nrf5340 SPIM GPIO drive strength

[Frikkie Badenhorst]

Hi there,

We are currently implementing SPIM on the nrf5340. From the NRF5340 Product Specification, in the electrical specifications section of the SPIM peripheral, it is stated that for higher bit rates, a higher drive configuration should be used, and then refers to the GPIO section.

Firstly, what is considered high bit rates? In other words, when should we use High drive and when can we use a lower driver configuration?

Secondly, is there some documentation on what exactly the different drive strengths mean? The documentation is very vague

Kind regards,

Frikkie

[Naeem Maroof]

Hello

High bitrate here means higher than 8Mbps, and that is SPIM4 instance in nRF5340 that supports beyond 8Mbps and up-to 32Mbps.

(from table 146 of the product specification)

Drive strength signifies how fast and how much current could be supplied or sinked using the specified pin.

So, it is equivalent to turning on multiple transistors in parallel from VDD to the node, or from the node to the ground.

Turning multiple transistors ON (in parallel) improves the drive strength (meaning: can provide more current) and would reduce the resistance, and therefore steeper rise and fall times.

snippets from GPIO electrical specification (of nrf5340 product spec):

/BR, Naeem