ATA5278-PKQI Atmel, ATA5278-PKQI Datasheet - Page 17

IC ANTENNA DVR STAND-ALONE 28QFN

ATA5278-PKQI

Manufacturer Part Number
ATA5278-PKQI
Description
IC ANTENNA DVR STAND-ALONE 28QFN
Manufacturer
Atmel
Type
Stand Alone Antenna Driverr
Datasheet

Specifications of ATA5278-PKQI

Rf Type
TPM
Frequency
125kHz
Package / Case
28-VFQFN
Maximum Operating Temperature
+ 105 C
Mounting Style
SMD/SMT
Minimum Operating Temperature
- 40 C
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Features
-
Lead Free Status / Rohs Status
Lead free / RoHS Compliant
Other names
ATA5278-PKQITR
3.13
Figure 3-13. Antenna Current Regulation Loop
4832D–RKE–12/07
Current Regulation
Selected
current
+
The antenna driver stage and the boost converter are thermally monitored in order to protect
them from overheating, and the output pin DRV1 is short-circuit protected by means of current
limitation. For further details, please refer to the section
The current sensor system is equipped with a zero-crossing detector and a sample and hold
stage. The zero-crossing detector provides the synchronization signal for the driver control logic,
which then calculates the phase shift between the antenna driver output signal and the current
flowing through the antenna. Based on this phase information, the sample and hold stage is con-
trolled in order to sample the top point of the input signal, hence the peak current value.
A main feature of the ATA5278 is its ability to generate a stabilized magnetic field with a con-
nected LC antenna, mainly independent of the battery voltage and the frequency mismatch
between the driver output frequency and the antenna resonance frequency.
The input signal for the regulation loop in
defined in configuration register 1. An external shunt resistor of 1 , which has to be connected
to the VSHUNT pin, is used to measure the current in the LC antenna. As the peak voltage over
this resistor is directly linked with the peak current in the antenna and hence the magnetic field
strength, this value can be seen as output. This signal is sampled and held by an internal stage
controlled by the control logic. The difference of the input signal and the sampled signal then
controls an integrator. The parameter of this stage can be influenced with an externally applied
charging capacitor connected to the CINT pin. The charging/discharging behavior of the integra-
tor stage is described in
-
Integrator
CINT
Figure 3-14 on page
converter
VBATT
control
Boost
Current
sample
VDS
hold
and
Figure 3-13
DMOS half
bridge
18.
DRV1
is the selected antenna current, which is
“Fault Diagnosis” on page
LC antenna
VSHUNT
ATA5278
20.
17

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