TCA6408A: TCA6408A

Hi Ian,

Ian Wang said:

Part Number: TCA6408A

Hi Sir,

Would you pls help below questions for schematic design? thanks.  

1. P0 and P2–P4 are configured as inputs.

--> These 4pins only can be input? [Bobby] All GPIOs can be configured to be either INPUTs or OUTPUTS independent of the other GPIOs

2. P1 and P5–P7 are configured as outputs.

-->These 4pins only can be output? [Bobby] All GPIOs can be configured to be either INPUTs or OUTPUTS independent of the other GPIOs

3. 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.

--> will it keep High or Low after power on? If input need to have pull-up resistors? [Bobby] At power up it is a HI-Z INPUT. All INPUTs require pull up/pull down resistors.

 4. If INT/RST need to add pull-up resistors?

[Bobby] RESET needs a pull up resistor, INT is an open drain output. If you need to use the INT pin then you need a pull up resistor otherwise it can float.

And pls kindly help review below schematic, thanks.

Thanks, Ian.

[Bobby]

• Unused pins should be either set as OUTPUTs or be referenced to GND/VCC with a resistor.
• I don't see a decoupling cap on the power rail
  
• SDA/SCL should have pull up resistors, I don't see them present
  
• RESET needs a pull up unless you plan to use a GPO to toggle high and low