LM90

SNIS126A – MAY 2004 – REVISED MARCH 2013

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SMBus DIGITAL SWITCHING CHARACTERISTICS

Unless otherwise noted, these specifications apply for VDD= +3.0 Vdc to +3.6 Vdc, CL (load capacitance) on output lines =

80 pF. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = +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)

fSMB

SMBus Clock Frequency

100

kHz (max)

10

kHz (min)

tLOW

SMBus Clock Low Time

from VIN(0)max to VIN(0)max

4.7

µs (min)

25

ms (max)

tHIGH

SMBus Clock High Time

from VIN(1)min to VIN(1)min

4.0

µs (min)

tR,SMB

SMBus Rise Time

See (3)

1

µs (max)

tF,SMB

SMBus Fall Time

See (4)

0.3

µs (max)

tOF

Output Fall Time

CL = 400pF,

250

ns (max)

IO = 3mA

(4)

tTIMEOUT

SMBData and SMBCLK Time Low for Reset of

25

ms (min)

Serial Interface (5)

35

ms (max)

tSU;DAT

Data In Setup Time to SMBCLK High

250

ns (min)

tHD;DAT

Data Out Stable after SMBCLK Low

300

ns (min)

900

ns (max)

tHD;STA

Start Condition SMBData Low to SMBCLK Low

100

ns (min)

(Start condition hold before the first clock falling

edge)

tSU;STO

Stop Condition SMBCLK High to SMBData Low

100

ns (min)

(Stop Condition Setup)

tSU;STA

SMBus Repeated Start-Condition Setup Time,

0.6

µs (min)

SMBCLK High to SMBData Low

tBUF

SMBus Free Time Between Stop and Start

1.3

µs (min)

Conditions

(1)

Typicals are at TA = 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 (VIN(0)max + 0.15V) to (VIN(1)min − 0.15V).

(4)

The output fall time is measured from (VIN(1)min - 0.15V) to (VIN(1)min + 0.15V).

(5)

Holding the SMBData and/or SMBCLK lines Low for a time interval greater than tTIMEOUT will reset the LM90's SMBus state machine,

therefore setting SMBData and SMBCLK pins to a high impedance state.

SMBus Communication

6

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