SNIU028D February 2016 – September 2020 UCD3138 , UCD3138064 , UCD3138064A , UCD3138128 , UCD3138A , UCD3138A64
These diagrams give the low level timing for the PMBus logic. They show the timing between events on the PMBus pins and PMBus register changes.
For each timing parameter, only one case is shown. Note that the same timing parameter may occur in different places in a PMBus message.
Some of the timing diagrams show a clock stretch. These are optional. If the firmware can respond fast enough, no clock stretch will be necessary.
Note: Stretch is optional, depending on firmware timing.
Note: Stretch is optional, depending on firmware timing.
Parameter | Min | Max | Units |
---|---|---|---|
tSTART – Time from PMBUS_DATA low for Start signal to UNIT_BUSY bit set | 366 | 470 | ns |
tSAR – Time from PMBUS_CLK low on bit 8 to SLAVE_ADDR_READY bit set | 488 | 605 | ns |
tDREQ1 – Time from PMBUS_CLK low on bit 8 of address byte to DATA_REQUEST bit set | 427 | 538 | ns |
tACKWRITE – Time from write to ACK bit until UCD releases clock stretch | 427 | 538 | ns |
tDREQ2 – Time from write to ACK bit until DATA_REQUEST bit is set | ns | ||
tRPTSTRT – Time from PMBUS_DATA low for Repeated Start to RPT_START bit set | 366 | 470 | ns |
tDREQ3 – Time from PMBUS_CLK low on bit 8 of read byte to DATA_REQUEST bit set | 427 | 538 | ns |
tTXBWRITE – Time from PMBUS_CLK low on bit 8 to SLAVE_ADDR_READY bit set | 427 | 538 | ns |
tDRDY – Time from PMBUS_CLK low on bit 8 to DATA_RDY bit set | 488 | 605 | ns |
tEOM – Time from PMBUS_CLK high for Stop signal to EOM and DATA_RDY bits set, as well as PEC VALID and RD_BYTE_COUNT loaded with correct value. | 427 | 538 | ns |
PMBus/I2C edge which triggers change | Bit Field Changed | Min(ns) | Max(ns) |
---|---|---|---|
SCL rise or fall | SCL_RAW set or clear | 244 | 336 |
SDA rise or fall | SDA_RAW set or clear | 244 | 336 |
CONTROL rise or fall | CONTROL_RAW set or clear | 244 | 336 |
ALERT rise or fall | ALERT_RAW set or clear | 244 | 336 |
CONTROL edge specified by CNTL_INT_EDGE | CONTROL_EDGE | 244 | 336 |
ALERT falling edge | ALERT_EDGE | 244 | 336 |
SCL and SDA high for nominal 50 usec | BUS_FREE set | 122 | 202 |
Interval | Min(ns) | Max(ns) |
---|---|---|
PMBST Bit Set to Interrupt Trigger | 61 | 67 |