitor sensor

The different variables and thresholds correspond to the following:

• Pcurrent: variable internal to the NBP8 program that holds the latest pressure

measurement. Pressure measurements are taken at a sample rate configured by the

user.

• Pprevious: variable internal to the NBP8 program that holds the previous pressure

measurement.

• PrefST: variable internal to the NBP8 program that stores the last pressure value before

the pressure started to rise.

• t: 16-bit variable internal to the NBP8 that is incremented periodically at the pressure

sample rate when the pressure has been rising (that is, when Deb_ST_cnt is greater

than 0) to keep track of the number of sampling periods during which pressure has

been rising.

If t value reaches its maximum value 65535, the pressure has been increasing over the

last 65535 sampling periods but the Debounce counter has not reached the Debounce

threshold. Reaching a t value of 65535 only happens if the Debounce threshold is set

to a very high value and pressure increases extremely slowly. When such a situation

occurs, the process resets in order to avoid rollover and a potentially incorrect slope

calculation.

• Min_T: user-configurable threshold that defines the minimum number of counts by

which the current pressure value must exceed the previous pressure value, for the

NBP8 program to consider that the pressure is rising. The value is stored in PCMINT

• Deb_ST_cnt: counter internal to the NBP8 program updated every time a new pressure

measurement is taken. The counter is incremented if the pressure is considered to be

increasing, following the condition described above. It is decremented otherwise. When

the counter reaches 0, it cannot be further decremented.

• Debounce_T: user-configurable threshold. The value is stored in PCDEBT register.

When the value in Deb_ST_cnt exceeds this threshold, the pressure increase is

considered consistent and the slope of pressure versus time is calculated to check

whether the pressure increase should be notified to the external host.

• Slope: variable internal to the NBP8 program that holds the value of the scaled slope

(Pcurrent - Pref) * 128 / (t+1).

The coefficient 128 provides improved precision in the slope calculation since all

calculations are computed with integer values. Examples of slope calculation are

provided in the description of the PCSLOPETH/L registers.

• Slope_T: user-configurable threshold. The value is stored in PCSLOPETH/L registers.

When the value in Slope exceeds this threshold, the pressure increase is considered

significant and the NBP8 raises the Pressure Change Detection flag before notifying to

the external host that an event requiring attention occurred.

Figure 14 shows an example algorithm execution. In this example, the sample rate is set

to 50 ms. The Pressure FIFO depth is 12 measurements; the gray dots represent the

pressure values not available in the FIFO anymore when the flag is raised; the black and

green dots represent the pressure values available in the FIFO when the flag is raised;

the green dot represents the latest pressure measurement added to the FIFO when the

flag is raised.

NBP8

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 2.4 — 11 March 2022

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