MP20045 – LOWER NOISE, 1A LINEAR REGULATOR

MP20045 Rev. 1.0

www.MonolithicPower.com

10

10/13/2010

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BLOCK DIAGRA

Figure 1—Block Diagram of Super Low Dropout Regulation

OPERATION

The MP20045 is a low-dropout linear regulator

supplies up to 1A current. It is intended for use

in devices that require very low voltage, low

quiescent, low noise and high PSRR such as

wireless LAN, battery powered equipment and

hand-held equipment.

The MP20045 uses an internal PMOS as the

pass element and features internal thermal

shutdown and internal current limit circuit.

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 MP20045 is very low.

Shutdown

The MP20045 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 MP20045 includes a current limit structures

which monitor and control PMOS’s gate voltage

limiting the guaranteed maximum output current

to 1.2A.

Thermal Protection

Thermal protection turns off the PMOS 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 MP20045. 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 MP20045, 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.