MIC2590B-2BTQ Micrel Inc, MIC2590B-2BTQ Datasheet - Page 21

• Manufacturer Part Number: MIC2590B-2BTQ
• Description: IC PCI HOT PLUG CTLR DUAL 48TQFP
• Manufacturer: Micrel Inc
• Type: Hot-Swap Controllerr

Specifications of MIC2590B-2BTQ

• Applications: PCI, PCI-X
• Internal Switch(s): No
• Voltage - Supply: 3.3V, 5V, ±12V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 48-TQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Using this graph is not nearly as daunting as it may at
first appear. Taking the simplest case first, we’ll assume
that once a fault event such as the one in question
occurs, it will be along time, 10 minutes or more, before
the fault is isolated and the slot is reset. In such a case,
we can approximate this as a “single pulse” event, that is
to say, there’s no significant duty cycle. Then, reading up
from the X-axis at the point where “Square Wave Pulse
Duration” is equal to 0.1sec (=100ms), we see that the
effective thermal impedance of this MOSFET to a single
pulse event of this duration is only 6% of its continuous
R
This particular part is specified as having an R
50°C/W for intervals of 10 seconds or less. So, some
further math, just to get things ready for the finale:
Assume T
the drain leads, no airflow.
Assume the MOSFET has been carrying just about 5A
for some time.
Then the starting (steady-state)T
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 67°C:
R
At this point, the simplest thing to do is to approximate T
as 61°C, which will be close enough for all practical
purposes.
Micrel, Inc.
September 2008
θ(JA)
ON
at T
.
T
T
R
T
T
J
Fairchild Semiconductor
J
J
J
J
= 60.5°C =[1+(60.5°C–25°)(0.5%/°C)]×6.35mΩ
ON
International Rectifier
A
≅ 55°C + (7.3mΩ)(5A)
≅ 60.5°C
≅ 55°C + (7.3mΩ)(5A)
≅ 60.6°C
MOSFET Vendors
Resistor Vendors
Vishay (Siliconix)
= 55°C maximum, 1 square inch of copper at
at T
Vishay (Dale)
J
= 60.5°C ≅ 7.48mΩ
IRC
J
equal to the already calculated value
J
2
2
is:
(30°C/W)
(30°C/W)
Si4420DY (second source to Vishay)
FDS6670A (SO-8 package part)
IRF7413A (SO-8 package part)
FDS6644 (SO-8 package part)
FDS6688 (SO-8 package part)
Si4430DY (“LittleFoot” Series)
Si4420DY (“LittleFoot” Series)
(second source to “WSL”)
θ(JA)
Key MOSFET Type(s)
Sense Resistors
“OARS” Series
of
“WSL” Series
“LR” Series
J
21
Finally, add (10W)(67°C/W)(0.03) = 21°C to the steady-
state T
can easily handle this value of T
A second illustration of the use of the transient thermal
impedance curves: assume that the system will attempt
multiple retries on a slot showing a fault, with a one
second interval between retry attempts. This frequency
of restarts will significantly increase the dissipation in the
Si4430DY MOSFET. Will the MOSFET be able to handle
the increased dissipation? We get the following:
The same part is operating into a persistent fault, so it is
cycling in a square-wave fashion (no steady-state load)
with a duty cycle of (50msec/second = 0.05).
On the Transient Thermal Impedance Curves, read up
from the X-axis to the line showing Duty Cycle equaling
0.05. The effective R
Calculating the peak junction temperature:
And finally, checking the RMS power dissipation just to
be complete:
which will result in a negligible temperature rise.
The Si4430DY is electrically and thermally suitable for
this application.
MOSFET and Sense Resistor Selection Guide
Listed below, by Manufacturer and Type Number, are
some of the more popular MOSFET and resistor types
used in PCI hot plug applications. Although far from
comprehensive, this information will constitute a good
starting point for most designs.
J
T
P
to get T
J(PEAK MAX)
RMS
=
( ) (
5A
J(TRANSIENT MAX)
= [(10W)(4.7°C/W) + 55°C] = 102°C
2
www.vishay.com/docs/wsl_30100.pdf
θ(JA)
7.47mΩ
irctt.com/pdf_files/OARS.pdf
= (0.7 x 67°C/W) = 4.7°C/W.
irctt.com/pdf_files/LRC.pdf
www.fairchildsemi.com
www.siliconix.com
)
Web Address
Web Address
www.irf.com
J(MAX)
= 82°C. The Si4430DY
0.05
.
=
0.042W
M9999-091808
MIC2590B