MP2009-ULTRA LOW NOISE, LOW DROPOUT,120mA LINEAR REGULATOR

MP2009 Rev. 1.2

www.MonolithicPower.com

11

12/18/2013

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OPERATION

The MP2009 is an ultra low noise, low dropout,

low-quiescent current linear regulator designed

for space-restricted applications. It is intended for

use in devices that requires very low voltage, low

quiescent current such as wireless LAN, battery-

powered equipment and hand-held equipment.

Internal P-Channel Pass Transistor

The

MP2009

features

a

1.4Ω

P-channel

MOSFET as the pass transistor. It provides

several advantages over similar designs using

PNP pass transistor. The P-channel MOSFET

requires no base drive, which reduces quiescent

current considerably and increase the battery life.

PNP-based

regulators

waste

considerable

current in dropout when the pass transistor

saturates. They also use high base-drive current

under the large load condition. The MP2009 does

not suffer from these problems and consume

only 50µA of quiescent current in light load and

dropout mode.

Dropout Voltage

Dropout voltage is the minimum input to output

differential voltage required for the regulator to

maintain an output voltage within 100mV of its

nominal value. It determines the available end-of-

life battery voltage in battery-powered systems.

For the P-channel MOSFET pass element, the

dropout voltage is a function of drain to source on

resistance. Because the P-channel MOSFET

pass element behaves as a low-value resistor,

the dropout voltage of MP2009 is very low.

Shutdown

The MP2009 can be switched ON or OFF by a

logic input at the EN pin. A high voltage at this

pin will turn the device on. When the EN pin is

low, the regulator output is off. The EN pin should

be tied to VIN to keep the regulator output always

on if the application does not require the

shutdown feature. Do not float the EN pin.

Current Limit and Thermal Protection

The MP2009 includes an independent current

limit structure which monitors and controls the P-

channel MOSFET’s gate voltage to limit the

guaranteed maximum output current to 120mA.

Thermal protection turns off the P-channel

MOSFET when the junction temperature exceeds

+150ºC, allowing the IC to cool. When the IC’s

junction temperature drops by 20ºC, the PMOS

will be turned on again. Thermal protection limits

total power dissipation in the MP2009. For

reliable operation, junction temperature should

be limited to 125 ºC maximum.