ATA5279-PLQW Atmel, ATA5279-PLQW Datasheet - Page 30

• Manufacturer Part Number: ATA5279-PLQW
• Description: RF Wireless Misc High-end multiple antenna driver IC
• Manufacturer: Atmel

Specifications of ATA5279-PLQW

• Package / Case: VQFN-48
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

30
Atmel ATA5279
T
Note:
Under worst case conditions, e.g., low supply voltage and high antenna impedance, the maxi-
mum antenna current might not be reached.
A “static” operation of ATA5279 is not allowed for typical transmit currents of several hundreds
of mAs. Typical applications are operated with a temporary LF field, resulting in an on/off oper-
ation mode of the chip. A suitable on/off duty cycle n
dissipation and keeps the thermal budget of the system. Therefore, following equation needs
to be fulfilled:
with
T
P
n
Note:
In addition to the average junction temperature T
a transmission must not be exceeded. The equation to be met is as follows:
with:
T
R
t
tau
n
Note:
T
1
amb
duty
duty
amb
peak
diss,tot
peak
thca
PCB
+
R
P
To define the operation limits, the static thermal resistance of the PCB must be known (see the
measurement hints in the application note). The Atmel
total thermal resistance of 42K/W.
It must be avoided to design the system's load profile in such a way that the protection features
of the chip are triggered under normal operating conditions. If the output voltage reaches the
upper shutdown limit, the power dissipation of the DC-DC converter increases significantly.
Consecutive triggering of the overtemperature shutdown may lead to a reduced lifetime.
Application Note “LF Antenna Driver ATA5279 – Thermal Considerations and PCB Design
Hints” available
thJA
diss
the application’s maximum ambient temperature
the total power dissipation of the chip
Operation duty cycle‚On-time during period, t
maximum peak temperature = 200°C
Thermal resistance case-to-ambient (PCB)
Transmission on-time, 10 ms t
Thermal time constant of PCB (R
Operation duty cycle
P
R
diss,tot
thjc
+
R
thca
n
duty
T
1 e
j,max
–
------------- -
PCB
t
1
+
n
1
duty
thca
1 sec
j,max
, the maximum peak temperature during
C
P
thca
diss
®
)
ATAB5279 application board features a
duty
1
/t
per
R
reduces the average power
thjc
+
R
thca
+
T
amb
9125L–RKE–03/11