Datasheet

LTC2978A
69
2978afa
For more information www.linear.com/LTC2978A
Figure 20. Typical Connections Between Multiple LTC2978As
VIN_SNS
VIN_EN
SDA
SCL
ALERTB
CONTROL0
CONTROL1
WDI/RESETB
FAULTB00
FAULTB01
FAULTB10
FAULTB11
SHARE_CLK
PWRGD
GND
LTC2978A N-1
VIN_SNS
VIN_EN
SDA
SCL
ALERTB
CONTROL0
CONTROL1
WDI/RESETB
FAULTB00
FAULTB01
FAULTB10
FAULTB11
SHARE_CLK
PWRGD
GND
2978a F20
LTC2978A N
TO V
IN
OF
DC/DCs
TO INPUT
SWITCH
TO HOST CONTROLLER
TO OTHER LTC2978As–10k EQUIV PULL-UP RECOMMENDED
ON EACH LINE EXCEPT SHARE_CLK (USE 5.49k)
APPLICATIONS INFORMATION
• A FAULTBzn pin can also be asserted low by an external
driver in order to initiate an immediate off-sequence
after a 10µs deglitch delay.
INTERCONNECT BETWEEN MULTIPLE LTC2978A’S
Figure 20 shows how to interconnect the pins in a typical
multi-LTC2978A array.
• All V
IN_SNS
lines should be tied together in a star type
connection at the point where V
IN
is to be sensed.
This will minimize timing errors for the case where the
ON_OFF_CONFIG is configured to start the LTC2978A
based on V
IN
and ignore the CONTROL line and the
OPERATION command. In multi-part applications that
are sensitive to timing differences, it is recommended
that the Vin_share_enable bit of the MFR_CONFIG_
ALL_LTC2978 register be set high in order to allow
SHARE_CLK to synchronize on/off sequencing in
response to the VIN_ON and VIN_OFF thresholds.
• Connecting all V
IN_EN
lines together will allow selected
faults on any DC/DC converter’s output in the array to
shut off a common input switch.
• ALERTB is typically one line in an array of PMBus
converters. The LTC2978A allows a rich combination
of
faults and warnings to be propagated to the ALERTB
pin.
•
WDI/RESETB can be used to put the LTC2978A in the
power-on reset state. Pull WDI/RESETB low for at least
t
RESETB
to enter this state.
• The FAULTBzn lines can be connected together to create
fault dependencies. Figure 20 shows a configuration
where a fault on any FAULTBzn will pull all others low.
This is useful for arrays where it is desired to abort a
start-up sequence in the event any channel does not
come up (see Figure 21).