MP20044-DUAL, ULTRA LOW NOISE, HIGH PSRR, 300mA LINEAR REGULATOR

MP20044 Rev. 1.0

www.MonolithicPower.com

8

1/11/2013

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BLOCK DIAGRAM

Figure1—Functional Block Diagram

OPERATION

The MP20044 integrates two low noise, low

dropout, low quiescent current and high PSRR

linear regulators. It is intended for use in devices

that require very low voltage, low quiescent

current power such as wireless LAN, battery-

powered equipment and hand-held equipment.

The MP20044 uses internal PMOSs 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. Because the PMOS pass element

behaves as a low-value resistor, the dropout

voltage of MP20044 is very low.

Shutdown

The MP20044 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

The MP20044 includes two independent current

limit structures which monitor and control each

PMOS’s gate voltage limiting the guaranteed

maximum output current to 300mA.

Thermal Protection

Thermal protection turns off the PMOS when the

junction temperature exceeds +140ºC, allowing

the IC to cool. When the IC’s junction

temperature drops by 10ºC, the PMOS will be

turned on again. Thermal protection limits total

power dissipation in the MP20044. For reliable

operation, junction temperature should be limited

to 125 ºC maximum.

Load-Transient Considerations

The output response of load-transient consists of

a DC shift and transient response. Because of

the excellent load regulation of MP20044, the DC

shift is very small. The output voltage transient

depends on the output capacitor’s value and the

ESR. Increasing the capacitance and decreasing

the ESR will improve the transient response.

Typical

output

voltage

transient

spike

of

MP20044 for a step change in the load current

from 10mA to 100mA is tens mV.