U2270B_08 Datasheet, PDF (9/18 Pages) ATMEL Corporation – Read/Write Base Station

U2270B
3.7 Driver (DRV)
The driver supplies the antenna coil with the appropriate energy. The circuit consists of two inde-
pendent output stages. These output stages can be operated in two different modes. In common
mode, the outputs of the stages are in phase; in this mode, the outputs can be interconnected to
achieve a high-current output capability. Using the differential mode, the output voltages are in
anti-phase; thus, the antenna coil is driven with a higher voltage. For a specific magnetic field,
the antenna coil impedance is higher for the differential mode. As a higher coil impedance
results in better system sensitivity, the differential mode should be preferred.
The CFE input is intended to be used for writing data into a read/write or a crypto transponder.
This is achieved by interrupting the RF field with short gaps. The various functions are controlled
by the inputs MS and CFE (see “Function Table” on page 10). The equivalent circuit of the driver
is shown in Figure 3-1 on page 4.
Figure 3-9. Equivalent Circuit of Pin MS
30 µA
MS
Figure 3-10. Equivalent Circuit of Pin CFE
30 µA
4684E–RFID–02/08
CFE
9