5

4688D–RFID–03/07

U3280M

3.2.1

Digital Input to Control the Damping Stage (MOD)

MOD = 0: coil not damped

MOD = 1: coil damped

V

Note:

If the automatic power management is disabled, the internal front-end V

this case the value V

3.3

Field Clock

The field clock extractor of the interface makes the field clock available for the microcontroller. It

can be used to supply timer inputs to synchronize modulation and demodulation with the field

clock.

3.4

Gap Detect

The transponder interface can also receive data. The base station modulates the data with short

gaps in the field. The gap-detection circuit detects these gaps in the magnetic field and outputs

the NGAP/field signal at the NGAP pin. A high level indicates that a field is applied at the coil

and a low level indicates a gap or that the field is off. The microcontroller must demodulate the

incoming data stream at one of its inputs.

V

coil-peak

V

DD

2V

CMS

V

CU

=

+

×

=

V

coil-peak

V

DD

2

×

V

CD

==