TM
MP1591 – 2A, 32V, 330KHz STEP-DOWN CONVERTER
OPERATION
The MP1591 is a current mode step-down
regulator. It regulates input voltages from 6.5V
to 32V down to an output voltage as low as
1.230V and is able to supply up to 2A of load
current.
The MP1591 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
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 switch
current measured internally to control the output
voltage. 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 while SW is
low. An internal 10Ω switch from SW to GND is
used to insure that SW is pulled to GND when
the switch is off to fully charge the BS capacitor.
IN 2
REF 8
5V
INTERNAL
REGULATORS
OSCILLATOR
SLOPE
COMP
CLK
CURRENT
SENSE
AMPLIFIER
+
--
M1
35/330KHz
+
1
Q
Q
BS
+
S
R
1.2V
EN 7
--
SHUTDOWN
COMPARATOR
LOCKOUT
COMPARATOR
--
CURRENT
COMPARATOR
3
M2
SW
--
2.60V/
2.35V
1.8V
+
--
4
GND
+
FREQUENCY
FOLDBACK
COMPARATOR
--
0.7V 1.230V
5
FB
+
ERROR
AMPLIFIER
6
COMP
MP1591_BD01
Figure 1—Functional Block Diagram
MP1591 Rev. 1.8
7/22/2005
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