DS28CM00 Maxim, DS28CM00 Datasheet - Page 9

• Manufacturer Part Number: DS28CM00
• Description: The DS28CM00 is a low-cost, electronic registration number to provide an absolutely unique identity that can be determined with the industry standard I²C and SMBus&#8482 interface
• Manufacturer: Maxim

Figure 6. Application Schematic
For I²C systems, the rise time and fall time are measured from 30% to 70% of the pullup voltage. The maximum
bus capacitance C
maximum resistor value at any given capacitance C
capacitance of 400pF the maximum pullup resistor would be 885Ω.
Since a 885Ω pullup resistor, as would be required to meet the rise time specification and 400pF bus capacitance,
is lower than R
first calculating the minimum pullup resistor at any given operating voltage ("Minimum R
the respective bus capacitance that yields a rise time of 300ns.
Only for pullup voltages of 4V and lower can the maximum permissible bus capacitance of 400pF be maintained. A
reduced bus capacitance of 300pF is acceptable for the entire operating voltage range. The corresponding pullup
resistor value at the voltage is indicated by the "Minimum R
Figure 7. I²C Fast Speed Pullup Resistor Selection Chart
PACKAGE INFORMATION
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to
www.maxim-ic.com/DallasPackInfo
1200
1000
PMIN
800
600
400
200
0
B
at 5.25V, a different approach is necessary. The "Max. Load…" line in Figure 7 is generated by
1.5
is 400pF. The maximum rise time must not exceed 300ns. Assuming maximum rise time, the
V
CC
.)
2
GND
µC
V
CC
"Minimum Rp"
SDA
SCL
2.5
Pull-up Voltage
3
R
P
Max. Load at Min. Rp fast mode
9 of 9
B
is calculated as: R
3.5
P
" line.
R
P
SDA
SCL
DS28CM00
GND
V
DS28CM00: I²C/SMBus Silicon Serial Number
CC
4
PMAX
4.5
To additional
devices
= 300ns/(C
P
" line) and then calculating
5
B
*ln(7/3)). For a bus
600
500
400
300
200
100
0