MIC2005-0.5YM6TR Ver la hoja de datos (PDF) - Micrel
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MIC2005-0.5YM6TR Datasheet PDF : 25 Pages
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Micrel, Inc.
MIC20XX Family
Functional Description
VIN and VOUT
VIN is both the power supply connection for the internal
circuitry driving the switch and the input (Source
connection) of the power MOSFET switch. VOUT is the
Drain connection of the power MOSFET and supplies
power to the load. In a typical circuit, current flows from
VIN to VOUT toward the load. Since the switch is bi-
directional when enabled, if VOUT is greater than VIN,
current will flow from VOUT to VIN.
When the switch is disabled, current will not flow to the
load, except for a small unavoidable leakage current of
a few microamps. However, should VOUT exceed VIN by
more than a diode drop (~0.6 V), while the switch is
disabled, current will flow from output to input via the
power MOSFET’s body diode.
If discharging CLOAD is required by your application,
consider using MIC20X4 or MIC20X7; these MIC20XX
family members are equipped with a discharge FET to
insure complete discharge of CLOAD.
Current Sensing and Limiting
MIC20XX protects the system power supply and load
from damage by continuously monitoring current
through the on-chip power MOSFET. Load current is
monitored by means of a current mirror in parallel with
the power MOSFET switch. Current limiting is invoked
when the load exceeds the set over-current threshold.
When current limiting is activated the output current is
constrained to the limit value, and remains at this level
until either the load/fault is removed, the load’s current
requirement drops below the limiting value, or the switch
goes into thermal shutdown.
Kickstart
2003 2004
2013 2014
2005
2015
2006
2016
2007
2017
2008
2018
2009
2019
Only parts in white boxes have Kickstart.
(Not available in 5-pin SOT-23 packages)
The MIC201X is designed to allow momentary current
surges (Kickstart) before the onset of current limiting,
which permits dynamic loads, such as small disk drives
or portable printers to draw the energy needed to
overcome inertial loads without sacrificing system
safety. In this respect, the Kickstart parts (MIC201X)
differs markedly from the non-Kickstart parts (MIC200X)
which immediately limit load current, potentially starving
the motor and causing the appliance to stall or stutter.
During this delay period, typically 128ms, a secondary
current limit is in effect. If the load demands a current in
excess the secondary limit, MIC201X acts immediately
to restrict output current to the secondary limit for the
duration of the Kickstart period. After this time the
MIC201X reverts to its normal current limit. An example
of Kickstart operation is shown below.
Figure 3. Kickstart Operation
Figure 3 Label Key:
A) MIC201X is enabled into an excessive load (slew
rate limiting not visible at this time scale) The initial
current surge is limited by either the overall circuit
resistance and power supply compliance, or the
secondary current limit, whichever is less.
B) RON of the power FET increases due to internal
heating (effect exaggerated for emphasis).
C) Kickstart period.
D) Current limiting initiated. FAULT/ goes LOW.
E) VOUT is non-zero (load is heavy, but not a dead short
where VOUT = 0V. Limiting response will be the
same for dead shorts).
F) Thermal shutdown followed by thermal cycling.
G) Excessive load released, normal load remains.
MIC201X drops out of current limiting.
H) FAULT/ delay period followed by FAULT/ going
HIGH.
Under Voltage Lock Out
Under voltage lock-out insures no anomalous operation
occurs before the device’s minimum input voltage of
UVLOTHRESHOLD which is 2V minimum, 2.25V typical, and
2.5V maximum had been achieved. Prior to reaching
this voltage, the output switch (power MOSFET) is OFF
and no circuit functions, such as FAULT/ or ENABLE,
are considered to be valid or operative.
January 2009
17
M9999-012109-A
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