LP6480-01

Apr.-2017

www.lowpowersemi.com

Page 7 of 10

Preliminary Datasheet

LP6480

Operation Information

Functional Description

The LP6480 is a high output current monolithic switch-mode

step-down DC-DC converter. The device operates at a fixed

600KHz switching frequency, and uses a slope compensated

current mode architecture. This step-down DC-DC converter

can supply up to 2A output current at input voltage range from

4.5V to 16V. It minimizes external component size and

optimizes efficiency at the heavy load range. The integrated

slope compensation allows the device to remain stable over a

wider range of inductor values so that smaller values (2.2μH

to 10μH) with lower DCR can be used to achieve higher

efficiency. The device can be programmed with external

feedback to any voltage, ranging from 0.6V to 12V. It uses

internal MOSFETs to achieve high efficiency and can

generate very low output voltages by using an internal

reference of 0.6V. At dropout, the converter duty cycle

increases to 95% and the output voltage tracks the input

MOSFET and the inductor DCR. The internal error amplifier

and compensation provides excellent transient response, load

and line regulation.

Enable The Chip

The enable pin is active high. When pulled low, the enable

input (EN) forces the LP6480 into a low-power, non-switching

state. The total input current during shutdown is less than 6μA.

When apply LP6480 to a circuit, there should be a 500KΩ

resistance between EN and GND.

Current Limit and Over-Temperature Protection

For overload conditions, the peak input current is limited to 3A.

To minimize power dissipation and stresses under current

limit and short-circuit conditions, switching is terminated after

entering current limit condition. The termination lasts for

seven consecutive clock cycles after a current limit has been

sensed

during

a

series

of

four

consecutive

periods of oscillations.

Thermal

protection

completely

disables switching when internal dissipation becomes

excessive. The junction over-temperature threshold is 150℃

with 20℃ of hysteresis. Once an over-temperature or

over-current fault conditions is removed, the output voltage

automatically recovers.

Dropout Operation

When input voltage decreases near the value of the output

voltage, the LP6480 allows the main switch to remain on for

more than one switching cycle and increases the duty cycle

until it reaches 95%. The duty cycle D of a step-down

converter is defined as:

frequency.

Setting the Output Voltage

The LP6480 can be externally programmed. Feedback

resistors R1 and R2 program the output to regulate at a

voltage higher than 0.6V. Although a larger value will further

reduce quiescent current, it will also increase the impedance

of the feedback node, making it more sensitive to external

noise and interference. The minimum suggested value for R1

is 51kΩ. The LP6480, combined with an external feed forward

capacitor, delivers enhanced transient response for extreme

pulsed load applications. The addition of the feed forward

capacitor typically requires a larger output capacitor C2 for

stability. The external resistor sets the output voltage

according to the following equation:

Table1 shows the resistor selection for different output

voltage settings

1.1

100

120.0

1.2

100

100.0

1.3

100

85.7

1.4

100

75.0

1.5

100

66.7

1.8

100

50.0

1.85

100

48.0

2.0

100

42.9

2.5

100

31.6

3.3

100

22.2

Table1: Resistor Selections for Different Output Voltage Settings

(Standard 1% Resistors Substituted For Calculated Values).