NCP3066MN データシートの表示（PDF） - ON Semiconductor

部品番号

コンポーネント説明

メーカー

NCP3066MN

Up to 1.5 A Constant Current Switching Regulator for LEDs with ON/OFF Function

ON Semiconductor 

NCP3066, NCV3066

INTRODUCTION

The NCP3066 is a monolithic power switching regulator

optimized for LED Driver applications. Its flexible

architecture enables the system designer to directly

implement step−up, step−down, and voltage−inverting

converters with a minimum number of external components

for driving LEDs. A representative block diagram is shown

in Figure 3.

comparator value, the output switch cycle is inhibited. When

the load current causes the output voltage to fall below the

nominal value feedback comparator enables switching

immediately. Under these conditions, the output switch

conduction can be enabled for a partial oscillator cycle, a

partial cycle plus a complete cycle, multiple cycles, or a

partial cycle plus multiple cycles.

Operating Description

The NCP3066 operates as a fixed oscillator frequency

output voltage ripple gated regulator. In general, this mode

of operation is somewhat analogous to a capacitor charge

pump and does not require dominant pole loop

compensation for converter stability. The typical operating

waveforms are shown in Figure 12. The output voltage

waveform is shown for a step−down converter with the

ripple and phasing exaggerated for clarity. During initial

converter startup, the feedback comparator senses that the

output voltage level is below nominal. This causes the

output switch to turn on and off at a frequency and duty cycle

controlled by the oscillator, thus pumping up the output filter

capacitor. When the output voltage level reaches nominal

Oscillator

The oscillator frequency and off−time of the output switch

are programmed by the value of the timing capacitor CT. The

capacitor CT is charged and discharged by a 1 to 6 ratio

internal current source and sink, generating a positive going

sawtooth waveform at Pin 3. This ratio sets the maximum

tON/(tON + tOFF) of the switching converter as 6/(6+1) or

85.7% (typical). The oscillator peak and valley voltage

difference is 500 mV typically. To calculate the CT capacitor

value for required oscillator frequency, use the equations

found in Figure 15. An online NCP3066 design tool can be

found at www.onsemi.com, which aids in selecting

component values.

Figure 12. Typical Operating Waveforms

http://onsemi.com

7

Share Link: