MP2040 –FAST TRANSIENT RESPONSE, 3A VERY LOW DROPOUT LINEAR REGULATOR

MP2040 Rev.1.0

www.MonolithicPower.com

8

9/21/2010

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BLOCK DIAGRAM

BYPASS

BIAS

EN

GND

PGOOD

O

FB

VOUT

VIN

+

--

0.5V

0.45V

REFERENCE

SOFT

START

GATE

--

+

Figure 1—Block Diagram of Low Dropout Regulator

OPERATION

MP2040 Theory of Operation

The MP2040 linear dropout regulator provides

adjustable output voltages from 0.9V to 3.3V at

currents up to 3A. This LDO is protected against

short circuits, and it has thermal shut down

Utilizing Two Power Supplies

In order to maximize the efficiency MP2040 uses

two power supplies. One power supply is

connected to the BIAS pin and it is used to power

up the internal circuitries including band gap

reference and the rest of control circuitries. The

other power supply is connected to the VIN pins

which are the drain of pass device. This power

supply can be set close to output voltage of LDO.

The output pins are the source of the pass

device. The smaller voltage drop across the pass

device translates to the smaller power loss in

pass device. Thus, the part operates with higher

efficiency.

Internal Current Limit

The MP2040 has an internal current limit set at

almost 3.8A. Internal current limit is very well

controlled over process variations and ambient

temperature.

Enable

The enable (EN) pin is active high. The enable

pin has a built-in hystheresis. If this pin is held

below 0.8V then part shuts down and draws less

Under Voltage Lockout

The Bias voltage is monitored by a circuit that

prevents the LDO start up when the bias voltage

is below 2.35V. This circuitry has an approximate

hystheresis of 90mV.