LP6490 datasheet(5/6 Pages) POWER

5 / 6 page

LP6490-01

Jun.-2017

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Page 5 of 6

Preliminary Datasheet

LP6490

Application Information

The LP6490 operates by a constant frequency,

current mode architecture. The output voltage is set

by an external divider returned to the FB pin. An error

amplifier compares the divided output voltage with a

reference voltage of 0.6V and adjusts the peak

inductor current accordingly.

Thermal Protection

The total power dissipation in LP6490 is limited by a

thermal protection circuit. When the device

temperature rises to approximately 150℃, this circuit

turns off the output, allowing the IC to cool. The

thermal protection circuit can protect the device from

being damaged by overheating in the event of fault

conditions. Continuously running the LP6490 into

thermal shutdown degrades device reliability.

Current Limit

The Current limit is set by outside resistance (RSEN),

When the CS voltage larger than 64mV, the current

limit is happened that driver can be turned off. The

current limit set according to the following equation:

IOUT=VCS/RSEN

Setting Output Voltage

The output voltage is set with a resistor divider from

the output node to the FB pin. It is recommended to

use divider resistors with 1% tolerance or better. To

improve efficiency at very light loads consider using

larger value resistors. If the values are too high the

regulator is more susceptible to noise and voltage

errors from the FB input current are noticeable. For

most applications, a resistor in the 10kΩ to 1MΩ

range is suggested for RUP and RDN. The output

voltage is established by the following equations

VOUT=0.6V×(1+RUP/RDN)

Where VREF is 0.6V.

Output Cable Resistance Compensation

To compensate for resistive voltage drop across the

charger's output cable, the LP6490 integrates a

simple, user-programmable cable voltage drop

compensation using the impedance at the FB pin.

The delta VOUT rises when the feedback resistance

RSEN value rises, use the equation below:

ΔVOUT=IOUT×RSEN×RUP/10KΩ

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