TM
MP2303 – 3A, 28V, 340KHz SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER
INITIAL RELEASE – SPECIFICATIONS SUBJECT TO CHANGE
OPERATION
+
OVP
0.95V
FB
0.3V
--
OSCILLATOR
+
340KHz
--
--
--
SS
0.8V
+
+
ERROR
AMPLIFIER
+
S
R
Q
Q
SW
RAMP
CLK
CURRENT
SENSE
AMPLIFIER
IN
+
--
BS
5V
CURRENT
COMPARATOR
COMP
EN
2.5V
--
GND
EN OK
LOCKOUT
COMPARATOR
1.2V
OVP
IN < 4.05V
IN
+
INTERNAL
REGULATORS
1.5V
--
SHUTDOWN
COMPARATOR
MP2303_BD01
+
Figure 1—Functional Block Diagram
The MP2303 is a synchronous rectified,
current-mode, step-down regulator. It regulates
input voltages from 4.75V to 28V down to an
output voltage as low as 0.8V, and supplies up
to 3A of load current.
The MP2303 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
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 MP2303 FB pin exceeds 20% of the
nominal regulation voltage of 0.8V, the over
voltage comparator is tripped; the COMP pin
and the SS pin are discharged to GND, forcing
the high-side switch off.
MP2303 Rev. 0.92
5/2/2006
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