Datasheet

LTC2974
16
2974fc
For more information www.linear.com/LTC2974
operaTion
LTC2974 OPERATION OVERVIEW
The LTC2974 is a PMBus programmable power supply
controller, monitor, sequencer and voltage and current
supervisor that can perform the following operations:
• Accept PMBus compatible programming commands.
• Provide DC/DC converter input voltage, output voltage,
output current, output temperature, and internal junction
temperature readback through the PMBus interface.
• 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.
• Sequence the startup of DC/DC converters via PMBus
programming and the CONTROL input pins. The LTC
2974 supports time-based sequencing and tracking
sequencing. Cascade sequence on with time based
sequence off is also supported.
• Trim the DC/DC converter output voltage (typically in
0.02% steps), in closed-loop servo operating mode,
autonomously or through PMBus programming.
• Margin the DC/DC converter output voltage to PMBus
programmed limits.
• Trim or margin the DC/DC converter output voltage with
direct access to the margin DAC.
• Supervise the DC/DC converter input voltage, output
voltage, load current and the inductor temperatures
for overvalue/undervalue conditions with respect to
PMBus programmed limits and generate appropriate
faults and warnings.
• Accurately handle inductor self-heating transients using
a proprietary algorithm. These self-heating effects are
combined with external temperature sensor readings
to improve accuracy of current supervisors and ADC
current measurement.
• Respond to a fault condition by continuing operation
indefinitely, latching-off after a programmable deglitch
period, latching-off immediately or sequencing off
after TOFF_DELAY. Use retry mode to automatically
recover from a latched-off condition. With retry enabled,
MFR_RETRY_COUNT programs the number of retries
(0 to 6 or infinite) for all pages.
• Optionally stop trimming the DC/DC converter output
voltage after it reaches the initial margin or nominal
target. Optionally allow servo to resume if target drifts
outside of V
OUT
warning limits.
• Store command register contents with CRC to EEPROM
through PMBus programming.
• Restore EEPROM contents through PMBus program
-
ming or when VDD33 is applied on power-up.
• Report the DC/DC converter output voltage status
through the power good output.
• Generate interrupt requests by asserting the ALERTB pin
in response to supported PMBus faults and warnings.
• Coordinate system wide fault responses for all DC/DC
converters connected to the LTC2974 FAULTB0 and
FAULTB1 pins.
• Synchronize sequencing delays or shutdown for multiple
devices using the SHARE_CLK pin.
• Software and hardware write protect the command
registers.
• Disable the input voltage to the supervised DC/DC
converters in response to output OV, UV, OC and UC
faults.
• Log telemetry and status data to EEPROM in response
to a faulted-off condition.
• Supervise an external microcontroller’s activity for a
stalled condition with a programmable watchdog timer
and reset it if necessary.
• 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).
• Record minimum and maximum observed values of
input voltage, output voltages, output currents and
output temperatures.
• Access user EEPROM data directly, without alter
-
ing RAM space (Mfr_ee_unlock, Mfr_ee_erase, and
Mfr_ee_data).
Facilitates
in-house
bulk
programming.