TC2014 Ver la hoja de datos (PDF) - Microchip Technology

Número de pieza

componentes Descripción

Fabricante

TC2014

50 mA, 100 mA, 150 mA CMOS LDOs with Shutdown and Reference Bypass

Microchip Technology 

5.0 THERMAL CONSIDERATIONS

5.1 Thermal Shutdown

Integrated thermal protection circuitry shuts the regula-

tor off when the die temperature exceeds approxi-

mately 160°C. The regulator remains off until the die

temperature cools to approximatley 150°C.

5.2 Power Dissipation

The amount of power the regulator dissipates is primar-

ily a function of input voltage, output voltage and output

current.

The following equation is used to calculate worst-case

power dissipation.

EQUATION 5-1:

PD  VINMAX – VOUTMINILMAX

Where:

PD

= Worst-case actual power dissipation

VINMAX = Maximum voltage on VIN

VOUTMIN = Minimum regulator output voltage

ILMAX = Maximum output (load) current

The maximum allowable power dissipation (PDMAX) is

a function of the maximum ambient temperature

(TAMAX), the maximum allowable die temperature

(TJMAX) (+125°C) and the thermal resistance from junc-

tion-to-air (JA). The 5-Pin SOT-23A package has a JA

of approximately 220°C/Watt when mounted on a

typical two-layer FR4 dielectric copper-clad PC board.

EQUATION 5-2:

PDMAX = T----J---M----A---X----–-J---A-T---A----M----A---X-

Where all terms are previously defined.

TC2014/2015/2185

The PD equation can be used in conjunction with the

PDMAX equation to ensure that regulator thermal

operation is within limits. For example:

Given:

VINMAX

VOUTMIN

ILOADMAX

TJMAX

TAMAX

= 3.0V +10%

= 2.7V – 2.5%

= 40 mA

= +125°C

= +55°C

Find:

1. Actual power dissipation

2. Maximum allowable dissipation

Actual power dissipation:

PD = VINMAX – VOUTMINILMAX

= 3.0  1.1 – 2.7  0.97540  10–3

= 26.7mW

Maximum allowable power dissipation:

PDMAX = T----J--M-----A---X----–-J---A-T---A----M----A---X-

= 1----2---5----–-----5---5-

220

= 318mW

In this example, the TC2014 dissipates a maximum of

only 26.7 mW; far below the allowable limit of 318 mW.

In a similar manner, the PD and PDMAX equations can

be used to calculate maximum current and/or input

voltage limits.

5.3 Layout Considerations

The primary path of heat conduction out of the package

is via the package leads. Therefore, layouts having a

ground plane, wide traces at the pads and wide power

supply bus lines combine to lower JA and, therefore,

increase the maximum allowable power dissipation

limit.

 2001-2012 Microchip Technology Inc.

DS21662F-page 11

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