Rocky100 major improvements: Battery Assisted Passive mode
We already hinted that the Rocky100 chip can work in Battery Assisted Passive (BAP) mode when we were discussing sensitivity. We mentioned the Rocky100 sensitivity was -24dBm and -35dBm, depending on the BAP you configure for a specific solution.
In the past, our idea with the ANDY100 was to allow engineers to develop completely battery free solutions with external devices. The ANDY100 does not implement a battery assisted passive mode option to increase communication range.
Over time, the feedback from developers has been towards increasing the sensitivity of the tag for passive performance but there have been multiple requests to increase read range even if they have to use batteries for that.
One thing I’d like to clarify is that using a battery on an RFID tag does not always mean BAP. We have had cases in the past where:
- Power consumption of the sensor was too high. This means the ANDY100 could not power up the device so the tags would never work.
The customer agreed on using batteries on the tag. They did not need to increase the communication range – 1.5 meters was good enough for their application – but they needed to power up the device.
In these cases, you can design a circuit with a battery to power up just the external device (and its required circuitry). This means the RFID chip runs without load, giving you its best sensitivity in completely battery free mode.
- Data logging capabilities. Data logging requires the sensors to take measurements even when they are not close to an RFID reader
Once again, the customer was happy to include batteries on the tag and the read range was good enough for their application.
In this case, you can also work with a design in which the battery only powers up the data logging circuit – sensor, memory and controller – leaving the RFID tag work without load.
When developing the new Rocky100, we realized it would be better to give the option to the developer. It’s you as the developer to decide whether you prefer to connect the battery only to the external circuit or connect it to the RFID chip too so you can have a longer read range – but also a higher power consumption!
On top of that, to enhance the battery assisted passive feature of the Rocky100 chip, we have implemented a battery switch. The battery switch connects/disconnects the battery from the chip by means of a digital command – either from the RF interface or the SPI interface.
The idea behind the battery switch is to make it easy for you to assemble the battery anytime you want but only connect to the chip whenever you like. This way you can save battery life while your tags are in the warehouse and activate the BAP mode only when they are sent to the customer for use.
See below a couple of graphs with the leakage current vs. battery voltage and the dropout voltage vs. load current consumption.
Rocky100 major improvements: detailed characteristics of VBAT switch
On the BAP mode itself, the Rocky100 goes from -14dBm sensitivity to -24dBm in the BAP mode. You can also configure an enhanced battery assisted passive mode (EBAP) to get -35dBm at the cost of 2uA extra power consumption.
Remember that, as we already explained in the sensitivity section, the BAP sensitivity only applies to the chip, not the complete system. The fact that the chip sensitivity goes up to -35dBm does not imply that the reader on the other side can receive the signal due to how backscattering works – signals traveling longer will become less powerful, compromising the ability of the RFID reader to receive them correctly.
As always, it’s your duty to decide whether you really need the extra read range for your solution or the extra power consumption from the BAP mode will reduce your battery life too much. The Rocky100 gives you the possibility to configure the tag at your will.