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[#1]

5V or 3.3V I/O supply for S32k3

Hello everyone,

I'm currently designing an automotive ECU based on the NXP S32K3 family and I'm evaluating the best configuration for the MCU I/O supply domains.

As I understand, the device allows different supply options for I/O Domain A and Domain B, such as:

• Domain A = 5 V, Domain B = 5 V
• Domain A = 3.3 V, Domain B = 3.3 V
• Domain A = 5 V, Domain B = 3.3 V

I'm trying to understand the main design trade-offs and selection criteria for each configuration. Specifically:

1. What are the key advantages and disadvantages of using 5 V versus 3.3 V on the I/O domains?
2. In which automotive applications is a mixed-voltage configuration (5 V / 3.3 V) typically preferred?
3. Are there implications regarding EMC/EMI performance, power consumption, signal integrity, robustness, or interface compatibility that should drive this choice?
4. Does NXP provide any application note, hardware design guideline, or reference document explaining the rationale and recommended use cases for each I/O supply option?

I would appreciate any design recommendations or lessons learned from previous S32K3 projects.

Thank you!

Re: 5V or 3.3V I/O supply for S32k3

Hello @DavidSilva,

Rather than advantages and disadvantages, this mainly depends on your application's requirements. You can configure VDD_HV_A & VDD_HV_B domains depending on your system's voltage level, as well as your device's interface modules. This means that trade-offs and preferences are based solely on your design.

The biggest impacts would be:

1. VREFH should always be equal to or less than VDD_HV_A +0.1. Any positive differential voltage between VREFH and VDD_HV_A i.e., VDD_HV_A < VREFH <= VDD_HV_A + 0.1V) is for RF-AC only.
2. LPCMP0 channels must only be selected/enabled when VDD_HV_A >= VDD_HV_B. These channels must be disabled when VDD_HV_A goes below VDD_HV_B.

The internal team has also shared that we do not provide current consumption values for 3.3V specifically, as this is essentially the same as 5V, you can use 5V measurements.

We also do not provide an application note specifically discussing voltage domain configurations, however, you can refer to the HW Design Guidelines application note, which goes over all of the requirements and recommendations for S32K3 (including voltage domains).

Best regards,
Julián