2

FN6413.0

December 21, 2006

FIGURE 1. TYPICAL ISL8723 APPLICATION USAGE

AOUT

AIN

BIN

CIN

DIN

BOUT

COUT

DOUT

UVLO_B

UVLO_A

UVLO_D

UVLO_C

ENABLE

SYSRST#

GROUND

RESET#

VDD

Pin Descriptions

PIN

#

PIN NAME

FUNCTION

DESCRIPTION

23

VDD

Chip Bias

Bias IC from nominal 2.5V to 5V

10

GND

Bias Return

IC ground

1

ENABLE/

ENABLE#

Input to start on/off

sequencing.

Input to initiate the start of the programmed sequencing of supplies on or off. Enable functionality is

disabled for 10ms after UVLO is satisfied. ISL8723 has ENABLE. ISL8724 has ENABLE#.

24

RESET#

RESET# Output

RESET# provides a high signal ~160ms after all GATEs are fully enhanced. This delay is for stabilization

of output voltages. RESET# will assert low upon any UVLO not being satisfied or ENABLE/ENABLE#

being deasserted. The RESET# output is an open drain N-channel FET and is guaranteed to be in the

correct state for VDD down to 1V and is filtered to ignore fast transients on VDD and UVLO_X.

20

UVLO_A

Under Voltage Lock

Out/Monitoring

Input

These inputs provide for a programmable UV lockout referenced to an internal 0.631V reference and

are filtered to ignore short (<7µs) transients below programmed UVLO level.

12

UVLO_B

17

UVLO_C

14

UVLO_D

21

DLY_ON_A

Gate On Delay

Timer Output

cap is charged with 1µA, 10ms after turn-on initiated by ENABLE/ENABLE# with an internal current

source providing delayed enhancement of the associated FETs GATE to turn-on.

8DLY_ON_B

16

DLY_ON_C

15

DLY_ON_D

18

DLY_OFF_A

Gate Off Delay

Timer Output

capacitor to ground. Each cap is charged with a 1µA internal current source to an internal reference

voltage causing the corresponding gate to be pulled down thus turning-off the FET.

13

DLY_OFF_B

3

DLY_OFF_C

4

DLY_OFF_D

2

GATE_A

FET Gate Drive

Output

Drives the external FETs with a 10µA current source to soft start ramp into the load. During sequence

off, 10µA is sunk from this pin to control the FET turn-off. During a turn-off due to a fault, the gate will

sink ~75mA to ensure a rapid turn-off.

5GATE_B

6GATE_C

7GATE_D

ISL8723, ISL8724