Page 16
TPSi1085 User Guide
Rev 11/29
Technical Notes
Power Considerations
The maximum current for the +5V output is 17A. The maximum current for the +3.3V output is 8A. To
calculate the usable current given a speciic load, use the following formula:
Current
5V
]
●
[(Efficiency
3.3V
)(Power Conversion
5V/3.3V
)]
●
[(0.9)(1.5)]
Usable Current
3.3V
= [Output Current
MAX
Usable Current
3.3V
= (17 - 10)
Usable Current
3.3V
= 6.75A
For instance, given 10A on the 5V output, operating at 25°C (77°F)
with 0.9 eficiency on the 3.3V
output, the usable current for the 3.3V operation is as follows:
Temperature Deration (52°C to 85°C)
The TPSi1085 operates at an extended temperature, up to 85°C (185°F). If the ambient temperature
rises above 52°C (126°F), the TPSi1085 will experience temperature derating. To calculate the
maximum output current when the ambient temperature is within 52°C and 85°, simply locate the
ambient temperature and intersect of the appropriate slope using the graph below.
For instance, at 75°C the maximum 5V current with natural convection is 12.6A. This value would then
be used for the Output Current
MAX
in the above formula.
Ambient Temperature (°C)
Output Current (Amps)
Maximum Current Temperature Derating
with Baseplate
