6/12

Axelite Confidential Materials, do not copy or distribute without written consent.

Rev.1.0 Nov.21 2011

AX6618



FUNCTION PIN DESCRIPTIONS

FB

Connecting this pin to an external resistor divider receives the feedback voltage of

the regulator. The output voltage set by the resistor divider is determined by:

)

V

)(

2

R

1

R

+

1

(

×

5

.

0

=

V

OUT

Where R1 is connected from VOUT to FB with Kelvin sensing and R2 is connected

from FB to GND. A bypass capacitor may be connected with R1in parallel to improve load

transient response. The recommended R1 are in the range of 150K~220K.

VIN

Main supply input pins for power conversions. The voltage at this pin is monitored

for Power-On Reset purpose.

VCNTL

Power input pin of the control circuitry. Connecting this pin to a +5V (recommended)

supply voltage provides the bias for the control circuitry. The voltage at this pin is

monitored for Power-On Reset purpose.

POK

Power-OK signal output pin. This pin is an open-drain output used to indicate status

of output voltage by sensing FB voltage. This pin is pulled low when the rising FB voltage

is not above the VPOK threshold or the falling FB voltage is below the VPOK threshold,

indicating the output is not OK.

EN

Enable control pin. Pulling and holding this pin below 0.4V shuts down the output.

When re-enabled, the IC undergoes a new soft-start cycle. Left this pin open, this pin is

internal pulled up to VCNTL voltage, enabling the regulator.