NCP1512

http://onsemi.com

7

Figure 3. PWM Circuit Schematic

-

+

-

+

C1

10

m

Latch

OC Detect

COMP

OVP

COMP

Error Amp

Q2

Q1

L1

6.8

mH

R3

R4

En Ramp

Set

R1

R2

Sync

Q

S

R

En

C2

10

m

LOAD

400 m

300 m

200 m

400 m

200 m

0.00

Figure 4. Waveforms During PWM Operation

3.6040

3.6000

3.5960

400 m

100 m

-200 m

3.01

3.00

2.99

3.70

2.00

-0.30

196.0

201.0

204.0

207.0

210.0

213.0

TIME (

m)

PWM Mode with Internal Oscillator

If a synchronization signal is not available, the converter

has a 1.0 MHz internal oscillator available. The Sync Pin

must be held high to enter this mode. The characteristics of

the PWM mode with internal oscillator are similar to the

Sync PWM Mode.

Pulsed Mode

During low-level current output, NCP1512 can enter a

low current consumption mode when the Sync Pin is held

low. This mode will typically have a free running frequency

and an output voltage ripple similar to a PFM mode. The

advantage of the Pulsed mode is much lower Iq (14

mA) and

drastically higher efficiency compared with PWM and

PFM modes in low output loads.