FAQ: Logic and Voltage Translation > IxC >> I2C IO Expander Schematic Checklist
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IO Expander Checklist |
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Status (good, bad, okay, ?) |
Comment |
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Local Decoupling Capacitors |
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Generally, a 0.1-uF capacitor is placed on VCC, as close to the device as possible |
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Verify the schematic pinout matches the data sheet pinout |
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Check that the pullup resistors are present on the SDA and SCL net within the schematic. |
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Unused GPIO pins are biased to either VCC or GND via resistor |
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Most of TI's IO expander portfolio do not include internal pull-up resistors on the p-port pins; the exceptions are PCF8575, PCF8574, PCF8574A, TCA9555|PCA9555, PCA9554|TCA9554, and TCA9554A|PCA9554A and therefore can be left floating. An alternative approach is after powering up the device, any unused p-port pins can be set as an output (does not matter if set high or low). |
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Device address is unique on the bus unless using an I2C switch or I2C MUX to resolve conflicts |
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If the device has a /RESET pin, bias the pin high (preferably with a pull-up resistor) after powering up. |
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If the device has a /INT pin and the /INT pin is used, tie this pin to a pull-up resistor. |
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