MP1593 – 3A, 28V, 385kHz STEP-DOWN CONVERTER
OPERATION
IN 2
INTERNAL
REGULATORS
OSCILLATOR
SLOPE
COMP
CLK
CURRENT
SENSE
AMPLIFIER
+
--
M1
5V
45/385KHz
+
1
Q
Q
BS
+
S
R
1.2V
EN 7
--
SHUTDOWN
COMPARATOR
LOCKOUT
COMPARATOR
--
CURRENT
COMPARATOR
3
M2
1.8V
SW
--
2.60V/
2.39V
+
+
--
4
GND
FREQUENCY
FOLDBACK
COMPARATOR
--
0.7V
5
1.22V
FB
+
ERROR
AMPLIFIER
6
COMP
8
SS
Figure 1—Functional Block Diagram
The converter uses an internal N-Channel
The MP1593 is a current-mode step-down
MOSFET switch to step-down the input voltage
regulator. It regulates input voltages from 4.75V to
to the regulated output voltage. Since the
28V down to an output voltage as low as 1.22V,
MOSFET requires a gate voltage greater than
and is able to supply up to 3A of continuous load
the input voltage, a boost capacitor connected
current.
between SW and BS drives the gate. The
The MP1593 uses current-mode control to
capacitor is internally charged when SW is low.
regulate the output voltage. The output voltage
An internal 10Ω switch from SW to GND is used
is measured at FB through a resistive voltage
to insure that SW is pulled to GND when it is
divider and amplified through the internal error
low to fully charge the BS capacitor.
amplifier.
The
output
current
of
the
transconductance error amplifier is presented at
COMP where a network compensates the
regulation control system. The voltage at COMP
is compared to the internally measured switch
current to control the output voltage.
MP1593 Rev. 2.11
1/10/2013
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
6
MPS [ MONOLITHIC POWER SYSTEMS ]
