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I am using PCA9685 in a project. 3 are on the same i2c bus and thus I need to change the address of individual ICs. It has 5 selectable address bits as shown in the figure below:

PCA

The address will change depending on whether A0...A5 are tied to GND or VCC.

Datasheet says that:

To conserve power, no internal pull-up resistors are incorporated on the hardware selectable address pins and they must be pulled HIGH or LOW.

Does it mean I need to use external resistors for pull up or pull down or am I allowed to directly connect the address pins to GND or VCC as per my requirement?

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You can do both. What they mean is that, if you connect the pin to either GND or VCC, there will be no current wasted due to some internal pull-up/pull-down.

But whether you connect it directly or through a resistor does not really matter. I suggest you connect them directly for simplicity.

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  • \$\begingroup\$ Thanks dim. To save component cost and PCB space, I am going to tie the pins directly to VCC and GND. \$\endgroup\$ – Whiskeyjack Oct 18 '16 at 13:18
  • \$\begingroup\$ That is what I'd do as well. I edited my post accordingly, by the way. \$\endgroup\$ – dim Oct 18 '16 at 13:19
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    \$\begingroup\$ In a production design, your test engineer might prefer you connect through a resistor so the tester can override the pull-up/down and test the chips connectivity completely. In a hobby project, you don't need to worry about this. \$\endgroup\$ – The Photon Oct 18 '16 at 15:37

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