PIC16C77X_13 Datasheet, PDF (95/202 Pages) Microchip Technology – 28/40-Pin, 8-Bit CMOS Microcontrollers w/ 12-Bit A/D

PIC16C77X
8.3 Connection Considerations for I²C
Bus
For standard-mode I²C bus devices, the values of
resistors R_p R_s in Figure 8-42 depends on the following
parameters
• Supply voltage
• Bus capacitance
• Number of connected devices
(input current + leakage current).
The supply voltage limits the minimum value of resistor
R_p due to the specified minimum sink current of 3 mA
at VOL max = 0.4V for the specified output stages. For
example, with a supply voltage of VDD = 5V+10% and
VOL max = 0.4V at 3 mA, R_{p min} = (5.5-0.4)/0.003 =
1.7 k VDD as a function of R_p is shown in Figure 8-42.
The desired noise margin of 0.1VDD for the low level
limits the maximum value of R_s. Series resistors are
optional and used to improve ESD susceptibility.
The bus capacitance is the total capacitance of wire,
connections, and pins. This capacitance limits the max-
imum value of R_p due to the specified rise time
(Figure 8-42).
The SMP bit is the slew rate control enabled bit. This bit
is in the SSPSTAT register, and controls the slew rate
of the I/O pins when in I²C mode (master or slave).
FIGURE 8-42: SAMPLE DEVICE CONFIGURATION FOR I²C BUS
VDD + 10%
R_p
R_p
DEVICE
R_s R_s
SDA
SCL
NOTE: I2C devices with input levels related to VDD must have one common supply
line to which the pull up resistor is also connected.
C_b=10 - 400 pF
 1999-2013 Microchip Technology Inc.
Advance Information
DS30275B-page 95