Datasheet

LTC2978A
18
2978afa
For more information www.linear.com/LTC2978A
OPERATION
OPERATION OVERVIEW
The LTC2978A is a PMBus programmable power system
controller, monitor, sequencer and voltage supervisor that
can perform the following operations:
n
Accept PMBus compatible programming commands.
n
Provide DC/DC converter input voltage and output volt-
age/current read back through the PMBus interface.
n
Control the output of DC/DC converters that set the
output voltage with a trim pin or DC/DC converters
that set the output voltage using an external resistor
feedback network.
n
Sequence the start-up of DC/DC converters via PMBus
programming and their control input pins.
n
Trim the DC/DC converter output voltage (typically in
0.02% steps), in closed-loop servo operating mode,
through PMBus programming.
n
Margin the DC/DC converter output voltage to PMBus
programmed limits.
n
Allow the user to trim or margin the DC/DC converter
output voltage in a manual operating mode by providing
direct access to the margin DAC.
n
Supervise the DC/DC converter output voltage, input
voltage, and the LTC2978A die temperature for over-
value/undervalue conditions
with respect to PMBus
programmed limits and generate appropriate faults and
warnings.
n
Respond to a fault condition by either continuing op-
eration indefinitely, latching off after a programmable
deglitch
period or latching off immediately. A retry mode
may be used to automatically recover from a latched-off
condition.
n
Optionally stop trimming the DC/DC converter output
voltage after it reached the initial margin or nominal
target. Optionally allow servo to resume if target drifts
outside of V
OUT
warning limits.
n
Store command register contents with CRC to EEPROM
through PMBus programming.
n
Restore EEPROM contents through PMBus program-
ming or when V
DD33
is applied on power-up.
n
Report the DC/DC converter output voltage status
through the PMBus interface and the power good output.
n
Generate interrupt requests by asserting the ALERTB
pin in response to supported PMBus faults and
warnings.
n
Coordinate system wide fault responses for all DC/DC
converters connected to the FAULTBz0 and FAULTBz1
pins.
n
Synchronize sequencing delays or shutdown for multiple
devices using the SHARE_CLK pin.
n
Software and hardware write protect the command
registers.
n
Disable the input voltage to the supervised DC/DC
converters in response to output voltage OV and UV
faults.
n
Log telemetry and status data to EEPROM in response
to a faulted-off condition
n
Supervise an external microcontroller’s activity for a
stalled condition with a programmable watchdog timer
and reset it if necessary.
n
Prevent a DC/DC converter from re-entering the ON
state after a power cycle until a programmable interval
(MFR_RESTART_DELAY) has elapsed and its output
has decayed below a programmable threshold voltage
(MFR_VOUT_DISCHARGE_THRESHOLD).
n
Record minimum and maximum observed values of
input voltage, output voltages and temperature.
EEPROM
The LTC2978A contains internal EEPROM (nonvolatile
memory) to store configuration settings and fault log
information. EEPROM endurance, retention, and mass
write operation time are specified over the operating junc
-
tion temperature
range. See Electrical Characteristics and
Absolute Maximum Ratings sections.