Datasheet

LTC2924
10
2924fb
applicaTions inForMaTion
Up to five supplies can be sequenced to a sixth master
supply by a single LTC2924 (Figure 4). The turn on of the
first power supply is sensed by the ON pin. Power sup-
plies two through five are enabled by the OUT1 through
OUT4 pins, and their turn on sensed by the IN1 through
IN4 pins respectively. The last power supply is enabled by
the DONE pin, which is generally connected through an
in verter. This application is used where power supplies are
sequentially sequenced on and the turn off is simulta neous.
Multiple LTC2924s can be cascaded to facilitate sequenc-
ing of eight or more power supplies. See the Cascading
Multiple LTC2924s section.
Selecting the Hysteresis Current and IN Pin Feedback
Resistors
The IN1-IN4 pins are connected to a sequenced power
supply with a resistive divider. The resistors are calculated
by first selecting a hysteresis current, I
HYS
, and calculat-
ing R
HYS
:
R
HYS
=
0.5V
I
HYS
; 0.5µA ≤I
HYS
≤ 50µA
For each sequenced power supply, choose a voltage
when the power supply is considered to be On during
Figure 4. 6-Power Supply Sequencer Block Diagram
OUT1
OUT2
OUT3
OUT4
DONE
FAULT
ON
IN1
IN2
IN3
IN4
LTC2924
V
CC
GND
2924 F04
SHDN V
OUT
PS1
SHDN V
OUT
PS2
SHDN V
OUT
PS3
SHDN V
OUT
PS4
SHDN V
OUT
PS5
SHDN
*V
CC
EARLY MUST BE ON BEFORE
SEQUENCING SUPPLIES
V
OUT
PS6
TURN OFF
V
CC
EARLY*
SYSTEM
CONTROLLER