MaximumSafeAmbientCurrent.py Python Code

FQP27P06 abbreviated Specifications

Max. Operating Temperature: 175 ℃, Thermal Resistance: 62.5 ℃ / W, Drain to Source ON Resistance: 0.07 Ω

"""
Calculate safe Current over Ambient [25 degree C] of Transistor [MOSFET].

Based on sparkfun electronics 'P-Channel MOSFET 60V 27A' Comment post by 'Jay2'.

Jay2 Posted:

Hey guys! Do remember the basic thermals!
This will heat at 62.5 degree C per watts un ambiant.

This guy have a 0.070 Ohm RDSon.

The maximum temp is 175dC.

Hence:

175-25=150dC of margin for heat.

150/62.5 = 2.4W maximal

P = R(I*I), so: 2.4/0.07 = I*I.

I = 5.855Amp.
So remember: This will pass no more than a safe 5A over ambiant. Anything above that will require serious heat-sinking.
"""

# --------------------------------------------------------------------------------------------------------------------- #
# Library Imports

# Allows Python 2.x to use Python 3.x 'print()' Function correctly. This Line must be before all other 'import' Entries.
from __future__ import print_function

# 'import' UNIX 'os' Library, and use 'os.system' to call 'clear' command.
import os;
os.system('clear');

# 'import' 'math' Library, to access Trigonometric functions.
import math;

# --------------------------------------------------------------------------------------------------------------------- #
# Code starts here.

print ("Calculate maximum Current at Ambient with no Heatsink")
print ("");

maximumOperatingTemperature = float(raw_input ("Enter Maximum Operating Temperature: "));
ambientCperWatts = float(raw_input ("Enter Thermal Resistance: "));
turnOnResistance = float(raw_input ("Enter Drain to Source ON Resistance: "));

marginOfHeat = maximumOperatingTemperature - 25
maximalWatts = marginOfHeat / ambientCperWatts
maximumAmbientCurrent = math.sqrt(maximalWatts / turnOnResistance)

# Display the calculated Values.
print ("");
print (" ---------- ---------- ----------- ---------- ---------- ");
print ("Entered:");
print (" Maximum Operating Temp. : ", maximumOperatingTemperature, "degree C");
print (" Thermal Resistance: ", ambientCperWatts, "degree C / Watt");
print ("Drain to Source ON Resistance: ", turnOnResistance, "Ohms");
print ("");
print (" ---------- ---------- ----------- ---------- ---------- ");
print ("Calculated:");
print (" Maximum Safe Current w/o Heatsink: ", round(maximumAmbientCurrent,3), "Amperes");
print ("");

# Code ends here.
# --------------------------------------------------------------------------------------------------------------------- #

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