Is Ground Electrically Isolated From the Cheetah SPI Host Adapter when I Apply External Power to the SPI Device?

 Cheetah SPI Host Adapter

Question from the Customer:

I understand the Cheetah SPI Host Adapter comes with the option of using either an external power supply or the Cheetah adapter (with power from the USB bus I assume) to drive the SPI output.

My question is about ground - if I am using an external power supply to drive the SPI device output, is the ground from the external power supply electrically isolated from the USB ground on the other end of the Cheetah adapter?

I also have questions about connecting power.

  • Is the 5V pin on the SPI side of the Cheetah an output pin or an input pin?
  • On the Cheetah PCB, there is a 5-pin component labeled DN401. What is this component? Is it possible to replace it?

Response from Technical Support:

Thanks for your questions! The following sections provide the information that you requested.

 

Grounding External Power

The USB and SPI sides on Cheetah adapter are not galvanically isolated as they share a common ground. For the best results, we recommend tying the ground pins of the target system to the Cheetah adapter ground pins.

 

Power Pins on the Cheetah Adapter

Pins 4 and 6 are output pins – they provide power with the voltage level of 5V to target boards or chips.

 
Cheetah SPI Host Adapter Power Pins

For more information about the pins and related signals, please refer to the Connector Specification of the Cheetah SPI Host Adapter User Manual.

 

ESD Protection Diode

The component, DN401 is an ESD protection diode for SS1/SS2 lines. The DN401 can be replaced with a new NSQA6V8AW5T2G part from ON Semiconductor.

For more information about power consumption and related specifications, please refer to the section Signal Specifications / Power Consumption of the Cheetah SPI Host Adapter User Manual.

Additional resources that you may find helpful include the following:

More questions? More projects? You can contact us at sales@totalphase.com. You can also request a demo that applies to your application.

Request a Demo