Micrel, Inc.

MIC94161/2/3/4/5

March 14, 2014

9

Revision 1.1

Application Information

The MIC94161/2/3/4/5 is a family of high-side load

switches designed to operate from 1.7V to 5.5V input

voltage. The load switch pass element is an internal

14.5mΩ R

device to support up to 3A of continuous current.

Additionally, the load switch supports 1.5V logic level

control and shutdown features in a tiny 1.5mm × 1mm

6-ball WLCSP package.

The MIC9416x provides reverse current protection when

the device is disabled. The device will not allow the flow

of current from the output to the input when the device is

turned

OFF.

Additionally,

the

MIC94161

features

overvoltage protection to protect the load when the input

voltage is above 4.55V, as well as a precise enable

threshold which keeps the MIC94161 in the default OFF

state until the EN pin rises above 1.15V.

The MIC94162/3 features rapid turn on for applications

that require quick startup time. The MIC94161/4/5

provides a slew rate controlled soft-start turn-on of 2.7ms.

The soft-start feature is provided to prevent an in-rush

current event from pulling down the input supply voltage.

The MIC94162/4 feature an active load discharge circuit

which switches in a 200Ω load when the switch is

disabled to automatically discharge a capacitive load.

An active pull-down on the enable input keeps the

MIC94161/2/3/4/5 in a default OFF state until the enable

pin is pulled above 1.2V. Internal level shift circuitry

allows low voltage logic signals to switch higher supply

voltages. The enable voltage can be as high as 5.5V and

is not limited by the input voltage.

Power Switch SOA

The safe operating area (SOA) curve represents the

boundary of maximum safe operating current and

maximum safe operating junction temperature.

Figure 3 illustrates the SOA for various input voltages,

with the package mounted on a typical 1 layer, 1 square

inch copper board.

Figure 3. Safe Operating Area (SOA) Graph

Power Dissipation Considerations

As with all power switches, the current rating of the

switch is limited mostly by the thermal properties of the

package and the PCB it is mounted on. There is a simple

ohms law type relationship between thermal resistance,

power dissipation and temperature, which are analogous

to an electrical circuit:

Figure 4. Simple Electrical Circuit

Equation 1:

Eq. 1

Thermal circuits can be considered using these same

rules and can be drawn similarly by replacing current

sources with power dissipation (in watts), resistance with

thermal resistance (in

°C/W) and voltage sources with

temperature (in

°C).

0

0.5

1

1.5

2

2.5

3

3.5

-60 -40 -20

0

20

40

60

80 100 120 140

AMBIENT TEMPERATURE (

°C)

Maximum Current vs.

Ambient Temperature

(1" Square Copper)

VIN = 5v

VIN = 4v5

VIN = 3v6

VIN=2v5