MP5011 – 12V, 1A-5A PROGRAMMABLE CURRENT LIMIT SWITCH

MP5011 Rev. 1.01

www.MonolithicPower.com

9

11/8/2013

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OPERATION

Current Limit

The current limit is a function of the external

current limit resistor.

Table 1: Current Limit vs. Current Limit Resistor

(VCC=12V)

Current Limit Resistor (

Ω)

15.4

50

100

Trip Current (A)

5.3

3.4

2.8

Hold Current (A)

4.5

2.1

1.2

If a short is present or the load reaches the trip

current

—the minimum threshold current to trigger

over-current protection (OCP)

—when the part is

active, the part switches into to a constant-

current (hold) mode (CCM). The device shuts

down only if the over-current condition remains

for long enough to trigger thermal protection.

EN, the load current should be smaller than the

current. Otherwise, the part will not completely

turn on.

In a typical application using a current limit

resistor of 15.4

Ω, the trip current is 5.3A and the

hold current is 4.5A. If the device is in its normal

operating state and passing 2.0A it will need to

dissipate only 176mW with a very low ON

resistance of 44

mΩ. For a package dissipation of

50°C/Watt, the temperature rise will only be +9°C;

with 25°C ambient temperature, this amounts to

a total package temperature of 34°C.

In the case of a short-circuit condition, the device

now has 12V across it and the hold current

clamps at 4.5A and therefore must dissipate 44W.

At 50°C/watt, the temperature rises above the

MP5011

thermal

protection

(175°C)

if

left

unchecked and device shutdown allows the

temperature to drop below a hysteresis level.

Use an appropriate heat sink if the device is

intended to supply the hold current and not

shutdown. Without a heat sink, maintain the hold

current below 250mA at 25°C and below 150mA

at 85°C to prevent the device from activating the

thermal shutdown feature.

Figure 2

Rise Time

on the dv/dt pin.

None

33pF

470pF

1nF

Rise Time

(

Typ) (ms)

1.4

2.0

11.6

22.5

The rise time is measured by from 10% to 90% of

output voltage.

Figure 3

Enable / Fault Pin

The Enable/Fault pin is a bi-directional, three-

level I/O with a weak pull-up current (typically

25µA). There are three levels: low, mid, and high.

It enables/disables the part and relays fault

information.

When the Enable/Fault pin is an input:

1.

Low and mid levels disable the part.

2.

Low clears the fault flag in addition to

disabling the part.

3.

High enables the part (if the fault flag is

clear).