MP1482 MPS, MP1482 Datasheet - Page 6

• Manufacturer Part Number: MP1482
• Description: 2a, 18v Synchronous Rectified Step-down Converter
• Manufacturer: MPS

OPERATION
FUNCTIONAL DESCRIPTION
The MP1482 is a synchronous rectified,
current-mode, step-down regulator. It regulates
input voltages from 4.75V to 18V down to an
output voltage as low as 0.923V, and supplies
up to 2A of load current.
The MP1482 uses current-mode control to
regulate the output voltage. The output voltage
is measured at FB through a resistive voltage
divider and amplified through the internal
transconductance error amplifier. The voltage at
the COMP pin is compared to the switch current
measured internally to control the output
voltage.
MP1482 Rev. 1.2
1/13/2010
COMP
EN
SS
FB
0.923V
1.1V
0.3V
2.5V
1.5V
+
--
+
--
--
+
+
--
+
+
--
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
MP1482 – 2A, 18V SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER
COMPARATOR
COMPARATOR
SHUTDOWN
AMPLIFIER
LOCKOUT
ERROR
EN OK
Figure 1—Functional Block Diagram
OVP
OSCILLATOR
340KHz
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www.MonolithicPower.com
RAMP
CLK
1.2V
+
--
The
MOSFET switches to step-down the input
voltage to the regulated output voltage. Since
the high side MOSFET requires a gate voltage
greater than the input voltage, a boost capacitor
connected between SW and BS is needed to
drive the high side gate. The boost capacitor is
charged from the internal 5V rail when SW is low.
When the MP1482 FB pin exceeds 20% of the
nominal regulation voltage of 0.923V, the over
voltage comparator is tripped and the COMP
pin and the SS pin are discharged to GND,
forcing the high-side switch off.
COMPARATOR
CURRENT
converter
R
S
AMPLIFIER
CURRENT
SENSE
Q
Q
uses
REGULATORS
+
--
INTERNAL
internal
IN
OVP
IN < 4.1V
5V
N-Channel
IN
BS
SW
GND
6