Tuning capacitance dependency for using the same antenna design

AN4409

4/8

DocID025583 Rev 1

Equation 2

Equation 3

Dividing Equation 2 by Equation 3 leads to:

Equation 4

or, after simplification, to Equation 5:

Equation 5

Respecting the tuning frequencies defined in section 1) leads to the following relationship:

The M24SRXX-Y and M24LRXXE-R internal tuning capacitance has been designed

following this rule offering to customers a simple way to use the M24LRXXE-R or

M24SRXX-Y Dual Interface EEPROMs in their application without changing their antenna

design.

f

1

2

M24LR

⋅

------------------------------------------

=

M24SR

1

2

M24SR

⋅

------------------------------------------

=

M24LR

M24SR

---------------------

2

M24SR

⋅

2

M24LR

⋅

------------------------------------------

M24SR

M24LR

-------------------

==

M24SR

M24LR

-------------------

M24LR

M24SR

---------------------

⎝⎠

⎜⎟

⎛⎞

2

=

M24SR

M24LR

-------------------

13.8MHz

14.2MHz

-------------------------

⎝⎠

⎛⎞

2

0.94

≅

=