MC33690 Datasheet, PDF (13/24 Pages) Motorola, Inc – Standalone Tag Reader Circuit

Freescale S^Me^Cm³³i⁶c⁹o⁰nductor, Inc.
DIRECT CONNECTION TO A MICROCONTROLLER CONFIGURATION
When a high level is applied on MODE1, the
circuit is in configuration C (direct connection to
a microcontroller configuration, see figure 15
page 19).
regulator. The driver outputs TD1 and TD2 are
frozen in their state (high or low level) before
entering into standby mode. DOUT forces a low
level.
The demodulated data are sent through DOUT.
The AM pin is set as a VDD referenced input pin
receiving the AM command. Forcing high and
low levels on AM achieves the amplitude
modulation by switching on/off both antenna
drivers. Meanwhile, this amplitude modulation
can be monitored on DOUT. This allows antenna
short and open circuit diagnosis.
The circuit can be put into standby mode by
applying a low level on the MODE2 pin.
In standby mode, the oscillator and most of the
internal biasing currents are switched off.
Therefore, the functions (tag reader, ISO 9141
interface) are inactive except the voltage
The ISO 9141 interface K is standalone and can
be directly controlled by the input pin Tx and
monitored by the output Rx.
Applying a logic high level on Tx switches the
output driver K on (dominant zero state when an
external pull-up resistor is connected between K
and VBAT). Applying a logic low level turns the
driver off (one recessive state).
Rx monitors the voltage at the K pin. When the
voltage is below the low threshold voltage, Rx
forces a logic low level. When the voltage is
above the high threshold voltage, Rx forces a
logic high level.
In standby mode, Tx is disabled and Rx output
monitors the voltage at the K pin.
Figure 10 : Configuration C state diagram
reset
TD1/2
switching
AM low
AM high
wake up
AM high
AM low
TD1/2 off
mode2 low
mode2 high
standby
mode2 low
© Motorola, Inc., 2002.
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revision 4.8, 5 February 2002