LP6230A datasheet(6/7 Pages) POWER

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LP6230A–01

Oct.-2013

Email: marketing@lowpowersemi.com

www.Lowpowersemi.com

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Preliminary Datasheet

LP6230A

Operation Information

The LP6230A uses a fixed frequency, peak current

mode boost regulator architecture to regulate

voltage at the feedback pin. At the start of each

oscillator cycle the MOSFET is turned on through

the control circuitry. To prevent sub-harmonic

oscillations at duty cycles greater than 50 percent,

a stabilizing ramp is added to the output of the

current sense amplifier and the result is fed into

the negative input of the PWM comparator. When

this voltage equals The output voltage of the error

amplifier the power MOSFET is turned off. The

voltage at the output of the error amplifier is an

amplified version of the difference between the

1.25V bandgap reference voltage and the

feedback voltage. In this way the peak current

level keeps the output in regulation. If the feedback

voltage starts to drop, the output of the error

amplifier increases. These results in more current

to flow through the power MOSFET, thus

increasing the power delivered to the output.

TheLP6230A has internal soft start to limit the

amount of input current at startup and to also limit

the amount of overshoot on the output.

Setting the Output Voltage

Set the output voltage by selecting the resistive

voltage divider ratio. The voltage divider drops the

output voltage to the 1.25V feedback voltage. Use

a 100K resistor for R2 of the voltage divider.

Determine the high-side resistor R1 by the

equation:

Vout=(R1/R2+1)×VFB

Vout=(R1/R2+1)×1.25V

Diode Selection

To achieve high efficiency, Schottky diode is good

choice for low forward drop voltage and fast

switching time. The output diode rating should be

able to handle the maximum output voltage, average

power dissipation and the pulsating diode peak

current.

Input Capacitor Selection

For better input bypassing, low-ESR ceramic

capacitors are recommended for performance. A

10μF input capacitor is sufficient for most

applications. For a lower output power requirement

application, this value can be decreased.

Layout Guideline

For high frequency switching power supplies, the

PCB layout is important step in system application

design. In order to let IC achieve good regulation,

high efficiency and stability, it is strongly

recommended the power components should be

placed as close as possible. The set races should be

wide and short. The feedback pin and then works of

feedback and compensation should keep away from

the power loops, and be shielded with a ground trace

or plane to prevent noise coupling.Input and Output

capacitors should be placed close to the IC and

connected to ground plane to reduce noise coupling.

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