MP20045 – LOWER NOISE, 1A LINEAR REGULATOR
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.
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.
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.
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.
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.
MP20045 Rev. 0.92
1/4/2010
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