MP5077 – 5.5V, 7A, LOW RDSON LOAD SWITCH WITH PROGRAMMABLE CURRENT LIMIT

MP5077 Rev. 1.01

www.MonolithicPower.com

12

6/23/2014

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APPLICATION INFORMATION

ILIM Resistor Selection

The current limit value can be set by ILIM

resistor. The current limit can be gotten by

equation (1).

The current limit threshold is suggested to 10%

~ 20% higher than maximum load current. For

example, if the system’s full load is 7A, set the

current limit to 7.7A.

Soft Start Capacitor Selection

There is an internal 9

μA constant current

source charge SS cap and ramps up the

voltage on the SS pin. The output voltage rises

follow 3 times the slew rate of SS voltage.

If the inrush on output current reached the

current limit during start up (like with large

output cap or very large load), MP5077 will limit

the output current and the same time, SS time

will be increased (Figure 2 and Figure 3).

Soft Start @ Different Load

Soft Start @ No Load

Soft Start @ Half Load

Soft Start @ Very large Load

Current Limit

Current Limit

Current Limit

Figure 2: Soft Start Periods at different load

Soft Start @ Different Output Capacitance

Soft Start @ Small Capacitance

Soft Start @ Large Capacitance

Soft Start @ Very large

Capacitance

Current Limit

Current Limit

Current Limit

Figure 3: Soft Start Periods at different output

capacitance

Design Example

Some design example and are provided below.

See Table 1 and Figure 4.

Table 1

Vin

(V)

Max Load Range

(A)

Rlimit

(kΩ)

SS cap

(nF)

SS time

(ms)

5

3

26.1

22

4

5

5

15.8

47

9

5

7.5

10.5

100

20