MIC47050YMT datasheet(11/16 Pages) MICREL

Part #	MIC47050YMT

Description	500mA ULDO??with Low Input and Low Output Voltage

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Manufacturer	MICREL [Micrel Semiconductor]

Direct Link	http://www.micrel.com

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Micrel, Inc.

MIC47050

April 2012

11

M9999-040312-B

Power Good (PGOOD)

The Power Good (PGOOD) pin is an open drain output

that goes low when the output voltage (fixed version)

drops below the PGOOD threshold voltage.

The pull-up resistor value should be large enough to

guarantee a proper “low” voltage when the PGOOD pin

pulls low. The PGOOD low voltage is typically 0.1V at

250µA current. A 10kΩ resistor or

greater

is

recommended when pulling up to 3.3V bias.

If the PGOOD function is not required, the PGOOD pin

may be left unconnected.

Thermal Shutdown

The MIC47050 has an internal over-temperature

protection feature. This feature is for protection only.

The device should never be intentionally operated near

this temperature as this may reduce long term reliability.

The device will turn off when the over-temperature

threshold is exceeded. A 20°C hysteresis is built in to

allow the device to cool before turning back on.

Thermal Considerations

The MIC47050 is designed to provide 0.5A of continuous

current in a very small package. Maximum ambient

operating temperature can be calculated based on the

output current and the voltage drop across the part.

Given that the input voltage is 1.8V, the output voltage is

1.2V and the output current is 0.5A. The actual power

dissipation of the regulator circuit can be determined

using the equation:





BIAS

I

BIAS

V

GND

I

IN

V

OUT

I

OUT

V

IN

V

D

P















Because this device is CMOS, the ground current is

insignificant for power dissipation and can be ignored for

this calculation.



0.3W

0.5A

1.2V

1.8V

D

P









To

determine

the

maximum

ambient

operating

temperature of the package, use the junction-to-ambient

thermal resistance of the device and the following basic

equation:

















JA

Θ

A

T

J(MAX)

T

D(MAX)

P

TJ(MAX) = 125°C, the maximum junction temperature of

the die.

θJA thermal resistance = 90°C/W.

Table 1 shows junction-to-ambient thermal resistance for

the MIC47050 in the MLF

® or Thin MLF® package.

Package

θJA Recommended

Min. Footprint

θJC

6-pin 2mm x 2mm MLF

®

90°C/W

45°C/W

6-pin 2mm x 2mm

Thin MLF

®

90°C/W

45°C/W

Table 1. Thermal Resistance

Substituting PD for PD(max) and solving for the ambient

operating temperature will give the maximum operating

conditions for the regulator circuit. The junction-to-

ambient thermal resistance for the minimum footprint is

90°C/W. The maximum power dissipation must not be

exceeded for proper operation. For example, when

operating the MIC47050-1.2YML at an input voltage of

1.8V and a 0.5A load with a minimum footprint layout,

the maximum ambient operating temperature TA can be

determined as follows:

C

98

A

T

0.3W

C/W

90

C

125

A

T

D(MAX)

P

JA

Θ

J(MAX)

T

A

T





















Therefore, a 1.2V application with 0.5A of output current

can accept an ambient operating temperature of 98°C in

a 2mm x 2mm MLF

® or Thin MLF® package.

Thermal Measurements

Measuring the IC’s case temperature is recommended to

insure it is within its operating limits. Although this might

seem like a very elementary task, it is easy to get

erroneous results. The most common mistake is to use

the standard thermal couple that comes with a thermal

meter. This thermal couple wire gauge is large, typically

22 gauge, and behaves like a heatsink, resulting in a

lower case measurement.

Two methods of temperature measurement are using a

smaller thermal couple wire or an infrared thermometer.

If a thermal couple wire is used, it must be constructed

of 36 gauge wire or higher (smaller wire size) to

minimize the wire heat-sinking effect.

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