Datasheet

LTC2974
84
2974fc
For more information www.linear.com/LTC2974
applicaTions inForMaTion
Multi-Channel Fault Management
Multi-channel fault management is handled using the
bidirectional FAULTB pins. Figure 28 illustrates the con
-
nections between channels and the FAULTB pins.
• The MFR_FAULTBn_PROPAGATE register acts like a
programmable switch that allows faulted_off conditions
from a particular channel (PAGE) to propagate to either
FAULTB output. The MFR_FAULTBn_RESPONSE register
controls similar switches on the inputs to each channel
that allow any channel to shut down in response to any
combination of the FAULTB pins. Channels responding
to a FAULTB pin pulling low will attempt a new start
sequence when the FAULTB pin in question is released
by the faulted channel.
• A FAULTB 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 LTC2974’S
Figure 29 shows how to interconnect the pins in a typical
multi-LTC2974 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 LTC2974 based
on V
IN
and ignore the CONTROL line and the OPERATION
Figure 28. Channel Fault Management Block Diagram
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_LTC2974 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 AUXFAULTB 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 con
-
verters. The LTC2974 allows a rich combination of faults
and warnings to be propagated to the ALERTB pin.
•
WDI/RESETB can be used to put the LTC2974 in the
power-on reset state. Pull WDI/RESETB low for at least
t
RESETB
to enter this state.
• The FAULTB lines can be connected together to create
fault dependencies. Figure 29 shows a configuration
where a fault on any FAULTB will pull all others low.
This is useful for arrays where it is desired to abort
a startup sequence in the event any channel does not
come up (see Figure 30).
• PWRGD reflects the status of the outputs that are
mapped to it by the MFR_PWRGD_EN command. Fig
-
ure 29 shows all the PWRGD pins connected together,
but any combination may be used.
CHANNEL 0
EVENT PROCESSOR
PAGE = 0
Mfr_faultb0_response, page = 0
Mfr_faultb1_response, page = 0
Mfr_faultb0_propagate_chan0
FAULTB0
FAULTED_OFF
FAULTED_OFF
FAULTED_OFF
FAULTED_OFF
Mfr_faultb1_propagate_chan0
CHANNEL 1
EVENT PROCESSOR
PAGE = 1
Mfr_faultb0_response, page = 1
Mfr_faultb1_response, page = 1
Mfr_faultb0_propagate_chan1
Mfr_faultb1_propagate_chan1
CHANNEL 2
EVENT PROCESSOR
PAGE = 2
Mfr_faultb0_response, page = 2
Mfr_faultb1_response, page = 2
Mfr_faultb0_propagate_chan2
Mfr_faultb1_propagate_chan2
CHANNEL 3
EVENT PROCESSOR
PAGE = 3
Mfr_faultb0_response, page = 3
Mfr_faultb1_response, page = 3
Mfr_faultb0_propagate_chan3
Mfr_faultb1_propagate_chan3
FAULTB1
2974 F28