MP5010 – 5V, 5A PROGRAMMABLE CURRENT LIMIT SWITCH

MP5010 Rev.0.92

www.MonolithicPower.com

9

9/2/2014

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Current Limit

The desired current limit is a function of the

external current limit resistor.

Table 1—Current Limit vs. Current Limit

Current Limit Resistor (Ω)

22

50

100

Trip Current (A)

3.3

2.0

1.9

Hold Current (A)

2.1

0.9

0.6

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 be shutdown only if the

overcurrent condition stays long enough to

trigger thermal protection.

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 22Ω, the trip current will be 3.3A and

the hold current will be 2.1A. If the device is in

its normal operating state and passing 2.0A it

will need to dissipate only 176mW with the very

low on resistance of 44mΩ. For the package

dissipation of 50°C/Watt, the temperature rise

will only be + 9°C. Combined with a 25°C

ambient, this is only 34°C total package

temperature.

During a short circuit condition, the device now

has 5V across it and the hold current clamps at

2.1A and therefore must dissipate 10.5W. At

50°C/watt, if uncontrolled, the temperature

would

rise

above

the

MP5010

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 feature.

Rise Time

The rise time is a function of the capacitor

(Cdv/dt) on the dv/dt pin.

Table 2—Rise Time vs. Cdv/dt

Cdv/dt

none

50pF

500pF

1nF

Rise Time

(TYPICAL)

(ms)

1.1

2.2

12.3

23.5

The “rise time” is measured by from 10% to

90% of output voltage.

U

90%

10%

Rise Time

t

Input

Output

Enable

Figure 2—Rise Time

Fault and Enable Pin

The Enable/Fault Pin is a Bi-Directional three

levels I/O with a weak pull up current (25uA

typical). The three levels are low, mid and high.

It functions to enable/disable the part and to

relay Fault information.

Enable 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).

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, and will clear the fault

flag.

3. A thermal fault will cause a mid level on

the enable pin, and will set the fault flag.