XRP6274

2A Ultra Low Dropout Voltage Regulator

© 2015 Exar Corporation

7/11

Rev. 2.0.0

THEORY OF OPERATION

The XRP6274’s ultra low input voltage allows

single rail operation from 2.625V down to

1.045V without requiring any extra biasing

voltage. This single input voltage range

provides easy conversions from industry

standard 1.1V, 1.2V, 1.35V, 1.5V, 1.8V and

2.5V power rails.

The dropout voltage is the input-to-output

differential voltage at which the XRP6274

ceases to regulate against further reductions in

input voltage; this point occurs when the input

voltage approaches the output voltage. The

XRP6274 provides ultra low industry leading

dropout voltage performance making it the

perfect solution for high current extremely tight

input/output

voltage

conversions.

This

extremely low dropout voltage allows high

efficiencies conversions.

Below

tables

illustrate

the

achievable

conversions for different load requirements for

the XRP6274.

2A

VIN (V)

1.80

1.50

1.35

1.20

1.10

1.00

0.90

0.80

0.60

2.50

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

1.80

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

1.50

No

Yes

Yes

Yes

Yes

Yes

Yes

1.35

No

Yes

Yes

Yes

Yes

Yes

1.20

No

Yes

Yes

Yes

Yes

1.10

No

Yes

Yes

Yes

Output Voltage

Note: Yellow indicates conversions that may be thermally

limited

The maximum output current available for a

given conversion is dependent on the operating

conditions

and

thermal

performance

of

DFN10/PCB (see note 1 on page 3).

The XRP6274 is an adjustable regulator that

can be programmed to any value between 0.6V

and 2.4V using 2 external resistors, R1 and R2.

The relationship between the resistors and the

output voltage is:

0.6

− 1)

Sum of resistors R1 and R2 must meet the

following requirement:

����1 + ����2

≥ 20��������

The XRP6274 is designed to be stable for all

available types and values of output capacitors

greater than 4.7µF.

pins strongly depends on the input supply

source

impedance;

the

minimum

recommended capacitor for VIN is 4.7µF. Low

ESR ceramic X5R and X7R capacitors are

recommended and should be placed as close as

possible to the pins for optimal performance.

Because of the low voltages and high currents

supported by this device, typical values of 47uF

for both input and output capacitors are

recommended when powering high speed

digital circuits.

The enable pin (EN) can be used to shut down

the XRP6274. Connecting this pin to ground

signal or to a voltage less than typical 0.55V will

completely turn off the regulator. Pulling the EN

above 0.67V enables the XRP6274. Where EN

is derived from VIN it must be sequenced with

respect to VIN as shown in the application

circuit. Where an independent control signal is

applied to EN, it must be asserted high after

VIN reaches its minimum operating range.

The enable pin is a high impedance MOS input.

In order to allow the EN pin compatibility with

5V or 3.3V control signals, there is an internal

clamp set to VIN+0.5V. When using the EN pin

with a control signal greater than VIN+0.5V, a

resistor must be placed in series with the EN pin

to limit the input current below 100uA. The

resistor must also be low enough to ensure at

least 15uA can be sourced to enable the part.

The

precision

feature

enables

simple

sequencing of multiple power supplies with a

resistor divider from another power supply or

power good flag. The EN pin can also be used

as an external UVLO to disable the part when