MP5006 – 5V, 1A- 5A PROGRAMMABLE CURRENT LIMIT SWITCH WITH AUTO ENABLE
MP5006 Rev.0.92 www.MonolithicPower.com 11
12/27/2013 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
THERMAL PROTECTION
The MP5006 only considers a thermal overload
to be a fault. Under a fault condition the mp5006
will have two actions:
1) Turn off the output power device.
2) Drive the enable/fault pin to the low level.
The power device will remain off until the die
temperature drops below the hysteresis level.
When the die cools down below the thermal
hysteresis level, the MP5006 will restart in the
start up mode and the fault line will be pulled high
through a 25uA pull up current. If the cause of
the fault has been removed, the output will ramp
up in a controlled fashion with the ramp rate
controlled by the dv/dt function. If the cause of
the fault is still present, the excess power
dissipation will heat up the part. When the die
temperature reaches the thermal shutdown
temperature, the output will be turned off and the
enable/fault pin will be driven to the low level,
again. This cycle will repeat until the cause of the
fault is removed.
Figure 3Thermal Protection in Short Condition
The drawing above shows the initial start up
sequence and the occurrence of a short at the
output.
At time T0 the input voltage begins to rise. At T1
the input voltage rises above the UVLO threshold
and the part starts up. The output current ramps
up and settles at the normal operating current
level until time T2. There is a very small
temperature heating of the die in normal
operation.
At time T2 the output is shorted. This brings the
output very close to ground. The output current
increases to the current limit level and is held
there by the MP5006. Because of the large
current and the large voltage across the power
device, the die will begin to heat up.
At time T3 the die temperature is at the thermal
shutdown level and the part will turn the power
device off. The enable/fault pin is driven to the
low level. Once the power device is off, the die
temperature will begin to drop.
At time T4 the part has cooled down below the
thermal hysteresis level. The enable pin goes
high and the part turns on again. But the short is
still present, causing the die temperature to
increase.
