MP20249 – DUAL, ULTRA-LOW NOISE, HIGH PSRR 200mA LINEAR REGULATOR
MP20249 Rev1.0 www.MonolithicPower.com 10
12/15/2010 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 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.
