ata5277-pcq ATMEL Corporation, ata5277-pcq Datasheet - Page 11

• Manufacturer Part Number: ata5277-pcq
• Description: Stand-alone Antenna Driver
• Manufacturer: ATMEL Corporation

Modulation
QSC Feature
4669B–RKE–10/03
After the IC has woken up and a command has been received, the DIO line is used for
LF modulation. The IC has two modulation modes, ASK and PSK. The mode can be
selected with the control command '0', bit 2. If ASK modulation mode is selected
(NASK_PSK = 0), the IC switches the carrier on and off, depending on the state of the
DIO line ('1' is on, '0' is off). Note that, depending on the quality of the connected LF
antenna and on the desired LF data rate, the usage of the QSC transistor T1 (see typi-
cal applications section) is neccessary. If PSK mode is selected (NASK_PSK = 1), the
phase of the carrier is shifted by 180° on any change of the DIO line. Here, the QSC
transistor must be used.
Figure 9. Modulation Modes
The IC switches from modulation mode to command mode if the DIO-line has not been
changed for a time peraiod longer than t
The Quick Start Control (QSC) feature supports a short oscillation build up and decay
timing during LF data modulation. An external high-voltage MOS transistor is used as a
switch to close and open the current loop of the antenna. By synchronizing this switch to
the zero-crossing events of the antenna current, very short build-up and decay times for
the LF-field and hence high data baud rates can be achieved.
Figure 10. QSC Operation
The external transistor (T1 in the typical applications section) is driven by the QSC pin. It
provides a fast and synchronized gate-driver signal.
Coil Voltage
(PSK Mode)
Coil Voltage
(ASK Mode)
D_IO
DIO
QSC
Coil
with QSC transistor
ASK Modulation
Modulation after Setup
modsel
ATA5277 [Preliminary]
.
PSK Modulation
Switch Off
Cycle
Standby
11