TC1307 datasheet(16/28 Pages) MICROCHIP

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TC1307

DS21702A-page 16

 2002 Microchip Technology Inc.

5.0

APPLICATIONS

5.1

Load Partitioning

The TC1307 can be used to power two separate chan-

nels for a wide range of applications. Each channel can

be turned ON and OFF independently of the other. In

this example, the SELECT12 pin is tied to VIN and the

SELECT34 pin is tied to GND. The output voltages of

VOUT1 and VOUT2 are 3.0V and the output voltage of

VOUT3 and VOUT4 are 1.8V. If VOUT1 and VOUT3 were

powering 1 Channel and VOUT2 and VOUT4 were pow-

ering an identical Channel, either Channel could be

powered independent of the other Channel. The output

voltage of VOUT1 is being monitored by the internal volt-

age detection circuit. When the output of VOUT1 is

below the typical 2.63V threshold voltage, the RESET

output will transition low.

5.2

Input Capacitor

Low input source impedance is necessary for the LDO

to operate properly. When operating off of batteries or

in applications with long lead length (>10”) between the

input source and the LDO, some input capacitance is

required. A minimum of 2.2 µF is recommended for

most applications and the capacitor should be placed

as close to the input of the LDO as practical (>0.2”).

Larger input capacitors will help reduce the input

impedance and further reduce any high frequency

noise on the input and output of the LDO. If more than

1 µF of capacitance is used on the LDO outputs, a

4.7 µF input capacitor is recommended.

5.3

Output Capacitor

A minimum output capacitance of 1 µF for the TC1307

is required for stability. The esr requirements on the

output capacitor are between 0 and 2 ohms. The output

capacitor should be located as close to the LDO output

as practical. Ceramic materials X7R and X5R have low

temperature coefficients and are well within the accept-

able esr range required. A typical 1 µF X5R 0805

capacitor has an esr of 50 milli-ohms. Larger output

capacitors can be used with the TC1307 to improve

dynamic behavior, noise and ripple rejection perfor-

mance.

5.4

Power Dissipation

The internal power loading within the TC1307 is a func-

tion of input voltage, output voltage, output current, qui-

escent current and RESET output dissipation. For

many applications the power dissipation within the lin-

ear P-Channel device can be used as a good approxi-

mation of total power dissipation. This is due to the low

quiescent current consumed even when the LDO out-

put is providing full load current (150 mA).

FIGURE 5-1:

Typical 4 Output with RESET Application.

TC1307

VDET

SHDN1

SHDN3

SHDN4

SHDN2

SELECT12

SELECT34

VIN

RESET

VOUT1

VOUT2

VOUT3

VOUT4

GND

Battery

Input

1µF

4.7 µF

Shutdown #2

Shutdown #1

Shutdown #4

Shutdown #3

Controller

MCLR

RESET

VDD

+3.0V

+1.8V

Micro

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