RFID chip power output will impact – or even limit – how simple or complicated your solution design will be in terms of supplying power to your selected device.

We’ve been discussing about different features your selected RFID chip should have for your new battery free RFID solution.

Topics such as SPI communication, sensitivity or a battery switch (for BAP solutions) are important but RFID chip power output to supply your desired device is key.

In general you will want to use devices with the lowest power consumption possible. That will typically lead you to sensors, actuators, microcontroller and a bunch of other components that work at low voltages.

However, how low is your ‘low voltage supply’?

RFID chip power output to cover a wide range

Strategic thinking in solution portfolio development is important. Even though you may be thinking about developing a specific battery free sensor tag – let’s say a battery free temperature sensor solution – you may end up designing other types of similar solutions – such as battery free relays for example.

Note that you may find different types of devices you want to work with. These devices will typically require different supply voltages to work:

  • Digital sensors. You can find temperature, pressure or humidity sensors here for example.

Following the power consumption trends for smartphone usage, these sensors are very low power and can usually work at 2.5V, 1.8V or even at 1.2V, which is great for battery free RFID solutions.

  • Analog sensors. There are a myriad of sensors in this group from temperature to strain gages.

There is a high variability in this group but 3.3V to 5V are considered typical here. The key to understand how to work with them is that these voltages are actually recommendations by the manufacturer but it doesn’t mean they won’t work at lower voltages. It may just be a little bit more complicated to get the correct measurements from them – may require specific signal conditioning circuits (remember, low power!)

  • Microcontrollers. You may want to perform specific commands in your solution. Microcontrollers allow you to design more complex solutions at the cost of complicating the design of the tag.

You can find microcontrollers working at 2.5V to 3.3V in general.

Of course, there are more devices you may want to use such as displays, actuators, LEDs, etc. Just by looking at the ones mentioned, you can already see where I’m heading: 1.2V to 3.3V is a wide range.

Does your RFID chip power output cover that range?

The first thing is making sure the RFID chip you select covers a good range. The ideal range will depend on the solutions you have in mind but 1.2V to 3.3V is considered a very broad one if parameters such as sensitivity are good for this range.

As discussed in a previous post, sensitivity of the chip is affected by the voltage level the chip has to work at so there’s always a complex trade off in terms of power consumption and power output availability.

Configuring the power output level – voltage regulators

On top of having a good range, there’s the issue of being able to fix the power output to a specific voltage level. This needs to be correct so that your devices work as they are expected to.

With a range from 1.2V to 3.3V you’re probably going to run into many issues with most digital sensors and microcontrollers, as well as many other electronic components.

You will have to design a startup circuit to actually supply the power your devices require. This typically involves some sort of storage device (capacitor) and some kind of regulator to provide the voltage level the circuits need. When the voltage is below that value, your design will have to open the circuit so that the capacitor can be charged again for a new action.

Some RFID chips will embed this. You will just have to use the regulators giving you a specific voltage level.

The next step are RFID chips that can configure the RFID chip power output to your desired voltage level. No fixed regulators but configurable within the chip output voltage range.

It obviously saves time and resources having these in mind when selecting the proper RFID chip so make sure you think ahead and figure out what your needs will be in the future!