MP1484 データシートの表示（PDF） - Monolithic Power Systems
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MP1484 Datasheet PDF : 11 Pages
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MP1484 – 3A, 18V, 340KHz SYNCHRONOUS RECTIFIED STEP-DOWN CONVERTER
OPERATION
FUNCTIONAL DESCRIPTION
The MP1484 regulates input voltages from
4.75V to 18V down to an output voltage as low
as 0.925V, and supplies up to 3A of load
current.
The MP1484 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.
The converter uses internal N-Channel
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 FB pin voltage exceeds 20% of the
nominal regulation value of 0.925V, the over
voltage comparator is tripped and the COMP
pin and the SS pin are discharged to GND,
forcing the high-side switch off.
+
1.1V --
FB
+
OVP
RAMP
OSCILLATOR
CLK
340KHz
CURRENT
SENSE
AMPLIFIER +
--
0.3V --
--
SS
+
0.925V +
ERROR
AMPLIFIER
+
SQ
RQ
--
CURRENT
COMPARATOR
IN
5V
BS
SW
COMP
EN
--
2.5V +
+
EN OK
LOCKOUT
COMPARATOR
1.2V
1.5V --
SHUTDOWN
COMPARATOR
Figure 1—Functional Block Diagram
OVP
IN < 4.05V
GND
IN
INTERNAL
REGULATORS
MP1484 Rev. 0.9
www.MonolithicPower.com
5
10/23/2008
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2008 MPS. All Rights Reserved.
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