MAS9124 데이터 시트보기 (PDF) - Micro Analog Systems Oy
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MAS9124 Datasheet PDF : 14 Pages
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APPLICATION INFORMATION
Auto-Discharge Function
MAS9124 has a shutdown transistor that turns on,
when the device is disabled, and discharges the
output capacitor.
Calculating Maximum Power Dissipation
Maximum power dissipation of the package may
limit output current or input voltage, which can be
used, especially with the combination of low output
voltage and high input voltage.
The power dissipation can be calculated by using
the formula:
Pd = (VIN− VOUT ) * IOUT + VIN * IGND
It shall not exceed the maximum power dissipation,
allowed by the package:
PdMAX
=
TJMAX − TA
RJA
where TJMAX is maximum junction temperature
(TJMAX = 125°C), TA is ambient temperature and RJA
is junction-to-ambient thermal resistance of the
package.
DA9124.009
11 January 2005
When assumed that:
TA = +55°C, VOUT = 1.5 V, VIN = 5.0 V and used
package is SOT23-5 the equation yields:
PdMAX
= 125°C − 55°C
191°C/W
= 0.366 W
from which can be calculated:
IOUTMAX
=
PdMAX
VIN − VOUT
= 105 mA
VIN * IGND is negligible and can be omitted.
Consequently, it can be seen that under these
conditions the average output current should not
exceed 105 mA.
7 (14)
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