Is it safe to connect PCA9671 outputs to ground?

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Is it safe to connect PCA9671 outputs to ground?

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pete_scott
Contributor II

The PCA9671 features a quasi-bidirectional output, where a 100 uAmp pullup current is applied to the IO when configured high.  The datasheets lists a high livel output current of maximum 300 uAmps and a typical transient boosted pullup of 1 mA under the conditions VOH=VSS.  Does this imply that it is safe to connect the IO pins directly to ground?

Many thanks.

4 Replies

154 Views
lisettelozano
NXP Employee
NXP Employee

 Hello Pete.

No, it should not cause damage. And we do not see any issue to connect the I/O pins to ground. The I/O pins are by default High. In this situation, they are internally pulled high by a weak pull-up current and they can be pulled LOW by an external signal when they are being used as an input. As a remark, if a HIGH is applied to an I/O which has been written earlier to LOW, a large current (IOL) will flow to VSS.

Have a great day,

Paulina

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pete_scott
Contributor II

Thanks Paulina.  Presumably, this high current when a low IO is written high is the 1 mA typical transient current listed in the datasheet.

Cheers,

Pete.

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pete_scott
Contributor II

Hi Paulina,

Many thanks for replying to my question.  The information that you provided doesn't state whether it is safe to connect these IOs to ground.  When setting the output high, will the current through the transient pullup transistor to ground cause damage?  Can the 100 uA constant current source be connected directly to ground through the high side FET?

Cheers!

Pete.

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lisettelozano
NXP Employee
NXP Employee

Hello Peter,

The I/Os are set to HIGH for default after power-on. As you can see in Fig 2 on the datasheet, there is a transistor connected between the I/Os and VSS. When a ‘0’ is written, the transistor is on and forces the I/O to go to LOW.

I hope this information can be helpful.


Have a great day,

Paulina

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