MP5000A – 12V, 1A-5A PROGRAMMABLE CURRENT LIMIT SWITCH
MP5000A Rev. 1.01 www.MonolithicPower.com 10
10/16/2014 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2014 MPS. All Rights Reserved.
OPERATION
The MP5000A is designed to limit the in-rush
current to the load. It offers an integrated solution
to monitor the input voltage, output voltage,
output current and die temperature.
Under Voltage Lock Out Operation
If the supply (input) is below the UVLO threshold,
the output is disabled, and the fault line is driven
low.
When the supply goes above the UVLO
threshold, the output is enabled and the fault line
is released. When the fault line is released it will
be pulled high by a 28uA current source. No
external pull up resistor is required. In addition,
the pull up voltage is limited to 5 volts.
Output Over Voltage Protection
If the input voltage is higher than the OVP
threshold, the output will be clamped at 15V
(typical).
Current Limit
When the part is active, if load reaches trip
current (minimum threshold current triggering
over current protection) or a short is present, the
part switches into to a constant-current (hold
current) mode. Part will be shutdown only if the
over current condition stays long enough to
trigger thermal protection.
However, when the part is powered up by V
CC
or
EN, the load current should be smaller than hold
current. Otherwise, the part can’t be fully turned
on.
In a typical application using a current limit
resistor of 22, the trip current will be 4.7A and
the hold current will be 3.6A. If the device is in its
normal operating state and passing 2.0A it will
need to dissipate only 160mw with the very low
on resistance of 40m. For the package
dissipation of 50°C/Watt, the temperature rise will
only be + 8°C. Combined with a 25°C ambient,
this is only 33°C total package temperature.
During a short circuit condition, the device now
has 12V across it and the hold current clamps at
3.6A and therefore must dissipate 43W. At
50°C/watt, if uncontrolled, the temperature would
rise above the MP5000A thermal protection
(+175°C) and shutdown the device to cause the
temperature to drop below a hysteresis level.
Proper heat sink must be used if the device is
intended to supply the hold current and not
shutdown. Without a heat sink, hold current
should be maintained below 250mA at + 25°C
and below 150mA at +85°C to prevent the device
from activating the thermal shutdown feature.
Thermal protection
When thermal protection is triggered, the output
is disabled and the fault line is driven to the
middle level. The thermal fault condition is
latched, and the part will remain latch off state
until restart the power or reset the enable pin.
Enable / Fault Pin
The Enable/Fault Pin is a Bi-Directional three
levels I/O with a weak pull up current (28uA
typical). The three levels are low, mid and high. It
functions to enable/disable the part and to relay
Fault information.
Enable/Fault pin as an input:
1. Low and mid disable the part.
2. Low, in addition to disabling the part,
clears the fault flag.
3. High enables the part (if the fault flag is
clear) after a delay time. The delay time
can be calculated by:
delay rise
1
T80ust
3
=+
Enable/Fault pin as an output:
1. The pull up current may (if not over ridden)
allow a “wired nor” pull up to enable the
part.
2. An under voltage will cause a low on the
Enable/Fault pin, and will clear the fault
flag.
3. A thermal fault will cause a mid level on
the Enable/Fault pin, and will set the fault
flag.
The Enable/Fault line must be above the mid
level for the output to be turned on.
The fault flag is an internal flip-flop that can be
set or reset under various conditions:
