LTC2924

12

2924fa

Cascading Multiple LTC2924s

Two or more LTC2924s may be cascaded to fully sequence

8,12 or more power supplies. Figures 7 and 8 show how

to configure the LTC2924 to sequence 8 and 12 power

supplies.Tosequencemorepowersupplies,usethecircuit

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 DONE pin. Any LTC2924

that is not the first in the cascade string should have the

unchanged. The FAULT 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

Figure 7. Cascading Two LTC2924s to Fully Sequence Up to Eight Power Supplies

APPLICATIO S I FOR ATIO

TMR

HYS/CFG

ON

IN1

IN2

IN3

IN4

GND

PGT

OUT1

OUT2

OUT3

OUT4

DONE

LTC2924

FAULT

DONE

10k

10k

FAULT

2924 F07

TMR

HYS/CFG

ON

IN1

IN2

IN3

IN4

GND

PGT

OUT1

OUT2

OUT3

OUT4

DONE

LTC2924

ON

FAULT

TMR

HYS/CFG

ON

IN1

IN2

IN3

IN4

GND

PGT

OUT1

OUT2

OUT3

OUT4

DONE

LTC2924

FAULT

DONE

10k

10k

FAULT

2924 F08

TMR

HYS/CFG

ON

IN1

IN2

IN3

IN4

GND

PGT

OUT1

OUT2

OUT3

OUT4

DONE

LTC2924

FAULT

TMR

HYS/CFG

ON

IN1

IN2

IN3

IN4

GND

PGT

OUT1

OUT2

OUT3

OUT4

DONE

LTC2924

ON

FAULT

chain must be connected to the same power supply.

• The ground pins should be connected via a ground

plane.

• CascadedLTC2924scommunicateusingacombination

of levels and pulses which do not look like the normal

output of a DONE pin nor input to an ON pin. Do not

connect any other components to the node between

the DONE and ON pins. Keep the parasitic capacitance

on this node below 75pF. Care should be taken when

routing a circuit trace between DONE 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.