S32K311 LCU Rise/Fall Filter Deadtime Occasionally Reduced from 2 µs to 1 µs

Esakki — Sat, 01 Aug 2026 07:00:27 GMT

Hi NXP Team,

I am using an S32K311 with RTD 5.0.

The PWM signals are generated by eMIOS0 and routed directly to the LCU0 outputs:

eMIOS0_CH0 -> LCU0_OUT0

eMIOS0_CH1 -> LCU0_OUT1

eMIOS0_CH2 -> LCU0_OUT2

eMIOS0_CH3 -> LCU0_OUT3

eMIOS0_CH4 -> LCU0_OUT4

eMIOS0_CH5 -> LCU0_OUT5

The LCU is configured to insert deadtime using the Rise/Fall Filter.

Configuration

MCU: S32K311
RTD Version: 5.0
PWM source: eMIOS0
Deadtime generation: LCU Rise/Fall Filter
Rise Filter on Highside Channels = 192
Fall Filter on Lowside Channels = 192
Configured deadtime = 2 µs

Observed behavior

Most switching events generate the expected 2 µs deadtime.

However, occasionally one transition (either the rising edge or the falling edge) has only about 1 µs deadtime instead of 2 µs. This occurs intermittently while the PWM frequency and duty cycle remain unchanged.

The attached logic analyzer capture shows this behavior.

Questions

Is this variation expected when using the LCU Rise/Fall Filter?
Are there any synchronization requirements between the eMIOS outputs and the LCU filter?
Can the LCU filter occasionally shorten the programmed delay due to internal synchronization or clock-domain crossing?
Is there any known limitation or errata related to the Rise/Fall Filter on the S32K311?

Any guidance would be appreciated.

Thank you.

Re: S32K311 LCU Rise/Fall Filter Deadtime Occasionally Reduced from 2 µs to 1 µs

Senlent — Mon, 03 Aug 2026 08:34:13 GMT

Hi@Esakki

Your value 192 = 2 µs implies an LCU filter tick of about：

2us / 192 = 10.4167 ns

-> 1/ 10.4167 ns = 96MHz,

If the effective LCU/peripheral clock or prescaler changes, or if a different clock is selected than assumed, the real delay changes.

2.Using an oscilloscope for testing is more accurate, and the waveform is related to the external capacitive reactance; a large capacitive reactance can also cause waveform instability.

topic Re: S32K311 LCU Rise/Fall Filter Deadtime Occasionally Reduced from 2 µs to 1 µs in S32K

S32K311 LCU Rise/Fall Filter Deadtime Occasionally Reduced from 2 µs to 1 µs

Re: S32K311 LCU Rise/Fall Filter Deadtime Occasionally Reduced from 2 µs to 1 µs