ISL85415

7. Application Guidelines

FN8373 Rev.5.01

Page 23 of 30

Jun.4.20

7.

Application Guidelines

7.1

Simplifying the Design

While the ISL85415 offers user programmed options for most parameters, the easiest implementation with fewest

components involves selecting internal settings for SS, COMP, and FS. Table 1 on page 3 provides component

value selections for a variety of output voltages that allow the designer to implement solutions with a minimum of

effort.

7.2

Operating Frequency

The ISL85415 operates at a default switching frequency of 500kHz if the FS pin is tied to VCC. Tie a resistor from

the FS pin to GND to program the switching frequency from 300kHz to 2MHz, as shown in Equation 4.

where t is the switching period in µs.

7.3

Synchronization Control

The frequency of operation can be synchronized up to 2MHz by an external signal applied to the SYNC pin. The

rising edge on the SYNC triggers the rising edge of PHASE. To properly sync, the external source must be at least

10% greater than the programmed free running IC frequency.

Figure 60. PWM Operation Waveforms

RFS k



108.75k

 t



0.2

s  1s



–

=

(EQ. 4)

300

200

100

0

500

750

1000

1250

1500

1750

2000

fSW (kHz)

400

250