ltc2978 Linear Technology Corporation, ltc2978 Datasheet - Page 52

• Manufacturer Part Number: ltc2978
• Description: Octal Pmbus Power Supply Monitor And Controller With Eeprom
• Manufacturer: Linear Technology Corporation

V
OV and UV warning threshold voltages are processed
by the LTC2978’s ADC. These thresholds are set by the
VOUT_OV_WARN_LIMIT and VOUT_UV_WARN_LIMIT
commands. If a warning occurs, the corresponding bits
are set in the status registers and the ALERTB output
is asserted low. Note that a warning will never cause a
VOUT_ENn output to disable a DC/DC converter.
Configuring the V
The V
diate bus voltage in the event of an output OV or UV
fault. Use the MFR_VINEN_OV_FAULT_RESPONSE and
MFR_VINEN_UV_FAULT_RESPONSE registers to config-
ure the V
fault conditions. The V
when the LTC2978 is commanded to re-enter the ON state
following a faulted-off condition.
A charge-pumped 5µA pull-up to 12V is also available
on the V
register description in the OPERATION section for more
information.
Figure 23 shows an application circuit where the V
output is used to trigger a SCR crowbar on the intermediate
bus in order to protect the DC/DC converter’s load from a
catastrophic fault such as a stuck top gate.
LTC2978
applicaTions inForMaTion

OUT
OV/UV Warnings
IN_EN
IN_EN
IN_EN
output may be used to disable the interme-
pin to assert low in response to VOUT_OV/UV
output. Refer to the MFR_CONFIG_ALL
IN_EN
IN_EN
Output
output will stop pulling low
IN_EN
Multichannel Fault Management
Multichannel fault management is handled using the
bidirectional FAULTBzn pins. The “z” designates the fault
zone which is either 0 or 1. There are two fault zones in
the LTC2978. Each zone contains 4-channels. Figure 13
illustrates the connections between channels and the
FAULTBzn pins.
• The MFR_FAULTBz0_PROPAGATE command acts like
• To establish dependencies across fault zones, tie the
• A FAULTBzn pin can also be asserted low by an external
a programmable switch that allows faulted-off condi-
tions from a particular channel (PAGE) to propagate
to either FAULTBzn output in that channel’s zone. The
MFR_FAULTBzn_RESPONSE command controls similar
switches on the inputs to each channel that allow any
channel to shut down in response to any combination of
the FAULTBzn pins within a zone. Channels responding
to a FAULTBzn pin pulling low will attempt a new start
sequence when the FAULTBzn pin in question is released
by the faulted channel.
fault pins together, e.g., FAULTB01 to FAULTB10. Any
channel can depend on any other. To disable all chan-
nels in response to any channel faulting off, short all
the FAULTBzn pins together, and set MFR_FAULTBzn_
PROPAGATE = ‘h01 and MFR_FAULTBzn_RESPONSE
= ‘h0F for all channels.
driver in order to initiate an immediate off-sequence
after a 10µs deglitch delay.
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