Datasheet
LTC2924
13
2924fb
Cascading Multiple LTC2924s
Two or more LTC2924s may be cascaded to fully se quence
8,12 or more power supplies. Figures 7 and 8 show how
to configure the LTC2924 to sequence 8 and 12 power
supplies. To sequence more power supplies, use the
circuit in Figure 8 and add more LTC2924s in the middle.
Notice that the last LTC2924 in the cascade string must
have a pull-up resistor on the DONE pin. Any LTC2924
that is not the first in the cascade string should have the
hysteresis current setting resistor, R
HYS
, pulled to V
CC
instead of ground. The value of the R
HYS
resistor remains
unchanged. The FAULT pins should all be connected to-
gether and pulled up with a single 10k resistor.
Care should be taken when designing a circuit cascading
multiple LTC2924s. Use the following guidelines:
Figure 8. Cascading Three LTC2924s to Fully Sequence Up to 12 Power Supplies
• All V
CC
and ground pins for the LTC2924s in the cascade
chain must be connected to the same power supply.
• The ground pins should be connected via a ground
plane.
• Cascaded LTC2924s communicate using a combination
of levels and pulses which do not look like the normal
output of a DONE pin nor input to an ON pin. Do not
connect any other components to the node between
the DONE and ON pins. Keep the parasitic capacitance
on this node below 75pF. Care should be taken when
routing a circuit trace between DONE and ON. If pos-
sible, run the trace adjacent to the ground plane, and/
or shield the trace with a ground trace on either side.
Leakage currents must be maintained below 2µA on
this node.
applicaTions inForMaTion
Figure 7. Cascading Two LTC2924s to Fully Sequence Up to Eight Power Supplies
TMR
HYS/CFG
ON
IN1
IN2
IN3
IN4
V
CC
GND
PGT
OUT1
OUT2
OUT3
OUT4
DONE
LTC2924
V
CC
FAULT
V
CC
V
CC
DONE
10k
10k
FAULT
2924 F07
TMR
HYS/CFG
ON
IN1
IN2
IN3
IN4
V
CC
GND
PGT
OUT1
OUT2
OUT3
OUT4
DONE
LTC2924ON
R
HYS
R
HYS
FAULT
TMR
HYS/CFG
ON
IN1
IN2
IN3
IN4
V
CC
GND
PGT
OUT1
OUT2
OUT3
OUT4
DONE
LTC2924
V
CC
FAULT
V
CC
V
CC
DONE
10k
10k
FAULT
2924 F08
TMR
HYS/CFG
ON
IN1
IN2
IN3
IN4
V
CC
GND
PGT
OUT1
OUT2
OUT3
OUT4
DONE
LTC2924
R
HYS
R
HYS
FAULT
TMR
HYS/CFG
ON
IN1
IN2
IN3
IN4
V
CC
GND
PGT
OUT1
OUT2
OUT3
OUT4
DONE
LTC2924ON
R
HYS
FAULT