ISL85415

5. Detailed Description

FN8373 Rev.5.01

Page 21 of 30

Jun.4.20

approximately 300mA and are issued at a frequency equal to the converters programmed PWM operating

frequency.

Due to the pulsed current nature of PFM mode, the converter can supply limited current to the load. If the load

current rises beyond the limit, VOUT begins to decline. A second comparator signals an FB voltage 2% lower than

the 600mV reference and forces the converter to return to PWM operation.

5.6

Output Voltage Selection

The regulator output voltage is easily programmed using an external resistor divider to scale VOUT relative to the

internal reference voltage. The scaled voltage is applied to the inverting input of the error amplifier; see Figure 59.

The output voltage programming resistor, R3, depends on the value chosen for the feedback resistor, R2, and the

desired output voltage, VOUT, of the regulator. Equation 3 describes the relationship between VOUT and resistor

values.

If the desired output voltage is 0.6V, then R3 is left unpopulated and R2 is 0Ω.

Figure 59. External Resistor Divider

R2

R3

0.6V

EA

Reference

VOUT

FB

R3

R2 0.6V



VOUT 0.6V

–

---------------------------------

=

(EQ. 3)