LTC4311ISC6#PBF Linear Technology, LTC4311ISC6#PBF Datasheet - Page 9

• Manufacturer Part Number: LTC4311ISC6#PBF
• Manufacturer: Linear Technology

Specifications of LTC4311ISC6#PBF

• Lead Free Status / Rohs Status: Compliant

APPLICATIONS INFORMATION
This is the lowest resistor value that may be chosen and
still meet V
will satisfy SR, the minimum slew rate requirement. Us-
ing V
R
This is approximately the largest value of R
the minimum slew rate requirement. Since R
than 2.175k the V
will actually be faster than calculated. Choosing R
V
The rise and fall times need to be verifi ed using equations
3 and 4.
Both the rise and fall times meet the 0.3μs I
and the V
rate requirement, so R
If t
then R
OL
P
r
R
R
In
In
SR =
V
t
t
with equation 2.
r
is not met, R
f
and SR are recalculated.
OL
P
P
⎧
⎨
⎩
⎧
⎪
⎨
⎪
⎩
OL
= –10kΩ • 600pF •
= 291Ω • 600pF •
P
= 9.667k
0.99V – 3.3V – 10kΩ • 2.5mA
2.31V – 3.3V – 10kΩ • 2.5mA
0.99V
=
=
3.3V
3.3V
2.31
= 0.4V and SR = 0.5V/μs calculate the value of
10kΩ•600pF
should be increased.
3.3V – 96mV
600pF •0.5V / µs
OL
300Ω +10kΩ
300Ω•3.3V
OL
3.3V − 0.4V
is satisfi ed, while meeting the minimum slew
•(10kΩ + 300Ω) – 300Ω
. Next calculate the largest value of R
•(10kΩ + 300Ω) – 300Ω
P
OL
should be decreased and if t
will be below 0.4V, and the slew rate
P
= 0.534V / µs
= 96mV
is chosen to be 10k.
⎫
⎬
⎭
= 0.297µs
⎫
⎪
⎬
⎪
⎭
P
= 0.158µs
2
that will satisfy
C requirement
f
P
is not met
is larger
P
= 10k ,
P
(11)
(13)
(14)
(12)
that
SMBus Design Example
Given the following conditions and requirements for a low
power SMBus system:
If an R
200Ω, then R
to fi nd the required R
Calculate Maximum R
Choose R
The rise and fall times need to be verifi ed using equations
5 to 8.
C
R
R
R
R
ln
V
V
V
t
V
SR =
t
r
1
ILMAX
CC
OL
BUS
P
P
P
P
OL
⎧
⎨
⎩
= 1µs MAXIMUM,t
= –13kΩ • 400pF •
S
=
= 2.175k
=
= 14.5k
0.8V–0.15V–3.3V
= 3.3V NOMINAL
= 0.4V MAXIMUM
=
of 100Ω is used and the max R
300Ω•(3.3V – 0.4V)
= 400pF
13kΩ • 400pF
3.3V – 74mV
400pF •0.5V / µs
300Ω + 13kΩ
P
300Ω • 3.3V
0.9V–3.3V
= 0.8V,V
= 13k and recalculate V
3.3V – 0.4V
L
= 200Ω + 100Ω = 300Ω. Use equation 1
0.4V
IHMIN
P
P
to meet V
= 0.62V / µs
from equation 2.
f
= 74mV
= 2.1V
= 0.3µs MAXIMUM
⎫
⎬
⎭
= 0.515µs
OL
OL
.
and SR.
ON
LTC4311
of the driver is
(15)
(16)
(17)
(18)
(19)
4311fa
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