MCP1700T-3302E 查看數據表（PDF） - Microchip Technology

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MCP1700T-3302E

Low Quiescent Current LDO

Microchip Technology 

6.0 APPLICATION CIRCUITS &

ISSUES

6.1 Typical Application

The MCP1700 is most commonly used as a voltage

regulator. It’s low quiescent current and low dropout

voltage make it ideal for many battery-powered

applications.

VOUT

1.8V

IOUT

150 mA

MCP1700

GND

VIN

VOUT

COUT

1 µF Ceramic

VIN

(2.3V to 3.2V)

CIN

1 µF Ceramic

FIGURE 6-1:

Typical Application Circuit.

6.1.1 APPLICATION INPUT CONDITIONS

Package Type = SOT-23

Input Voltage Range = 2.3V to 3.2V

VIN maximum = 3.2V

VOUT typical = 1.8V

IOUT = 150 mA maximum

6.2 Power Calculations

6.2.1 POWER DISSIPATION

The internal power dissipation of the MCP1700 is a

function of input voltage, output voltage and output

current. The power dissipation, as a result of the

quiescent current draw, is so low, it is insignificant

(1.6 µA x VIN). The following equation can be used to

calculate the internal power dissipation of the LDO.

EQUATION 6-1:

PLDO = (VIN(MAX)) – VOUT(MIN)) × IOUT(MAX))

PLDO = LDO Pass device internal power dissipation

VIN(MAX) = Maximum input voltage

VOUT(MIN) = LDO minimum output voltage

The maximum continuous operating junction

temperature specified for the MCP1700 is +125°C. To

estimate the internal junction temperature of the

MCP1700, the total internal power dissipation is

multiplied by the thermal resistance from junction to

ambient (RθJA). The thermal resistance from junction to

ambient for the SOT-23 pin package is estimated at

230°C/W.

MCP1700

EQUATION 6-2:

TJ(MAX) = PTOTAL × RθJA + TAMAX

TJ(MAX) = Maximum continuous junction

temperature.

PTOTAL = Total device power dissipation.

RθJA = Thermal resistance from junction to ambient.

TAMAX = Maximum ambient temperature.

The maximum power dissipation capability for a

package can be calculated given the junction-to-

ambient thermal resistance and the maximum ambient

temperature for the application. The following equation

can be used to determine the package maximum

internal power dissipation.

EQUATION 6-3:

PD(MAX)

=

-(--T---J---(--M----A---X---)---–-----T----A---(--M----A---X---)--)-

RθJA

PD(MAX) = Maximum device power dissipation.

TJ(MAX) = Maximum continuous junction

temperature.

TA(MAX) = Maximum ambient temperature.

RθJA = Thermal resistance from junction to ambient.

EQUATION 6-4:

TJ(RISE) = PD(MAX) × RθJA

TJ(RISE) = Rise in device junction temperature over

the ambient temperature.

PTOTAL = Maximum device power dissipation.

RθJA = Thermal resistance from junction to ambient.

EQUATION 6-5:

TJ = TJ(RISE) + TA

TJ = Junction Temperature.

TJ(RISE) = Rise in device junction temperature over

the ambient temperature.

TA = Ambient temperature.

© 2007 Microchip Technology Inc.

DS21826B-page 13

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