MP1593 – 3A, 28V, 385KHz STEP-DOWN CONVERTER
OPERATION
2
IN
CURRENT
SENSE
INTERNAL
REGULATORS
AMPLIFIER
+
--
5V
M1
M2
OSCILLATOR
SLOPE
COMP
1
3
BS
45/385KHz
CLK
+
--
+
S
R
Q
Q
SW
CURRENT
COMPARATOR
SHUTDOWN
COMPARATOR
--
1.2V
7
EN
LOCKOUT
COMPARATOR
--
+
1.8V
2.60V/
2.39V
+
--
4
GND
0.7V 1.22V
5
--
+
FREQUENCY
FOLDBACK
COMPARATOR
ERROR
AMPLIFIER
6
8
FB
COMP
SS
Figure 1—Functional Block Diagram
The MP1593 is a current-mode step-down
regulator. It regulates input voltages from 4.75V to
28V down to an output voltage as low as 1.22V,
and is able to supply up to 3A of continuous load
current.
The converter uses an internal N-Channel
MOSFET switch to step-down the input voltage
to the regulated output voltage. Since the
MOSFET requires a gate voltage greater than
the input voltage, a boost capacitor connected
between SW and BS drives the gate. The
capacitor is internally charged when SW is low.
The MP1593 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 error
An internal 10Ω switch from SW to GND is used
to insure that SW is pulled to GND when it is
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. 1.9
9/14/2006
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5
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