MIC2004 Micrel, MIC2004 Datasheet - Page 15

• Manufacturer Part Number: MIC2004
• Description: Fixed Current Limit Power Distribution Switch
• Manufacturer: Micrel

August 2005
Micrel
In normal operation MIC2004/2014’s Ron is low enough
that no significant I
most often caused by a short circuit, or very heavy load,
when a significant portion of the input supply voltage
appears across MIC2004/2014’s power MOSFET.
Under these conditions the heat generated will exceed
the package and PCB’s ability to cool the device and
thermal limiting will be invoked.
In Figure 10 die temperature is plotted against I
assuming a constant case temperature of 85°C. The
plots also assume a worst case R
temperature of 135°C. Under these conditions it is clear
that an SOT-23 packaged device will be on the verge of
thermal shutdown, typically 145°C die temperature,
when operating at a load current of 1.25A. For this
reason
MIC2004/2014s for any design intending to supply
continuous currents of 1A or more.
T
R
A
θ (J-A)
= ambient temperature
160
140
120
100
80
60
40
20
0
we
is the thermal resistance of the package
0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00
Die Temperature vs. Iout for Tcase = 85°C
recommend
2
R heating occurs. Device heating is
Iout - Amps
using
ON
of 140 mΩ at a die
MLF
SOT-23
MLF
packaged
OUT
15
Figure 10 assumes no backside contact is made to the
thermal pad provided on the MLF package. For optimal
performance at higher current levels, or in higher
temperature environments, thermal contact with the
PCB and the exposed power paddle on the back side of
the MLF package should be made. This significantly
reduces the package’s thermal resistance and thus
extends the MIC2004/2014’s operating range. It should
be noted that this backside paddle is electrically active
and is connected to MIC2004/2014’s GND pin.
to Ground Plane
Figure 11. Pad for thermal mounting to PCB
0.3 mm diam.
2 Vias
Figure 10. Die Temperature vs. I
0.8 mm
MIC2004/MIC2014
www.DataSheet4U.com
1.4 mm
OUT
[phone]
M9999-080305