7

LTC1694-1

LTC1694-1

GND

5V

C1

0.1

µF

SMBus1

SMBus2

1

2

5

4

LTC1694-1

GND

SMBus1

SMBus2

5

4

1

2

SCL

SDA

DEVICE 1

CLK

IN

CLK

OUT

SMBus

DATA

IN

DATA

OUT

DEVICE N

1694-1 f03

CLK

IN

CLK

OUT

DATA

IN

DATA

OUT

Figure 3. Paralleling Two LTC1694-1 to Provide 4.4mA of Pull-Up Current

which is less than 0.3

µs.

which is less than 0.4V.

And using equation 2 to check the initial slew rate:

µs

which is greater than 0.5V/

µs.

ACK Data Setup Time

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.

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

device to pull SDA low before the rising edge of the ACK

clock pulse.

To ensure sufficient data setup time for ACK, SMBus slave

earlier. Typically, a minimum setup time of 1.5

µsisneeded

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

µs 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.

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.