MP2009-ULTRA LOW NOISE, LOW DROPOUT,120mA LINEAR REGULATOR
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.
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.
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.
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.
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.
MP2009 Rev. 1.2
12/18/2013
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