Timing-Off Sequence/Ramp - Analog Devices LTM4683 Manual

LTM4683
PMBus COMMAND DETAILS
TON_MAX_FAULT_LIMIT
The TON_MAX_FAULT_LIMIT command sets the value, in milliseconds, on how long the unit can attempt to power
up the output without reaching the output undervoltage fault limit.
A data value of 0ms means there is no limit, and the unit can attempt to bring up the output voltage indefinitely. The
maximum limit is 83 seconds.
This command has two data bytes and is formatted in Linear_5s_11s format.
VOUT_TRANSITION_RATE
When a PMBus device receives either a VOUT_COMMAND or OPERATION (Margin High, Margin Low) that causes the
output voltage to change, this command sets the rate in V/ms at which the output voltage changes. The commanded
rate of change does not apply when the unit is commanded On or Off. The maximum allowed slope is 4V/ms.
This command has two data bytes and is formatted in Linear_5s_11s format.
Timing—Off Sequence/Ramp
CMD
COMMAND NAME CODE DESCRIPTION
TOFF_DELAY 0x64 Time from RUN and/or Operation off to the
TOFF_FALL 0x65 Time from when the output starts to fall until
TOFF_MAX_WARN_LIMIT 0x66 Maximum allowed time, after TOFF_FALL
TOFF_DELAY
The TOFF_DELAY command sets the time, in milliseconds, from when a stop condition is received until the output
voltage starts to fall. Values from 0 to 83 seconds are valid. The resulting turn-off delay will have a typical delay of
270µs for TOFF_DELAY = 0 and an uncertainty of ±50µs for all values of TOFF_DELAY. TOFF_DELAY is not applied
when a fault event occurs.
This command has two data bytes and is formatted in Linear_5s_11s format.
TOFF_FALL
The TOFF_FALL command sets the time, in milliseconds, from the end of the turn-off delay time until the output volt-
age is commanded to zero. It is the ramp time of the V
set to a high impedance state.
The part will maintain the mode of operation programmed. For defined TOFF_FALL times, the user should set the part
to continuous conduction mode. Loading the max value indicates that the part will ramp down at the slowest pos-
sible rate. The minimum supported fall time is 0.25ms. A value less than 0.25ms will result in a 0.25ms ramp. The
maximum fall time is 1.3 seconds. The number of steps in TOFF_FALL is equal to TOFF_FALL (in ms)/0.1ms with an
uncertainty of ±0.1ms.
In discontinuous conduction mode, the controller will not draw current from the load, and the fall time will be set by
the output capacitance and load current.
This command has two data bytes and is formatted in Linear_5s_11s format.
100
start of TOFF_FALL ramp.
the output reaches zero volts.
completed, for the unit to decay below 12.5%.
For more information
TYPE PAGED
R/W Word Y
R/W Word Y
R/W Word Y
DAC. When the V
OUT OUT
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DATA
FORMAT UNITS NVM
L11 ms Y
L11 ms Y
L11 ms Y
DAC is zero, the PWM output will be
DEFAULT
VALUE
0.0
0x8000
3.0
0xC300
0
0x8000
Rev. 0