ATA5278 ATMEL Corporation, ATA5278 Datasheet - Page 19

• Manufacturer Part Number: ATA5278
• Description: Stand-alone Antenna Driver
• Manufacturer: ATMEL Corporation

3.15
4832D–RKE–12/07
Current Adjustment
I
The maximum reachable output current in the antenna circuit can be calculated as follows:
Here, V
the R
calculating the amount of complex Z, that the antenna driver output frequency (i.e., f = f
has to be taken into account for the complex parts of the impedance.
The antenna coil current can be adjusted in 16 steps by modifying the IC0..IC3 bits in the config-
uration register 1. Dependent on the selected current, the duty cycle of the antenna coil driver
signal is adapted. This improves the possibility to use one and the same antenna over the whole
range of selectable output currents.
steps.
Table 3-3.
ant,eff
Note:
Step
16
DSon
10
11
12
13
14
15
1
2
3
4
5
6
7
8
9
=
(1)
DRV
V
---------------------------- - A
1. Default
of the QSC MOSFET, the shunt resistor and the driver output resistance). Note when
DRV
is the maximum reachable driver voltage and Z the antenna’s impedance (including
Current Settings
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
maximum
maximum
maximum
maximum
maximum
maximum
maximum
maximum
maximum
maximum
maximum
maximum
maximum
maximum
maximum
maximum
Z
Current [mA]
2
/3.597
/3.226
/2.976
/2.604
/2.353
/2.132
/1.984
/1.825
/1.709
/1.57
/1.456
/1.361
/1.256
/1.163
/1.081
IC0
Table 3-3
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
provides a list of the current settings for all 16
IC1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
IC2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
IC3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
ATA5278
1.750/6.25
1.25/6.75
1.25/6.75
1.25/6.75
1.25/6.75
1.75/6.25
1.75/6.25
1.75/6.25
P/P ratio
2.5/5.5
2.5/5.5
2.5/5.5
2.5/5.5
4/4
4/4
4/4
4/4
OSC
/64)
19