Texas Instruments TPS73501EVM-276 Evaluation Module TPS73501EVM-276 TPS73501EVM-276 Datenbogen
Produktcode
TPS73501EVM-276
5
Board Layout
5.1
Layout
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Board Layout
The thermal resistance from junction to ambient for the TPS735xxEVM has a typically value of 27.5
°
C/W.
The recommended maximum operating junction temperature specified in the data sheet for the TPS735xx
family is 125
family is 125
°
C. With these two pieces of information, the maximum power dissipation can be found by
using
Example Calculation:
For example, what is the maximum input voltage that can be applied to a TPS73525 (fixed 2.5-V output) if
the ambient temperature is 85
the ambient temperature is 85
°
C and the full 500 mA of load current is required?
Given: T
J
= 125
°
C, T
A
= 85
°
C,
θ
JA
= 27.5
°
C/W
(2)
Using
, substitute in the preceding given values and find that the maximum power dissipation
for the part is P
d
= 1.45 W.
125
°
C = 85
°
C + P
d
(27.5
°
C/W)
(3)
This means that the total power dissipation of the TPS73525 must be less than 1.45 W. Now, the input
voltage can be calculated.
voltage can be calculated.
P
d
= (V
in
– V
out
)
×
I
out
= (Vin – 2.5V)
×
0.5 A = 1.45 W
(4)
So, the maximum input voltage needs to be 5.4 V or less in order to maintain a safe junction temperature.
Similar analysis can be performed to determine the maximum ambient temperature over a range of
operation. The maximum recommended input voltage for the TPS735xx is 6.5 V. You can calculate the
highest ambient temperature allowed and still provide full output current. The answer depends on the
output voltage.
operation. The maximum recommended input voltage for the TPS735xx is 6.5 V. You can calculate the
highest ambient temperature allowed and still provide full output current. The answer depends on the
output voltage.
Output Voltage (V)
Maximum Ambient Temperature
°
C
1.8
60.3
2.5
70
3.3
81
This section provides the TPS735xxEVM-276 board layout and illustrations
When laying out the board for the TPS735xx, TI recommends that the board be designed with separate
ground planes for Vin and Vout which are only connected at the GND pin of the device. Also, the ground
connection for the bypass capacitor must be connected directly to the GND pin of the device. By following
the foregoing two guidelines, you can improve the PSRR performance of the TPS735xx. See the
TPS735xx data sheet (
ground planes for Vin and Vout which are only connected at the GND pin of the device. Also, the ground
connection for the bypass capacitor must be connected directly to the GND pin of the device. By following
the foregoing two guidelines, you can improve the PSRR performance of the TPS735xx. See the
TPS735xx data sheet (
) for specific layout guidelines.
SLVU256A – August 2008 – Revised November 2008
TPS735xxEVM-276
3