LTC3883 Datasheet, PDF (62/112 Pages) Linear Technology – Single Phase Step-Down DC/DC Controller with Digital Power System Management

LTC3883/LTC3883-1
Applications Information
Figure 31. LTpowerPlay Screen Shot
PMBus
WRITE
CMD
DECODER
DATA
MUX
CALCULATIONS
S
PENDING
R
CMDS
WRITE COMMAND
DATA BUFFER
PAGE
0x00
•••
0x21
VOUT_COMMAND
•
••
MFR_RESET 0xFD
x1
INTERNAL
PROCESSOR
FETCH,
CONVERT
DATA
AND
EXECUTE
3883 F32
Figure 32. Write Command Data Processing
Command data buffering handles incoming PMBus writes
by storing the command data to the Write Command Data
Buffer and marking these commands for future process-
ing. The internal processor runs in parallel and handles
the sometimes slower task of fetching, converting and
executing commands marked for processing.
Some computationally intensive commands (e.g., timing
parameters, temperatures, voltages and currents) have
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internal processor execution times that may be long relative
to PMBus timing. If the part is busy processing a command,
and new command(s) arrive, execution may be delayed
or processed in a different order than received. The part
indicates when internal calculations are in process via bit 5
of MFR_COMMON (‘calculations not pending’). When the
part is busy calculating, bit 5 is cleared. When this bit is
set, the part is ready for another command. An example
polling loop is provided in Figure 33 which ensures that
commands are processed in order while simplifying error
handling routines.
// wait until bits 6, 5, and 4 of MFR_COMMON are all set
do
{
mfrCommonValue = PMBUS_READ_BYTE(0xEF);
partReady = (mfrCommonValue & 0x70) == 0x70;
}while(!partReady)
Figure 33. Example of a Command Write of VOUT_COMMAND
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