MCP1703AT-1202ESLASHMB datasheet(12/31 Pages) MICROCHIP

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MCP1703A

DS20005122B-page 12

 2012-2013 Microchip Technology Inc.

4.0

DETAILED DESCRIPTION

4.1

Output Regulation

A portion of the LDO output voltage is fed back to the

internal error amplifier and compared with the precision

internal band gap reference. The error amplifier output

adjusts the amount of current that flows through the P-

Channel pass transistor, thus regulating the output

voltage to the desired value. Any changes in input

voltage or output current causes the error amplifier to

respond and adjust the output voltage to the target

voltage (see Figure 4-1).

4.2

Overcurrent

The MCP1703A internal circuitry monitors the amount

of current flowing through the P-Channel pass

transistor. In the event of a short-circuit or excessive

output current, the MCP1703A turns off the P-Channel

device for a short period, after which the LDO attempts

to restart. If the excessive current remains, the cycle

will repeat itself.

4.3

Overtemperature

The internal power dissipation within the LDO is a

function of input-to-output voltage differential and load

current. If the power dissipation within the LDO is

excessive, the internal junction temperature rises

above the typical shutdown threshold of 150°C. At that

point, the LDO shuts down and begins to cool to the

typical turn-on junction temperature of 130°C. If the

power dissipation is low enough, the device will

continue to cool and operate normally. If the power

dissipation remains high, the thermal shutdown

protection circuitry will again turn off the LDO,

protecting it from catastrophic failure.

FIGURE 4-1:

Block Diagram.

VIN

VOUT

GND

+VIN

Error Amplifier

Voltage

Reference

Overcurrent

Overtemperature

MCP1703A

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