LTC1694-1IS5#PBF Linear Technology, LTC1694-1IS5#PBF Datasheet - Page 7

• Manufacturer Part Number: LTC1694-1IS5#PBF
• Manufacturer: Linear Technology

Specifications of LTC1694-1IS5#PBF

• Operating Temperature (min): -40C
• Operating Temperature Classification: Industrial
• Operating Temperature (max): 85C
• Rad Hardened: No
• Lead Free Status / Rohs Status: Compliant

Using equations 4 and 5 to check exact value of t
Using equation 7 to check t
which is less than 0.3 s.
Using equation 1 to check V
which is less than 0.4V.
And using equation 2 to check the initial slew rate:
which is greater than 0.5V/ s.
Therefore, the value of R
ACK Data Setup Time
Care must be taken in selecting the value of R
with the pull-down driver) to ensure that the data setup
time requirement for ACK (acknowledge) is fulfilled. An
acknowledge is accomplished by the SMBus host releas-
ing the SDA line (pulling high) at the end of the last bit sent
and the SMBus slave device pulling the SDA line low
before the rising edge of the ACK clock pulse.
APPLICATIONS
t
t
V
SR = 3.3/[(27 • 10
r
f
OL
= 0.535 s + 0.254 s = 0.79 s
= 0.222 s
= (3.3 • 700)/[700 + (27 • 10
SMBus
U
3
) • (200 • 10
SDA
SCL
P
INFORMATION
U
chosen is 27k.
Figure 3. Paralleling Two LTC1694-1 to Provide 4.4mA of Pull-Up Current
f
:
OL
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
:
5
4
–12
OUT
CLK
CLK
DEVICE 1
W
SMBus1
SMBus2
3
IN
)] = 83mV
LTC1694-1
)] = 0.61V/ s
GND
V
CC
S
U
(in series
1
2
V
r
5V
CC
DATA
DATA
:
OUT
IN
C1
0.1 F
The LTC1694-1 2.2mA pull-up current is activated when
the SMBus host releases the SDA line, allowing the
voltage to rise above the LTC1694-1’s comparator thresh-
old of 0.65V. If an SMBus slave device has a high value
of R
device to pull SDA low before the rising edge of the ACK
clock pulse.
To ensure sufficient data setup time for ACK, SMBus slave
devices with high values of R
earlier. Typically, a minimum setup time of 1.5 s is needed
for an SMBus device with an R
capacitance of 200pF.
An alternative is that the SMBus slave device can hold SCL
line low until the SDA line reaches a stable state. Then, SCL
can be released to generate the ACK clock pulse.
Connecting Multiple LTC1694-1 in Parallel
The LTC1694-1 is designed to guarantee a maximum
SMBus rise time of 1 s with a bus capacitance of 200pF.
In some cases where the bus capacitance is higher than
200pF, multiple LTC1694-1s can be connected in parallel
to provide a higher pull-up current to meet the rise time
requirement. Figure 3 shows a typical application with two
LTC1694-1s connected in parallel to supply a pull-up
current of 4.4mA.
1
2
V
GND
CC
LTC1694-1
S
, a longer time is required for this SMBus slave
SMBus1
SMBus2
OUT
CLK
CLK
DEVICE N
IN
5
4
DATA
DATA
OUT
IN
S
, should pull the SDA low
R
P1
S
1694-1 f03
of 700
R
P2
LTC1694-1
and a bus
16941fa
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