lm25066apsqx National Semiconductor Corporation, lm25066apsqx Datasheet - Page 45

• Manufacturer Part Number: lm25066apsqx
• Description: Lm25066a System Power Management And Protection Ic With Pmbus
• Manufacturer: National Semiconductor Corporation

SMBus Communications Timing
Requirements
Note 8: Devices participating in a transfer will timeout when any clock low exceeds the value of T
condition must reset the communication no later than T
the cumulative stretch limit for both a master (10ms) and a slave (25ms).
Note 9: T
Note 10: T
this time, it is expected to release both its clock and data lines and reset itself.
Note 11: T
to-ack, or ack-to-stop.
Note 12: Rise and fall time is defined as follows:
• T
• T
T
T
T
Symbol
T
T
T
T
T
LOW:MEXT
LOW:SEXT
TIMEOUT
T
T
F
SU:STO
HD:DAT
T
HD:STA
SU:STA
SU:DAT
R
F
HIGH
T
SMB
LOW
T
BUF
= 0.9 VDD to (V
= ( V
R
F
HIGH MAX
LOW:SEXT
LOW:MEXT
ILMAX
– 0.15) to (V
provides a simple method for devices to detect bus idle conditions.
Hold time after (Repeated) Start Condition. After this
is the cumulative time a slave device is allowed to extend the clock cycles in one message from the initial start to the stop. If a slave exceeds
is the cumulative time a master device is allowed to extend its clock cycles within each byte of a message as defined from start-to-ack, ack-
ILMAX
Bus free time between Stop and Start Condition
Cumulative clock low extend time (slave device)
Cumulative low extend time (master device)
– 0.15)
IHMIN
Repeated Start Condition setup time
period, the first clock is generated.
SMBus Operating Frequency
+ 0.15)
Stop Condition setup time
Clock or Data Rise Time
Clock or Data Fall Time
Clock low time-out
Clock high period
Clock low period
Data setup time
Data hold time
Parameter
TIMEOUT,MAX
TABLE 45. SMBus Timing Definition
FIGURE 19. SMBus Timing Diagram
of 35 ms. The maximum value must be adhered to by both a master and a slave as it incorporates
45
Min
300
100
1.3
0.6
0.6
0.6
1.5
0.6
10
25
20
20
TIMEOUT,MIN
Limits
of 25 ms. Devices that have detected a timeout
Max
400
300
300
35
25
10
Units
kHz
ms
ms
ms
µs
µs
µs
µs
ns
ns
µs
µs
ns
ns
301460a1
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