ata5277-pcq ATMEL Corporation, ata5277-pcq Datasheet - Page 13

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

Fault Diagnotics
4669B–RKE–10/03
The maximum output current can be selected with the external shunt resistor. Its resis-
tance can be calculated with the formula:
where the minimum and maximum ratings for I
tics have to be considered. See Figure 11 to determine the antenna´s parameters.
The maximum reachable output current can be calculated as follows:
Here, V
ance (inculding the R
resistance).
The IC contains several fault diagnotic stages to protect itself from destruction and to
provide diagnostic information. Once there is a fault detected, both the switch mode
power supply and the antenna driver stage are switched off and the corresponding fault
information is written into the status register. Note that besides shutting down the driver
stages, the ATA5277 will not change its behaviour (i.e., it will remain in modulation
mode until the DIO line timeout has occured). The fault information can be read out from
status command 4, which will also reset the status register.
Following protection and diagnostic mechanisms are defined:
•
•
The diagnostic bits contain the information as given in Table 10 on page 14.
R
I
ant,peak
shunt
General
–
DRV output
–
–
=
DRV
The IC is equipped with temperature measurement obilities in order to detect
a critical junction temperature
Short-circuit protection of the driver stage output is realized by means of
voltage monitoring. Thus, the output voltage is compared to a corresponding
threshold (depeding on the active transistor in the power MOS half-bridge). If
this threshold is surpassed for several oscillations, a Short Circuit (SC) fault
is detected;
Open load or QSC transistor SC to GND is detected with the external current
sensing resistor R
active, there is at least one of those two faults present. There is no possibility
to determine the exact fault source.
=
--------------------- - W
I
max,peak
V
----------------------- - A
is the maximum reachable driver voltage (40 V) and Z the antenna´s imped-
p
DRV
1
´
Z
´
2
DSon
of the QSC MOSFET, the shunt resistor and the driver output
Shunt
. If there is no signal at this point even if the output is
ATA5277 [Preliminary]
maximum,peak
quoted in the DC characteris-
13