Environmental specifications, Thermal considerations – ThingMagic Micro Hardware User Manual
Page 29
Environmental Specifications
A D I V I S I O N O F T R I M B L E
Hardware Overview
29
Environmental Specifications
Thermal Considerations
There are two ways of mounting the Micro, see
details. One is to solder the board to the motherboard using its side “vias”, with the RF
shield can facing upward. The other is to use the board-to-board connectors to connect to
the motherboard and solder the 4 tabs on the shield to the motherboard as well. The
orientation with the side “vias” soldered down is best for wicking heat away from the
module.
Most applications involve the module transmitting periodically to inventory tags in the
field. The longer the transmitter is on in relation to its off time (the “duty cycle”) the faster
the temperature will rise. The module will not transmit if the temperature is at a dangerous
level, but will transmit again as soon as the temperature drops – often so quickly it is
hardly noticeable. Other factors that affect the time before the module begins to protect
itself is the ambient temperature and the power level at which the module is transmitting.
These factors are represented in the following table, which give the typical minutes of
transmission time before thermal protection is enabled:
Thermal Calculations
Mounting
Ambient
Temp (°C)
RF Power
(dBm)
Duty Cycle
%
Time (m) to reach
max temperature
Soldered down
-40
30
98
No restriction
Soldered down
25
23
98
No restriction
Soldered down
25
30
80
No restriction
Soldered down
25
30
90
7.34
Soldered down
25
30
98
5.99
Soldered down
60
23
50
No restriction
Soldered down
60
23
60
7.59
Soldered down
60
23
80
2.24
Soldered down
60
23
98
1.46
Soldered down
60
30
30
No restriction
Soldered down
60
30
50
4.17