DS2482S-800 Maxim Integrated Products, Inc., DS2482S-800 Datasheet - Page 21

• Manufacturer Part Number: DS2482S-800
• Description: Eight-channel 1-wire Master
• Manufacturer: Maxim Integrated Products, Inc.

Case C: 1-Wire busy (1WB = 1)
The master should stop and restart as soon as the DS2482 does not acknowledge the command code.
Figure 11. Application Schematic
Application Information
SDA and SCL Pullup Resistors
SDA is an open-drain output on the DS2482 that requires a pullup resistor to realize high logic levels. Because the
DS2482 uses SCL only as input (no clock stretching) the master can drive SCL either through an open-
drain/collector output with a pullup resistor or a push-pull output.
Pullup Resistor R
According to the I²C specification, a slave device must be able to sink at least 3mA at a V
condition determines the minimum value of the pullup resistor: Rpmin = (V
voltage of 5.5V, the minimum value for the pullup resistor is 1.7kW. The "Minimum RP" line in Figure 12 shows how
the minimum pullup resistor changes with the operating voltage.
For I²C systems, the rise time and fall time are measured from 30% to 70% of the pullup voltage. The maximum
bus capacitance C
fast speed. Assuming maximum rise time, the maximum resistor value at any given capacitance C
as: Rpmaxs = 1000ns/(C
S
AD,0
µC
P
(I²C port)
B
Sizing
is 400pF. The maximum rise time at standard speed must not exceed 1000ns and 300ns at
A
B
*ln(7/3)) (standard speed) and Rpmaxf = 300ns/(C
1WT
V
CC
*R
P
A\
SDA
SCL
AD0
AD1
AD2
SDA
SCL
AD0
AD1
AD2
DS2482-800
DS2482-800
P
V
CC
IO0
IO1
IO2
IO3
IO4
IO5
IO6
IO7
IO0
IO1
IO2
IO3
IO4
IO5
IO6
IO7
21 of 22
V
CC
*R
* R
*R
R
for R
t
t
t
P
Line termination resistor, typically 100W
I²C pull-up resistor, see Application Information
P
sizing.
1-Wire lines
CC
B
*ln(7/3)) (fast speed). For a bus
- 0.4V)/3mA. With an operating
1-Wire
Device #1
1-Wire
Device #2
OL
of 0.4V. This DC
b
is calculated