MCP1703A datasheet(13/30 Pages) MICROCHIP

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DS25122A-page 13

MCP1703A

5.0

FUNCTIONAL DESCRIPTION

The MCP1703A CMOS low dropout linear regulator is

intended for applications that need the lowest current

consumption

while

maintaining

output

voltage

regulation. The operating continuous load range of the

MCP1703A is from 0 mA to 250 mA (VR ≥ 2.5V). The

input operating voltage range is from 2.7V to 16.0V,

making it capable of operating from two or more

alkaline cells or single and multiple Li-Ion cell batteries.

5.1

Input

The input of the MCP1703A is connected to the source

of the P-Channel PMOS pass transistor. As with all

LDO circuits, a relatively low source impedance (10

Ω)

is needed to prevent the input impedance from causing

the LDO to become unstable. The size and type of the

capacitor needed depends heavily on the input source

type (battery, power supply) and the output current

range of the application. For most applications (up to

100 mA), a 1 µF ceramic capacitor will be sufficient to

ensure circuit stability. Larger values can be used to

improve circuit AC performance. The capacitance of

the input capacitor should be equal to or greater than

the capacitance of the selected output capacitor to

ensure energy is available to keep the output capacitor

charged during dynamic load changes.

5.2

Output

The maximum rated continuous output current for the

MCP1703A is 250 mA (VR ≥ 2.5V). For applications

where VR < 2.5V, the maximum output current is

200 mA.

A minimum output capacitance of 1.0 µF is required for

small signal stability in applications that have up to

250 mA output current capability. The capacitor type

can be ceramic, tantalum, or aluminum electrolytic. The

Equivalent Series Resistance (ESR) range on the

output capacitor can range from 0

Ω to 2.0Ω.

The output capacitor range for ceramic capacitors is

1 µF to 22 µF. Higher output capacitance values may

be used for tantalum and electrolytic capacitors. Higher

output capacitor values pull the pole of the LDO

transfer function inward that results in higher phase

shifts which in turn cause a lower crossover frequency.

The circuit designer should verify the stability by

applying line step and load step testing to their system

when using capacitance values greater than 22 µF.

5.3

Output Rise Time

When powering up the internal reference output, the

typical output rise time of 600 µs is controlled to

prevent overshoot of the output voltage.

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