ncp1540 ON Semiconductor, ncp1540 Datasheet - Page 5

• Manufacturer Part Number: ncp1540
• Description: 3.5 A High Efficiency Step-down Dc-dc Converter
• Manufacturer: ON Semiconductor

regulates input voltages from 4.5 V to 28 V down to an
output voltage as low as 1.2 V, and is able to supply up to
3.5 A of continuous load current.
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
The NCP1540 is a current-mode step-down regulator. It
The NCP1540 uses current-mode control to regulate the
DETAILED DESCRIPTION
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NCP1540
5
system. The voltage at COMP is compared to the internally
measured switch current 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 LX and BST drives the gate. The capacitor is
internally charged when LX is low. An internal 6 W switch
from LX to GND is used to insure that LX is pulled to GND
when it is low to fully charge the BST capacitor.