Datasheet

LTC2977
16
2977fa
For more information www.linear.com/LTC2977
OPERATION
OPERATION OVERVIEW
The LTC2977 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 readback 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. Time-based
sequencing and tracking sequencing are both supported.
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 LTC2977 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
operation indefinitely, latching off after a programmable
deglitch period, latching off immediately or sequencing
off after TOFF_DELAY. A retry mode may be used to
automatically recover from a latched-off condition.
When enabled, the number of retries (0 to 6 or infinite)
is the same for all pages and is programmed in MFR_
RETRY_COUNT.
n
Optionally stop trimming the DC/DC converter output
voltage after reaching 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.
n
Access user EEPROM data directly, without altering
RAM space (MFR_EE_UNLOCK, MFR_EE_ERASE, and
MFR_EE_DATA). Facilitates in-house bulk programming.