MIC61300 Datasheet, PDF (14/22 Pages) Micrel Semiconductor – Low Input Voltage, Single-Supply High-Current LDO

Micrel, Inc.
To determine the maximum power dissipation allowed
that would not exceed the IC’s maximum junction
temperature (125°C) when operating at a maximum
ambient temperature of 75°C by:
P_D(MAX) = (T_J(MAX) – T_A) / θ_JA
= (125°C − 75°C) / (60.7°C/W)
= 0.824W
Eq. 6
Thermal Measurements
It is always wise to measure the IC’s case temperature
to make sure that it is within its operating limits. Although
this might seem like a very elementary task, it is very
easy to get erroneous results. The most common
mistake is to use the standard thermal couple that
comes with the thermal voltage meter. This thermal
couple wire gauge is large, typically 22 gauge, and
behaves like a heatsink, resulting in a lower case
measurement.
There are two suggested methods for measuring the IC
case temperature: a thermal couple or an infrared
thermometer. If a thermal couple is used, it must be
constructed of 36 gauge wire or higher to minimize the
wire heatsinking effect. In addition, the thermal couple tip
must be covered in either thermal grease or thermal glue
to make sure that the thermal couple junction is making
good contact to the case of the IC. This thermal couple
from Omega (5SC-TT-K-36-36) is adequate for most
applications.
MIC61300
To avoid this messy thermal couple grease or glue, an
infrared thermometer is recommended. Most infrared
thermometers’ spot size are too large for an accurate
reading on small form factor ICs. However, an IR
thermometer from Optris has a 1mm spot size, which
makes it ideal for the 3mm × 3mm MLF^® package. Also,
get the optional stand. The stand makes it easy to hold
the beam on the IC for long periods of time.
Enable
The MIC61300 features an active high enable input (EN)
that allows ON/OFF control of the regulator. The current
through the device reduces to near “zero” when the
device is shutdown, with only microamperes of leakage
current. The EN input may be directly tied to V_IN or
driven by a voltage that is higher than V_IN as long as the
voltage does not exceed the maximum operating rating
of the EN pin.
September 2010
14
M9999-092910-A