FS2302M datasheet(62/230 Pages) NXP

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NXP Semiconductors

FS23

Safety system basis chip (SBC) with power management, CAN FD and LIN transceivers

The LDT_SEL bit allows the MCU to either set/read the wake-up target value or to read the current value of the

24 bit LDT counter in the LDT_WUP_H[7:0] and the LDT_WUP_L[15:0] bits.

• When LDT_SEL = 0, the MCU can read or write the wake-up target value in the LDT_WUP_H[7:0] and the

LDT_WUP_L[15:0] bits.

• When LDT_SEL = 1, the MCU can read the counter current value (running or not).

The LDT_EN bit is provided to start the LDT timer operation:

• When LDT_EN = 0, the LDT is disabled.

• When LDT_EN = 1, the LDT starts counting as defined in the M_LDT_CTRL and M_LDT_CFGx registers.

The LDT2LP bit selects which Low-power mode (LPON or LPOFF) it needs to go once the after-run timer is

expired, when timer function 2 or 3 is selected.

• When LDT2LP = 0, the device goes into LPOFF mode when the after-run timer expires.

• When LDT2LP = 1, the device goes into LPON mode when the after-run timer expires.

• When timer function 4 or 5 is selected and the LDT_EN = 1, the LDT does not start any count until the device

enters the corresponding Low-Power mode.

17.1 Calibration procedure

The calibration principle consists of activating the counter for a specific duration and comparing the timing given

by the LDT with the MCU's accurate clock and timing. Once the timer expires, the MCU reads back the final

timer value and compares it that value with its own accurate time of activation to calculate a time offset. It is

recommended to perform the calibration between -20 °C and 85 °C.

Calibration example:

1. Set the Timer mode to short count. Select the timer function 1. Set the after-run value at 65535 (~8.4 s).

2. Start the counter.

3. Read the counter when the MCU RTC reaches 7 s (must be less than 7.5 s with ±10.0 % oscillator

accuracy).

4. If the oscillator period is at the exact typical value (absolutely no deviation error), the expected reading is

54688.

5. The exact reading is used to compute the error correction factor ECF = exact_reading/expected_reading.

• ECF < 1 if the oscillator is faster than the exact typical value.

• ECF > 1 if the oscillator is slower than the exact typical value.

After calibration, the new after-run or wake-up values to set the counter are “after run x ECF” and “wake-up x

ECF”.

FS23

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

Product data sheet

Rev. 7.0 — 16 October 2024

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FS2302M Scheda tecnica(PDF) 62 Page - NXP Semiconductors