U2270B Datasheet, PDF (3/13 Pages) TEMIC Semiconductors – Read / Write Base Station IC

Functional Description
Power Supply (PS)
DV_S
V_EXT
V_S
V _Batt
internal supply
U2270B
Standby
9V
25 kW
COILx
6V
6 V 18 V
PS
12 kW
DRV
DGND
11413
Figure 4. Equivalent circuit of power supply and antenna driver
The U2270 can be operated with one external supply
voltage or with two externally-stabilized supply voltages
for an extended driver output voltage or from the 12-V
battery voltage of a vehicle. The 12-V supply capability
is achieved via the on-chip power supply (see figure 4).
The power supply provides two different output voltages,
V_S and V_EXT.
V_S is the internal power supply voltage except for the
driver circuit. Pin V_S is used to connect a block capacitor.
V_S can be switched off by the pin STANDBY. In standby
mode, the chip’s power consumption is very low. V_EXT is
the supply voltage of the antenna’s pre-driver. This
voltage can also be used to operate external circuits, i.e.,
a microcontroller. In conjunction with an external NPN
transistor, it also establishes the supply voltage of the
antenna coil driver, DVS.
TELEFUNKEN Semiconductors
Rev. A3, 13-Dec-96
3 (13)