ata5279n ATMEL Corporation, ata5279n Datasheet - Page 6

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

3.3
6
Sine Wave Generator
ATA5279N [Preliminary]
The sinusoidal coil-driving signal is internally generated. Its amplitude is dependant on the mea-
sured coil current, and the frequency is derived from the oscillator stage. In conjunction with the
output driver stages, the generated signal is optimized for low harmonic distortions.
The peak-to-peak amplitude of the sinusoidal signal is directly defined by the voltage on the
external integration capacitor connected to the CINT pin. This voltage, with an offset subtracted,
is internally used to generate a low-voltage sine wave signal, which is in turn amplified and
level-shifted up to the desired output level.
The output signal itself has a DC offset close to the half of the supply voltage, and the maximum
possible amplitude has about 3V distance to each of the supplies.
Figure 3-2.
In application, the output coil current is the fixed valued (selectable via SPI). Hence, the required
output voltage is calculated as follows:
Here, Z
priate return line current selector (see also
R
Section 4. “Application” on page
V
Out,p
Shunt
=
is the resistance of the externally applied current sense shunt resistor (typ. 1 , see also
Coil
I
Coil,p
is the complex impedance of the coil, R
Maximum Possible Coil Driving Signal for a Given Supply Voltage VDS
0.5
V
V
Z
OUT,max
OUT,min
Coil
GND
VDS
VDS
+
R
DSon,HRS/LRS
26).
+
R
Shunt
Section 6. “Functional Parameters” on page
DSon,HRS/LRS
is the on-resistance of the appro-
Figure 3-2
illustrates this.
9125C–RKE–01/09
28) and