LP6470T-01

Aug.-2017

www.lowpowersemi.com

Page 7 of 10

Preliminary Datasheet

LP6470T

General Description

Functional Description

The LP6470T 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

3.5V 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 0.766V to 12V. It uses

internal MOSFETs to achieve high efficiency and can

generate very low output voltages by using an internal

reference of 0.766V. 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 LP6470T into a low-power,

non-switching state. The total input current during shutdown is

less than 1μA. When apply LP6470T to a circuit, there should

be a 100KΩ 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 LP6470T 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 LP6470T can be externally programmed. Feedback

voltage higher than 0.766V. 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. For achieving circuit loop

LP6470T, combined with an external feed forward capacitor,

delivers enhanced transient response for extreme pulsed load

applications. The addition of the feed forward capacitor

external resistor sets the output voltage according to the

following equation:

Table1 shows the resistor selection for different output

voltage settings

1.1

100

229.3

1.2

100

176.5

1.3

100

143.4

1.4

100

120.8

1.5

100

104.4

1.8

100

74.1

1.85

100

70.7

2.0

100

62.1

2.5

100

44.2

3.3

100

30.2

Table1: Resistor Selections for Different Output Voltage

Settings (Standard 1% Resistors Substituted For Calculated

Values).