MP5006 – 5V, 1A- 5A PROGRAMMABLE CURRENT LIMIT SWITCH WITH AUTO ENABLE
MP5006 Rev.0.92 www.MonolithicPower.com 9
12/27/2013 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
CURRENT LIMIT
The desired current limit is a function of the
external current limit resistor.
Table 1Current Limit vs. Current Limit Resistor
(V
IN
=5V)
Current Limit Resistor
()
24 50 75 100
Trip Current
(A)
3 2 1.78 1.67
Hold Current
(A)
1.55 0.76 0.5 0.38
When the part is active, if load reaches trip
current (minimum threshold current triggering
overcurrent protection) or a short is present, the
part switches into to a constant-current (hold
current) mode. Part will enter thermal cycling only
if the overcurrent 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 24, the trip current will be 3A and the
hold current will be 1.55A. If the device is in its
normal operating state and passing 1.55A it will
need to dissipate only 105.7mW with the very low
on resistance of 44m. For the package
dissipation of 50°C/Watt, the temperature rise will
only be + 5.3°C. Combined with a 25°C ambient,
this is only 30.3°C total package temperature.
During a short circuit condition, the device now
has 5V across it and the hold current clamps at
1.55A and therefore must dissipate 7.75W. At
50°C/watt, if uncontrolled, the temperature would
rise above the MP5006 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 600mA at + 25°C
and below 360mA at +85°C to prevent the device
from activating the thermal shutdown.
RISE TIME
The rise time is a function of the capacitor (C
dv/dt
)
on the dv/dt pin.
Table 2Rise Time vs. Cdv/dt
C
dv/dt
none 50pF 500pF 1nF
Rise Time*
(TYPICAL)
(ms)
1.1 2.2 12.3 23.5
* Notes: Rise Time = K
RT
*(50pF+Cdv/dt), K
RT
=22E6
The “rise time” is measured by from 10% to 90%
of output voltage.
U
90%
10%
Rise Time
t
Input
Output
Enable
Figure 2Rise Time
FAULT AND ENABLE PIN
The Enable/Fault Pin is a Bi-Directional I/O with a
weak pull up current (25uA typical). It functions to
enable/disable the part.
Enable pin as an input:
1. Low disables the part.
2. High enables the part.
Enable 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 pin.
3. A thermal fault will cause a low level on
the enable pin.
