Design Strategy for Complementary PWM Generation for motor driver Using eMIOS and LCU on S32K344

[Ayaz]

Design Objective

I am developing a motor control system using the S32K344 microcontroller. The system is designed to control a motor driver via PWM signals applied to both IN1 and IN2 , enabling control of both the direction and speed of the motor. A key requirement is to ensure that current feedback (motor current) is sampled by the ADC only during the ON period of the PWM cycle on both IN1 and IN2.

My Questions

1- Is OPWMCB Mode the Most Suitable Option for PWM Generation?

I am considering using the eMIOS module in OPWMCB (Output Pulse Width Modulation Center-Aligned Buffered) mode to generate complementary PWM signals with built-in dead-time insertion. This approach appears well-suited for driving both IN1 and IN2 in a synchronized and safe manner.

2- Can eMIOS alone generate complementary PWM signals without LCU intervention?

My understanding is that a single eMIOS channel in OPWMCB mode (specifically EMIOS_PWM_IP_MODE_OPWMCB_TRAIL_EDGE) can generate both the primary and complementary PWM signals, and that the same channel can be used to trigger ADC conversion at the center of the PWM cycle to obtain current feedback.

I would like to confirm how this can be achieved in practice. I have attempted to implement this, but it is not functioning as expected. I have attached my project for review.

3- Is it only possible to generate complementary PWM using the LCU?
If eMIOS cannot generate complementary PWM signals independently, is the LCU required to implement this functionality?

4- Using eMIOS for Independent PWM Channels
As an alternative, I am also considering using two separate eMIOS channels to generate independent PWM signals for IN1 and IN2. However, I would like to understand how to synchronize these channels effectively to avoid timing mismatches or shoot-through conditions. Since both channels would share the same period and time base, would that be sufficient?

4- Most Important Requirement: Triggering ADC Conversion at the Center of OPWMCB?

I would like to use the same PWM signal for both IN1 and IN2 to trigger the ADC for sampling current feedback during the ON period of the PWM cycle.

• How can this be achieved?
• Which PWM mode is best suited for this purpose?
• Can this be done using eMIOS OPWMCB mode, or is another configuration more appropriate?

[_Leo_]

Thank you for your interest in our products and for contributing to our community.

Regarding your questions:

1. They are various ways to archive complementary PWM outputs with dead-time insertion using eMIOS (with or without LCU), the OPWMCB mode is one of this ways.
2. Without LCU you need two eMIOS channels in OPWMCB mode for complementary outputs using the polarity parameter, and a third one for ADC triggering.
3. From my opinion, eMIOS->TRGMUX->LCU is the best way for complementary outputs, because you only need one eMIOS channels instead, which means that you only have to update the duty cycle to one channel.
4. Synchronization is only achievable for channels that share the same time base.
5. Triggering support is available via flag generation, for the OPWMB, DAOC, OPWMCB, and OPWFMB modes is on rising and/or falling edges. The OPWMT mode is the most flexible for this feature, which allows trigger at any moment of the period time, using Trigger parameter.

My suggestion is to use eMIOS(OPWMB)->TRGMUX->LCU for complementary PWM outputs with dead-time insertion and OPWMT for ADC triggering, both eMIOS channels (OPWMB and OPWMT) sharing the same time base.

For more details, please refer to the following knowledge base post:

• S32M27x/S32K3 – eMIOS/TRGMUX/LCU – [RTD600] -> https://community.nxp.com/t5/S32M-Knowledge-Base/S32M27x-S32K3-eMIOS-TRGMUX-LCU-RTD600/ta-p/2163968
• S32M27x/S32K3 – eMIOS/BTCU/ADC/DMA – [RTD600] -> https://community.nxp.com/t5/S32M-Knowledge-Base/S32M27x-S32K3-eMIOS-BTCU-ADC-DMA-RTD600/ta-p/215554...

Additionally, please check 6.6. PWM design considerations section of the following post, which deeps into supported features across PWM modes:

• S32M27x/S32K3 – eMIOS Usage -> https://community.nxp.com/t5/S32M-Knowledge-Base/S32M27x-S32K3-eMIOS-Usage/ta-p/2129760

I hope this information is helpful.

[Ayaz]

I would like to avoid using the LCU.

My goal is to configure two eMIOS PWM channels in OPWMCB mode to control IN1 and IN2 for speed and direction control at 40 kHz (25 µs period).

Additionally, I want to configure a third eMIOS PWM channel in OPWMT mode, offset by 12.5 µs, to consistently trigger ADC sampling at the midpoint of the IN1/IN2 PWM period.

However, the timebase for the eMIOS channels used for IN1 and IN2 cannot be shared with the eMIOS channel used for ADC triggering, since they operate in different modes (OPWMCB vs OPWMT).

My questions are:

• If all the timebases are configured within the same eMIOS instance, can they still be synchronized?
• Is synchronization only possible by enabling the Global Time Base (GTB) in MCL?
• My main goal is to ensure that the ADC samples once per PWM period, precisely when either IN1 or IN2 is active.

How can I achieve this design, or do you have any alternative suggestions?

[_Leo_]

Use OPWMCB mode for complementary (center-aligned) PWM outputs and OPWMT for trigger at half the time high is not possible for the following reasons:

• Triggering support is only available via flag generation.
• Synchronization is only achievable for channels that share the same time base.
  • The OPWMCB mode needs to be clocking by another eMIOS channel (MCL driver) in MCB_UP_DOWN_COUNTER, as time base.
  • The OPWMT mode needs to be clocking by another eMIOS channel (MCL driver) in MC_UP_COUNTER or MCB_UP_COUNTER, as time base.

Instead trigger at half the time high with OPWMT, it can be triggered by the MCB mode in UP/DOWN Counter, like the approach in [RTD400 LLD]K344 Center Aligned PWM Trigger ADC BCTU.

But consider following limitations:

• For OPWMCB mode: it can be only implemented eMIOS channels type G (eMIOS0: ch1-7).
• For MCB mode in UP/DOWN Counter: It has 2 flags, not only at the center.

For my part, I continue to recommend my previous suggestion.

Have a nice day!