Datasheet
SCL
V
IH
V
IL
V
IH
V
IL
P S
S P
SDA
t
HD;DAT
t
SU;STO
t
HD;STA
t
SU;STA
t
SU;DAT
t
HIGH
t
BUF
t
LOW
t
R t
F
LM5066
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SNVS655G –JUNE 2011–REVISED FEBRUARY 2013
SMBUS COMMUNICATIONS TIMING REQUIREMENTS
Figure 19. SMBus Timing Diagram
Table 45. SMBus Timing Definition
Limits
Symbol Parameter Units Comments
Min Max
F
SMB
SMBus Operating Frequency 10 400 kHz
T
BUF
Bus free time between Stop and Start Condition 1.3 µs
T
HD:STA
Hold time after (Repeated) Start Condition. After this 0.6 µs
period, the first clock is generated.
T
SU:STA
Repeated Start Condition setup time 0.6 µs
T
SU:STO
Stop Condition setup time 0.6 µs
T
HD:DAT
Data hold time 85 ns
T
SU:DAT
Data setup time 100 ns
T
TIMEOUT
Clock low time-out 25 35 ms
(1)
T
LOW
Clock low period 1.5 µs
T
HIGH
Clock high period 0.6 µs
(2)
T
LOW:SEXT
Cumulative clock low extend time (slave device) 25 ms
(3)
T
LOW:MEXT
Cumulative low extend time (master device) 10 ms
(4)
T
F
Clock or Data Fall Time 20 300 ns
(5)
T
R
Clock or Data Rise Time 20 300 ns
(5)
(1) Devices participating in a transfer will timeout when any clock low exceeds the value of T
TIMEOUT,MIN
of 25 ms. Devices that have
detected a timeout condition must reset the communication no later than T
TIMEOUT,MAX
of 35 ms. The maximum value must be adhered
to by both a master and a slave as it incorporates the cumulative stretch limit for both a master (10ms) and a slave (25ms).
(2) T
HIGH MAX
provides a simple method for devices to detect bus idle conditions.
(3) T
LOW:SEXT
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 this time, it is expected to release both its clock and data lines and reset itself.
(4) T
LOW:MEXT
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-to-ack, or ack-to-stop.
(5) Rise and fall time is defined as follows:• T
R
= ( V
ILMAX
– 0.15) to (V
IHMIN
+ 0.15)• T
F
= 0.9 VDD to (V
ILMAX
– 0.15)
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