MP2030 – 3A VERY LOW DROPOUT LINEAR REGULATOR
MP2030 Rev. 0.91 www.MonolithicPower.com 9
10/10/2011 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2011 MPS. All Rights Reserved.
OPERATION
MP2030 Theory of Operation
The MP2030 linear dropout regulator provides
adjustable output voltages from 0.9V to 3.6V at
currents up to 3A. This LDO is protected against
short circuits, and it has thermal shut down
protection with 15
o
C hystheresis.
Utilizing Two Power Supplies
In order to maximize the efficiency MP2030 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 MP2030 has an internal current limit set at
almost 4.5A. When the output current is greater
than 4.5A, current limit is activated, the output
voltage is internally forced close to ground, and
stays at this voltage until the short circuit is
removed. 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
than 1uA from V
BIAS
supply.
If not used then connect this pin to V
BIAS
.
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.
Soft Start
MP2030 incorporates internal soft start function.
This internal function reduces the start up current
surge into the output capacitor. This allows the
gradual built up of output voltage to its final set
value. The internal soft start cap is held to ground
if there is a fault condition. The fault conditions
are UVLO, Thermal shut down, and disable. The
internal soft start time is almost 550us.
Power Good
The Power Good pin is an open drain output and
can be connected to Bias voltage via a pull up
resistor. Open drain transistor turns off and PG
pin voltage value becomes V
BIAS
when V
FB
exceeds 450mV. Also PG pin can sink at least
230μA while being low.
Setting the Output Voltage
The MP2030 has an adjustable output voltage,
set by using a resistive voltage divider from the
output voltage to FB pin. The voltage divider
divides the output voltage down to the feedback
voltage by the ratio:
V
FB
= V
OUT
*R
2
/ (R
1
+R
2
)
Where V
FB
is the feedback threshold voltage
(V
FB
=0.5V), and V
OUT
is the output voltage. R
1
connects between V
OUT
and V
FB
, and R
2
connects
between V
FB
and ground.
Thus the output voltage is:
V
OUT
= 0.5*(R
1
+R
2
)/R
2
R
2
can be as high as 100KΩ, but a typical value
is 10KΩ. Using that value, R
1
is determined by:
R
1
=R
2
x (V
OUT
-V
FB
)/V
FB
For example, for a 1.8V output voltage, R
2
is
10KΩ, and R
1
is 26kΩ. You can select 26kΩ (1%)
resistor for R
1
.
Power Dissipation
Most of the power dissipation is due to power
dissipation in PASS device. For example,
assume V
BIAS
=5.0V, V
IN
=2.0V, V
OUT
=1.8V, and
I
OUT
=3A:
P
D
(
PASS
) = (V
IN
-V
OUT
) x I
OUT
P
D
(
PASS
) = (2.0V-1.8V) x 3A=0.6
