p82b715t NXP Semiconductors, p82b715t Datasheet - Page 6

• Manufacturer Part Number: p82b715t
• Description: I2c Bus Extender
• Manufacturer: NXP Semiconductors

Philips Semiconductors
The capacitance figures for one or more individual I
should be multiplied by a factor of 10 times, and then added to the
Buffered bus capacitance. Calculation of a new Buffered bus pull-up
resistor will alllow this single pull-up resistor to act for both the
included I
combine some or all of these separate pull-up resistors into a single
resistor on the Buffered bus (the value of which is calculated from
the sum of the scaled capacitances on the Buffered bus). If the
buffer is to be permanently connected into the system then all the
separate pull-up resistors should be combined. But if it is to be
connected by adding it onto an existing system, then only those on
the additional I
bus if the original system is required to be able to still operate on a
stand-alone basis.
A further restriction is that the maximum pull-up current, with the bus
LOW, should not exceed the I
or 30mA on the Buffered bus. The following formula applies:
1998 Jan 09
I
2
30mA u
C bus extender
2
C bus nodes and the Buffered bus. Thus it is possible to
V
2
CC
C bus system can be combined onto the Buffered
R
* 0.4
P
2
C bus specification maximum of 3mA,
2
C bus nodes
6
Where: R
If this condition is met, the fall time specifications will also be met.
Figure 4 shows typical loading calculations for the expanded I
bus.
Sx, Sy, I
Because the two buffer circuits in the 82B715 are identical either
input pin can be used as the I
clock line.
Lx, Ly, Buffered Bus, LDA or LCL
On the buffered low impedance line side, the corresponding output
becomes LDA and LCL.
V
In normal use the power supply voltages at each end of the low
impedance line should be comparable. If these differ by a significant
amount, noise margin is sacrificed.
CC
, GND — Positive and Negative Supply Pins
P
2
= scaled parallel combination of all pull-up resistors.
C Bus, SDA or SCL
2
C Bus SDA data line, or the SCL
Preliminary specification
82B715
2
C