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1

fres

2 *

* L * Cchip

=

p

Qc * Ql

Qres

Qc

Ql

=

+

L

Z

Qres *

Cchip

=

0

7.5

15

22.5

30

37.5

45

52.5

60

0

3125

6250

9375

1.25 .10

4

1.56 .10

4

1.88 .10

4

2.19 .10

4

2.5 .10

4

Znom QL

(

)

Zmin QL

(

)

Zmax QL

(

)

QL

Recommended

operating range

QC=80

Antenna Calculation

Resonance

frequency:

Total quality factor:

Input impedance:

Based on an IC capacitance of 23.5 pF, the impedance shall be matched to be in the specified impedance

range of 6.5 to 15.5 k

Ω to fit the IC capabilities.

Note:

If Z > 15.5 k

Ω, reduced performance of read range must be considered.

Table 3-4. Antenna System Parameters

Tolerance

Parameter

Min

Nom

Max

Test conditions

Comment

[%]

Cchip [pf]

21.15

23.5

25.85

10

13.56 MHz @ 2 Vrms

Qchip

80

100

120

20

L [

μH]

5.74

5.86

5.98

2

13.56 MHz @ 2 Vrms

QL

15

40

44

10

fres [MHz]

12.8

13.56

14.44

Qres

12.63

28.57

32.2

Z [k

Ω]

6.58

14.27

15.48

Figure 3-9. Recommended Operating Range – Impedance vs Antenna Q

SCBU045 (11-09-21-065) – October 2007

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