MP20249 – DUAL, ULTRA-LOW NOISE, HIGH PSRR 200mA LINEAR REGULATOR

MP20249 Rev1.0

www.MonolithicPower.com

10

12/15/2010

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© 2010 MPS. All Rights Reserved.

OPERATION

The MP20249 integrates two ultra low noise,

low dropout, low quiescent current and high

PSRR linear regulators for space-restricted

applications. It is intended for use in devices

that require very low voltage, and ultra-small

footprint, such as mobile phones and MP3

players.

The

MP20249

uses

internal

P-channel

MOSFETs as the pass elements and features

internal thermal shutdown and internal current

limit circuits.

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

MP20249 is very low.

Under Voltage Lockout

The MP20249 has an internal under-voltage

lockout circuit that disables the device when the

input voltage is less than approximately 2.1V.

This ensures that the input and the output of the

MP20249 behave in a predictable manner

during input power-up.

EN On / Off

The MP20249 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.

Output Discharge Function

When either channel is disabled, it goes into

output discharge mode automatically and its

internal discharge MOSFET provides a resistive

discharge path for the output capacitor. This

function is only suitable for discharge output

capacitor in the limited time.

Current Limit and Thermal Protection

The MP20249 includes two independent current

limit structures which monitor and control each

P-channel MOSFET’s gate voltage to limit the

guaranteed maximum output current to 200mA.

Thermal protection turns off the P-channel

MOSFETs when the junction temperature

exceeds +150ºC, allowing the IC to cool. When

the IC’s junction temperature drops by 15ºC,

the P-channel MOS will be turned on again.

Thermal protection limits total power dissipation

in the MP20249. For reliable operation, junction

temperature should be limited to 125ºC

maximum.