U2270B Datasheet, PDF (6/13 Pages) TEMIC Semiconductors – Read / Write Base Station IC

U2270B
Schmitt Trigger
The signal is processed by a Schmitt trigger to suppress
possible noise and to make the signal mC compatible. The
hysteresis level is 100 mV symmetrically to the dc opera-
tion point. The open-collector output is enabled by a low
level at OE (Pin 3).
7 mA
30 mA
OE
12602
Figure 11. Equivalent circuit of Pin OE
Driver (DRV)
The driver supplies the antenna coil with the appropriate
energy. The circuit consists of two independant 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 a 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 TEMIC
write method is described in the data sheets of TK5550
and TK5560. The various functions are controlled by the
inputs MS and CFE, refer to function table. The
equivalent circuit of the driver is shown in figure 4.
MS
12603
Figure 12. Equivalent circuit of Pin MS
30 mA
CFE
12604
Figure 13. Equivalent circuit of Pin CFE
6 (13)
TELEFUNKEN Semiconductors
Rev. A3, 13-Dec-96