XRP6274 Datasheet, PDF (7/11 Pages) Exar Corporation – 2A Ultra Low Dropout Voltage Regulator

XRP6274
2A Ultra Low Dropout Voltage Regulator
THEORY OF OPERATION
SINGLE RAIL INPUT VOLTAGE
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.
DROPOUT VOLTAGE
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
Output Voltage
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
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).
SETTING THE OUTPUT VOLTAGE
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:
𝑅₁ = 𝑅₂ × (𝑉0^𝑂_.^í µ₆^{í±ˆí µí±‡} − 1)
where VOUT is the desired output voltage.
Sum of resistors R1 and R2 must meet the
following requirement:
𝑉_{𝑂𝑈𝑇}
𝑅1 + 𝑅2
≥
20𝑚𝐴
INPUT AND OUTPUT CAPACITORS
The XRP6274 is designed to be stable for all
available types and values of output capacitors
greater than 4.7µF.
The required capacitance on the VIN and VOUT
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.
ENABLE INPUT AND SHUTDOWN
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
© 2015 Exar Corporation
7/11
Rev. 2.0.0