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How Do I Set the Target Level Supply Voltage for an SPI Device for less than 3.3V using the Promira Serial Platform?
Rena Ayeras

Question from the Customer:

I am testing SPI slave memory chips on an in-house test board. Some of the products we design have voltage specifications of 1.2V or 1.8V VCC and VCCIO.  Can the Promira Serial Platform source target devices at those levels? My current understanding, the VCC target supply is limited to 3.3V or 5V. Is there a way to source the target 1.2V or 1.8V as needed?

Thinking ahead, it would be great to be able to seamlessly program VCC as well as VCCIO from 0.9V to 3.6V.

Response from Technical Support:

Thanks for your question! The Promira Serial Platform is very flexible and can be set up for the VCC and VCCIO levels that you desire. Following is an overview of Promira platform’s level shifting capabilities, followed by details about signal and target supply voltage levels.

Overview of Level Shifting

The Promira platform offers integrated level shifting for I2C and SPI. This makes it capable of communicating with devices at a range of voltages from 0.9 to 5.0 volts, without the cost and time of using external accessory boards.

You can control these levels with either the Control Center Serial Software or the Promira Software API.

Promira Serial Platform Power Source Pins

Two pairs of target power sources are provided with the Promira platform:

  • VCC pins 4/6, which can be set for 3.3V or 5V
  • VIO pins 22/24, which can be set within the range 0.9V - 3.45V
  • Using the “internal supply” of the Promira platform, the power regulator sources pins 22/24, up to 200 mA can be provided to the target device. If more current is needed, we recommend using  the wall adapter to source power.
  • Note – by default, the target power pins are unconnected at the time of shipping. The power pins can be enabled with the Control Center Serial Software.

For more information about enabling the pins and setting the levels, please refer to sections Powering Downstream Devices and Shifting Logical Level in the Control Center Serial Software User Manual.

For information about API commands, please refer to the section API Documentation in the Promira Serial Platform I2C/SPI Active User Manual


Available Target Power

The Promira Serial Platform can be powered via USB to the host computer or via wall outlet.    The available target power  depends on the power source.  The USB protocol limits how much power can be provided on the bus.  USB 2.0 connections can provide up to 500 mA, while USB 3.1 connections can provide up to 900 mA.  Please keep in mind this is the amount power available to the entire USB system.  Using our wall adapter to source power, your ability to provide target power will not be limited by the USB bus.

We hope this answers your questions. Additional resources that you may find helpful include the following:

We hope this answers your question. Need more information? You can contact us and request a demo that applies to your application, as well as ask questions about the Promira Serial Platform and other Total Phase products.