ISL70001SRH

4

FN6947.1

May 23, 2011

12

SS

This pin is the soft-start input. Connect a ceramic capacitor from this pin to DGND to set the soft-start output

ramp time in accordance with Equation 1:

Where:

Soft-start time is adjustable from approximately 2ms to 200ms.

The range of the soft-start capacitor should be 82nF to 8.2µF, inclusive.

13, 14

DVDD

These pins are the bias supply inputs to the internal digital control circuitry. Connect these pins together at the

IC and locally filter them to DGND using a 1

Ω resistor and a 1µF ceramic capacitor. Locate both filter

components as close as possible to the IC.

15, 16

DGND

These pins are the digital ground associated with the internal digital control circuitry. Connect these pins

directly to the ground plane.

17, 18

AGND

These pins are the analog ground associated with the internal analog control circuitry. Connect these pins

directly to the ground plane.

19

AVDD

This pin is the bias supply input to the internal analog control circuitry. Locally filter this pin to AGND using a 1

Ω

resistor and a 1µF ceramic capacitor. Locate both filter components as close as possible to the IC.

20

REF

This pin is the internal reference voltage output. Bypass this pin to AGND with a 220nF ceramic capacitor

located as close as possible to the IC. The bypass capacitor is needed to mitigate SEE. No current (sourcing or

sinking) is available from this pin.

21

FB

This pin is the voltage feedback input to the internal error amplifier. Connect a resistor from FB to VOUT and

from FB to AGND to adjust the output voltage in accordance with Equation 2:

Where:

The top divider resistor must be 1k

Ω to mitigate SEE. Connect a 4.7nF ceramic capacitor across RT to mitigate SEE

and to improve stability margins.

22

EN

This pin is the enable input to the IC. This is a comparator type input with a rising threshold of 0.6V and

programmable hysteresis. Driving this pin above 0.6V enables the IC. Bypass this pin to AGND with a 10nF

ceramic capacitor to mitigate SEE.

23

PORSEL

This pin is the input for selecting the rising and falling POR (Power-On-Reset) thresholds. For a nominal 5V

supply, connect this pin to DVDD. For a nominal 3.3V supply, connect this pin to DGND. For nominal supply

voltages between 5V and 3.3V, connect this pin to DGND.

PIN NUMBER

PIN NAME

DESCRIPTION

⋅

⁄

=

(EQ. 1)

⁄

()

+

[]

⋅

=

(EQ. 2)