TC1301A datasheet(17/28 Pages) MICROCHIP

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DS21798C-page 17

TC1301A/B

6.0

APPLICATION CIRCUITS/

ISSUES

6.1

Typical Application

The TC1301A/B is used for applications that require

the integration of two LDO’s and a microcontroller

RESET.

FIGURE 6-1:

Typical Application Circuit

TC1301A/B.

6.1.1

APPLICATION INPUT CONDITIONS

6.2

Power Calculations

6.2.1

POWER DISSIPATION

The internal power dissipation within the TC1301A/B is

a function of input voltage, output voltage, output

current and quiescent current. The following equation

can be used to calculate the internal power dissipation

for each LDO.

EQUATION 6-1:

In addition to the LDO pass element power dissipation,

there is power dissipation within the TC1301A/B as a

result of quiescent or ground current. The power

dissipation as a result of the ground current can be

calculated using the following equation. The VIN pin

quiescent current and the VDET pin current are both

considered. The VIN current is a result of LDO

quiescent current, while the VDET current is a result of

the voltage detector current.

EQUATION 6-2:

The total power dissipated within the TC1301A/B is the

sum of the power dissipated in both of the LDO’s and

the P(IGND) term. Because of the CMOS construction,

the typical IGND for the TC1301A/B is 116 µA.

Operating at a maximum of 4.2V results in a power

dissipation of 0.5 milliWatts. For most applications, this

is small compared to the LDO pass device power

dissipation and can be neglected.

The

maximum

continuous

operating

junction

temperature specified for the TC1301A/B is 125°C. To

estimate the internal junction temperature of the

TC1301A/B, the total internal power dissipation is

multiplied by the thermal resistance from junction to

ambient (R

JA) of the device. The thermal resistance

from junction to ambient for the 3x3 DFN8 pin package

is estimated at 41°C/W.

Package Type = 3x3 DFN8

Input Voltage Range = 2.7V to 4.2V

VIN maximum = 4.2V

VIN typical = 3.6V

VOUT1 = 300 mA maximum

VOUT2 = 150 mA maximum

System RESET Load = 10 k

RESET

GND

VDET

BATTERY

COUT1

1µF Ceramic

X5R

CIN

1µF

TC1301A

COUT2

1 µF Ceramic

X5R

Cbypass

10 nF Ceramic

Bypass

VIN

2.7V

4.2V

VOUT2

SHDN2

ON/OFF Control VOUT2

System RESET

2.8V @ 300 mA

1.8V

VOUT1

RESET

BATTERY

COUT1

1 µF Ceramic

X5R

CIN

1µF

TC1301B

COUT2

1µF Ceramic

X5R

Bypass

VIN

2.7V

4.2V

VOUT2

SHDN2

ON/OFF Control VOUT2

System RESET

2.8V @ 300 mA

1.8V

ON/OFF Control VOUT1

VOUT1

@ 150 mA

GND

@ 150 mA

SHDN1

LDO

IN MAX

)

()

OUT MIN

()

–

() I

OUT MAX

)

()

Where:

PLDO

LDO Pass device internal power

dissipation

VIN(MAX)

Maximum input voltage

VOUT(MIN)

LDO minimum output voltage

IGND

()

IN MAX

()

VIN

VDET

()

Where:

PI(GND)

Total current in ground pin

VIN(MAX)

Maximum input voltage

IVIN

Current flowing in the VIN pin with

no output current on either LDO

output

IVDET

Current in the VDET pin with

RESET loaded

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