NCP3063 ONSEMI [ON Semiconductor], NCP3063 Datasheet - Page 7

• Manufacturer Part Number: NCP3063
• Description: 1.5 A, Step−Up/Down/Inverting Switching Regulators
• Manufacturer: ONSEMI [ON Semiconductor]

optimized for dc to dc converter applications. The
combination of its features enables the system designer to
directly implement step−up, step−down, and voltage−
inverting converters with a minimum number of external
components. Potential applications include cost sensitive
consumer products as well as equipment for industrial
markets. A representative block diagram is shown in
Figure 2.
Operating Description
gated oscillator to regulate output voltage. 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 shown is 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
The NCP3063 is a monolithic power switching regulator
The NCP3063 is a hysteric, dc−dc converter that uses a
Feedback Comparator Output
Nominal Output Voltage Level
I
PK
Comparator Output
Timing Capacitor, C
Output Switch
Output Voltage
On
Off
0
0
1
1
T
Figure 12. Typical Operating Waveforms
NCP3063, NCP3063B, NCV3063
Startup
http://onsemi.com
INTRODUCTION
7
controlled by the oscillator, thus pumping up the output filter
capacitor. When the output voltage level reaches nominal,
the output switch next cycle turning on is inhibited. The
feedback comparator will enable the switching immediately
when the load current causes the output voltage to fall below
nominal. Under these conditions, 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. (See AN920/D for more information).
Oscillator
are programmed by the value selected for timing capacitor
C
internal current source and sink, generating a positive going
sawtooth waveform at Pin 3. The oscillator peak and valley
voltage difference is 500 mV typically. To calculate the C
capacitor value for required oscillator frequency, use the
equations found in Figure 13. An Excel based design tool
can be found at www.onsemi.com on the NCP3063 product
page.
T
The oscillator frequency and off−time of the output switch
. Capacitor C
T
is charged and discharged by a 1 to 6 ratio
Operation
T