EM4095

Copyright

 2002, EM Microelectronic-Marin SA

10

www.emmicroelectronic.com

Appendix

Equations

f

LC

A

0

0

1

2

=

π

(1)

CC

CC

CC

RES

DV

DV

DV

DV

0

12

12

=+

∗

+

(2)

following equation:

R

fL

Q

ANT

A

A

=

2

0

π

(3)

The equations which follow are valid for bridge

configuration as defined on Figures 1, 2 and 3. For figures

The AC current amplitude at resonant frequency is

defined as follows:

I

VV

RR

R

ANT

dd

ss

ANT

SER

AD

=

−

++

4

2

π

(4)

RMS antenna current (important for power dissipation

calculation):

I

I

RMS

ANT

=

2

(5)

Peak to peak voltage on antenna is defined by following

equation:

0

f

I

V

ANT

ANTpp

π

=

(6)

To ensure correct operation of the AM demodulation

chain, the AC peak to peak voltage on DEMOD_IN pin

peak to peak voltage on antenna is known the capacitor

divider division factor can be calculated:

2

1

1

_

DV

DV

DV

ANTpp

INpp

DMOD

C

C

C

V

V

+

=

(7)

Power dissipation is composed of power dissipated on

ANT drivers and internal power consumption:

()

PI

R

I

V

V

RMS

AD

DDon

DD

SS

=⋅

⋅

+

−

2

2

(7)

Temperature increase of die due to power dissipation is:

Th

R

P

T

⋅

=

∆

(8)

© EM Microelectronic-Marin SA, 07/02, Rev. Ê/490

EM Microelectronic-Marin SA cannot assume responsibility for use of any circuitry described other than circuitry

entirely embodied in an EM Microelectronic-Marin SA product. EM Microelectronic-Marin SA reserves the right to

change the circuitry and specifications without notice at any time. You are strongly urged to ensure that the

information given has not been superseded by a more up-to-date version.