AN3250 Datasheet, PDF (6/16 Pages) STMicroelectronics – M24LR64-R Multi-bank reference design description and settings

Designing an M24LR64-R multi-bank application
AN3250
As the antenna tuning frequency (f_TUNING) must remain at 13.56 MHz, designers must
decrease the antenna inductance by the same factor as the increase of the tuning
capacitance of a multi-bank circuit:
L_{MULTI_BANK} = L_INDUCTOR / n
In the following example, four M24LR64-R devices are connected in parallel on the same
antenna. The inductance value of this antenna must be four times smaller than the one used
for a single M24LR64-R.
As a reference, Figure 6 represents a single antenna single M24LR64-R device as per
STMicroelectronics ANT1-M24LR-A reference design.
Figure 6. Block diagram for ANT1-M24LR-A reference design
The ANT5-M24LR-A reference design (Figure 7) consists of four M24LR64-R devices in
parallel, resulting in 256 Kbits of equivalent user memory. The equivalent tuning capacitance
value is 4 times that of a single M24LR64-R device. So the antenna, whether it is designed
on a PCB or uses an SMD inductor, must be 4 times smaller than the one used for one
single M24LR64-R device.
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Doc ID 17761 Rev 1