Datasheet

LM90
SNIS126A –MAY 2004–REVISED MARCH 2013 www.ti.com
SMBus DIGITAL SWITCHING CHARACTERISTICS
Unless otherwise noted, these specifications apply for V
DD
= +3.0 Vdc to +3.6 Vdc, C
L
(load capacitance) on output lines =
80 pF. Boldface limits apply for T
A
= T
J
= T
MIN
to T
MAX
; all other limits T
A
= T
J
= +25°C, unless otherwise noted.
The switching characteristics of the LM90 fully meet or exceed the published specifications of the SMBus version 2.0. The
following parameters are the timing relationships between SMBCLK and SMBData signals related to the LM90. They adhere
to but are not necessarily the SMBus bus specifications.
Typical
(1)
Limits
(2)
Units
Symbol Parameter Conditions
(Limit)
f
SMB
SMBus Clock Frequency 100 kHz (max)
10 kHz (min)
t
LOW
SMBus Clock Low Time from V
IN(0)
max to V
IN(0)
max 4.7 µs (min)
25 ms (max)
t
HIGH
SMBus Clock High Time from V
IN(1)
min to V
IN(1)
min 4.0 µs (min)
t
R,SMB
SMBus Rise Time See
(3)
1 µs (max)
t
F,SMB
SMBus Fall Time See
(4)
0.3 µs (max)
t
OF
Output Fall Time C
L
= 400pF, 250 ns (max)
I
O
= 3mA
(4)
t
TIMEOUT
SMBData and SMBCLK Time Low for Reset of 25 ms (min)
Serial Interface
(5)
35 ms (max)
t
SU;DAT
Data In Setup Time to SMBCLK High 250 ns (min)
t
HD;DAT
Data Out Stable after SMBCLK Low 300 ns (min)
900 ns (max)
t
HD;STA
Start Condition SMBData Low to SMBCLK Low 100 ns (min)
(Start condition hold before the first clock falling
edge)
t
SU;STO
Stop Condition SMBCLK High to SMBData Low 100 ns (min)
(Stop Condition Setup)
t
SU;STA
SMBus Repeated Start-Condition Setup Time, 0.6 µs (min)
SMBCLK High to SMBData Low
t
BUF
SMBus Free Time Between Stop and Start 1.3 µs (min)
Conditions
(1) Typicals are at T
A
= 25°C and represent most likely parametric norm.
(2) Limits are ensured to AOQL (Average Outgoing Quality Level).
(3) The output rise time is measured from (V
IN(0)
max + 0.15V) to (V
IN(1)
min − 0.15V).
(4) The output fall time is measured from (V
IN(1)
min - 0.15V) to (V
IN(1)
min + 0.15V).
(5) Holding the SMBData and/or SMBCLK lines Low for a time interval greater than t
TIMEOUT
will reset the LM90's SMBus state machine,
therefore setting SMBData and SMBCLK pins to a high impedance state.
SMBus Communication
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