IR3087PBF

DESIGN PROCEDURES - IR3081A AND IR3087 CHIPSET

IR3081A EXTERNAL COMPONENTS

Oscillator Resistor Rosc

The oscillator of IR3081A generates a triangle waveform to synchronize the phase ICs, and the switching frequency

the curve in Figure 13.

over-current latch delay time, and power good delay time, they should be considered together while choosing

The SS/DEL pin voltage controls the slew rate of the converter output voltage, as shown in Figure 10. After the

ENABLE pin voltage rises above 0.6V, there is a soft-start delay time

released to allow the soft start. The soft start time

O

SS

O

SS

CHG

DEL

SS

V

t

V

t

I

C

*

10

*

70

*

6

/

−

=

=

(1)

delay time

and (4) respectively.

6

/

/

10

*

70

3

.

1

*

3

.

1

*

−

=

=

DEL

SS

CHG

DEL

SS

SSDEL

C

I

C

t

(2)

6

/

/

10

*

40

115

.

0

*

115

.

0

*

−

=

=

DEL

SS

OCDISCHG

DEL

SS

OCDEL

C

I

C

t

(3)

6

/

/

10

*

70

)

3

.

1

735

.

3

(

*

)

3

.

1

065

.

0

8

.

3

(

*

−

−

−

=

−

−

−

=

O

DEL

SS

CHG

O

DEL

SS

VccPG

V

C

I

V

C

t

(4)

shown in Figure15.

DOWN

SINK

VDAC

SR

I

C

=

(5)

2

15

10

2

.

3

5

.

0

VDAC

VDAC

C

R

−

∗

+

=

(6)

VDAC

SOURCE

UP

C

I

SR

=

(7)

Page 15 of 35