U3280M_07 Datasheet, PDF (5/21 Pages) ATMEL Corporation – Transponder Interface for Microcontroller

U3280M
3.2.1
Digital Input to Control the Damping Stage (MOD)
MOD = 0: coil not damped
V_coil-peak = V_DD × 2 + V_CMS = V_CU
MOD = 1: coil damped
V_coil-peak = V_DD × 2 = V_CD
V_CMS = V_CID: modulation voltage stroke at coil inputs
Note: If the automatic power management is disabled, the internal front-end V_DD is limited at V_DDC. In
this case the value V_DDC must be used in the above formula.
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.
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4688D–RFID–03/07