MIC2582-MYM Micrel Inc, MIC2582-MYM Datasheet - Page 21

• Manufacturer Part Number: MIC2582-MYM
• Description: Single-Channel Hot-Swap Controller - 100mV Fast-Trip Threshold -
• Manufacturer: Micrel Inc
• Type: Hot-Swap Controllerr

Specifications of MIC2582-MYM

• Applications: General Purpose
• Internal Switch(s): No
• Voltage - Supply: 2.3 V ~ 13.2 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Thus:
Assume T
the drain leads, no airflow.
Recalling from our previous approximation hint, the part
has an R
Assume it has been carrying just about 2.5A for some
time.
When performing this calculation, be sure to use the
highest anticipated ambient temperature (T
which the MOSFET will be operating as the starting
temperature, and find the operating junction temperature
increase (∆T
final junction temperature is found by adding T
∆T
close approximation may take one or two iterations, and
the calculation tends to converge quickly.
Then the starting (steady-state) T
Micrel, Inc.
April 2009
J
. Since this is not a closed-form equation, getting a
T
T
J
J
≅ T
≅ T
≅ 55ºC + [17mΩ + (55ºC-25ºC)(0.005)(17mΩ)]
ON
A(MAX)
A(MAX)
A
= 55°C maximum, 1 square inch of copper at
of (0.0335/2) = 17mΩ at 25°C.
J
) from that point. Then, as shown next, the
+ [R
+ ∆T
x I
2
ON
x R
J
+ T
θ(JA)
A(MAX)
– T
J
A
is:
)(0.005/ºC)(R
Figure 10. Transient Thermal Impedance
A(MAX)
A(MAX)
ON
)]
) in
and
21
Iterate the calculation once to see if this value is within a
few percent of the expected final value. For this iteration
we will start with T
of 61.1°C:
So our original approximation of 61.1ºC was very close
to the correct value. We will use T
Finally, add the temperature increase due to the
maximum power dissipation calculated from a “single
event”, (11.25W)(50ºC/W)(0.08) = 45ºC to the steady-
state T
acceptable maximum junction temperature for this part.
T
T
T
J
J
J
≅ (55ºC + (0.122W)(50ºC/W)
≅ T
 ≅ (55ºC + (0.125W)(50ºC/W)  ≅ 61.27ºC
≅ 61.1ºC
J
to get T
A
+ [17mΩ + (61.1ºC-25ºC)(0.005)(17mΩ)]
x (2.5A)
x (2.5A)
J
J(TRANSIENT MAX.)
equal to the already calculated value
2
x (50ºC/W)
2
x (50ºC/W)
J
= 106ºC. This is an
= 61ºC.
MIC2582/MIC2583
M9999-043009-C