TCA6408A-Q1 Datasheet, PDF (26/40 Pages) Texas Instruments – Low-Voltage 8-Bit I2C and SMBus I/O Expander With Interrupt Output

TCA6408A-Q1
SCPS234 – SEPTEMBER 2016
9.2 Typical Application
Figure 31 shows an application in which the TCA6408A-Q1 can be used.
V_CCI
(1.8 V)
V_CCP
(3.3 V)
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10 k
V_CC
(x 4)
Master _SCL
Controller
SDA
INT
GND RESET
V_CCI V_CCP
SCL
P0
SDA
INT
RESET
P1
TCA6408A-Q1
P2
P3
P4
P5
P6
ADDR P7
GND
100 k
(x 3)
Subsystem 1
(e.g., Alarm)
ALARM
(see Note D)
ENABLE
Keypad
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A. Device address configured as 0100000 for this example.
B. P0 and P2–P4 are configured as inputs.
C. P1 and P5–P7 are configured as outputs.
D. Resistors are required for inputs (on P-port) that may float. If a driver to an input will never let the input float, a resistor
is not needed. Outputs (in the P-port) do not need pull-up resistors.
Figure 31. Typical Application Schematic
9.2.1 Design Requirements
9.2.1.1 Calculating Junction Temperature and Power Dissipation
When designing with the TCA6408A-Q1, it is important that the Recommended Operating Conditions not be
violated. Many of the parameters of this device are rated based on junction temperature. So junction temperature
must be calculated in order to verify that safe operation of the device is met. The basic equation for junction
temperature is shown in Equation 1.
T_j = T_A + (q_JA ´ P_d )
(1)
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