ata5279n ATMEL Corporation, ata5279n Datasheet - Page 8

• Manufacturer Part Number: ata5279n
• Description: Antenna Driver For Multiple Antennas
• Manufacturer: ATMEL Corporation

3.5
3.6
8
Coil Current Sensing (Zero Cross, Sample and Hold, Integrator)
Diagnosis
ATA5279N [Preliminary]
The coil current flows through an external shunt resistor, causing a current-dependant voltage,
which is fed into the IC via the VSHS pin. By monitoring the zero crossing events of this signal,
the phase of the coil current is known and hence the positive peak value can be sampled.
The peak coil current is then subtracted from an internal reference voltage that is dependant on
the selected coil current, which results in the regulation difference.
An amplifier stage converts this difference into a current, which is then fed into an externally
applied integration capacitor connected to the CINT pin. The resulting voltage on this capacitor
directly influences the amplitude of the sine wave signal. It also determines the supply voltage
generated by the boost converter, if the necessary coil supply voltage exceeds the actual supply
voltage level. Note that during an active transmission, this voltage is internally limited to
V
Note that in idle mode, the voltage on the integration capacitor is kept at a value that corre-
sponds to the battery supply voltage. This ensures that the boost converter, if needed, always
performs a soft start from the battery voltage level on.
The desired current can be selected via the SPI. A total of 20 predefined steps are available,
divided into the following sections:
The IC allows the use of a current step not intended for a particular driver group; however, in this
case, full functionality, especially a stabilized coil current, cannot be guaranteed. See also the
Control Logic block description for an overview over the commands.
The diagnosis stage monitors both the positive (AxP) and negative (AxN) connection lines of the
six coils. If one of these lines is shorted to battery supply or to ground, the following measures
are taken for protection and diagnostic reasons:
In addition to short circuits, a disconnected coil (i.e., open load) or an excessive junction temper-
ature can also lead to such a fault shutdown.
Note that this type of diagnosis is carried out continuously during normal operation of the IC to
protect both the IC and the peripherals from damage.
In the event of such a fault shutdown, the IC can be brought back to operation by resetting its
fault register with the appropriate SPI command (please refer also to the
Command Description” on page 20
faulty coils is still possible even if there is a failure of one coil.
CINT,max
• The lower four steps (50 mA to 200 mA) are intended for the low-current coils only
• The next ten steps (250 mA to 700 mA) are intended for both types of coils
• The upper six steps (750 mA to 1A) are intended only for the high-current coils
• All coil driver stages are shut down, i.e., put into high impedance state
• The shunt resistor is disconnected from the coil return lines
• The reason for the fault shutdown is stored in the fault register
• An interrupt request is triggered (see also control logic block)
.
later in this document). As a result, transmission on non-
Section 3.9.2 “General
9125C–RKE–01/09