Case 1) Programmable Phase Delay.

Fig. 3 shows how to program a phase delay with a monostable multivibrator whose on time is equal to

the desired phase delay.

Case 2) Fixed Phase Delay.

Figure 3 shows a method of setting a delay time for the 2nd PWM section to be slightly larger than the

ON-time of the 1st PWM section.

Vcc

U1

L4973D3.3

GND

OSC

SYNC

Vref=5.1

C2

R1

U2

L4973D3.3

GND

OSC

SYNC

M74HC123

_

1Q

1A

GND

1B

Vcc

0

U1

t

0

U2

α

PWM OUTPUTS

Figure 3. Case 1) Programmable Phase Delay.

SYNC

Vref=5.1

Vout

L

Cout

OUT1

U1

L4973D3.3

OUT2

U2

L4973D3.3

Rs

Rs

L

Vcc

Vcc

Vcc

OSC

OSC

R1

C2

0

U1

t

0

U2

18V

*

PWM OUTPUTS

Figure 4. Case 2) Programmable Phase Delay.

AN1126 APPLICATION NOTE

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