CHAPTER 3
49
Application
3.1
Passive Entry Function
The standard application of 3D-AFE is the Passive (Keyless) Entry function. The car driver
approaches the car and triggers the Base Station by pulling the door handle or by another trig-
ger mechanism. The Base Station transmits the Passive Entry (PE) Wake Pattern, a Command
and a Challenge using typically an outdoor Antenna, for example in the outside mirror. The
Antenna is driven by a LF Transceiver, which is typically activated with an active low signal
called TXCT- (see Figure 28).
It is assumed that the Identification Device is in Standby Mode (WDEEN=high). During
Wake-up Time the IC internal wake (WAKEI) will be activated if the threshold VWAKEA
is exceeded at one or more antennas. The first WAKEI signal determines the receive channel.
During the Waiting Time the Base Station will start modulation while sending the Passive En-
try Wake Pattern. The internal clock CLKI will be active during this period.
If the received PE Wake Pattern is equal to the PE Wake Pattern in the EEPROM, the RF level
check with VWAKEB will NOT be performed and the 3D-AFE will activate the output
WAKE at once. This will cause the Microcomputer of the Identification Device to wake-up
after an eventually µC Wake Delay. Depending on the required time the Base Station should
insert an active period between Wake Pattern and Command transmission. The digitized am-
plitude modulation is output at the EOBA and demodulation is done by the Microcomputer.
For this purpose the CLKA signal can be used as reference, which is available at output
EOBA/M.
The Command sent to the Microcomputer must include an information that a Passive Entry
action is requested.
