PCA9539: Pca9539 equivalent with OE or enable pin

As far as I know, such an expander does not exist.

You can disable a specific output by configuring the pin as an input.

Thanks for your suggestion. 

Here are the details of requirement in our automation product.

We program all the GPIOs of expander with logic 1 or logic 0 via i2c based on our input data, 

Once the programming is done, we turn on the outputs for specific time frame eg: 200ms and then turn off for 100ms and then turn on for 200ms again.

To achieve this, an OE or EN pin would be very helpful in my view, but if we can achieve the same operation with control registers programming, we would be happy to chose above suggested part.

Please let us know if its possible 

Thanks

Thanks for your suggestion Mastermind.

Our application is a bit real time and we use 30 16 bit expanders to control 480 pins as logic 1 or logic 0.

As to disable/enable the outputs by writing config registers, we would have overhead of i2c addressing and communication handshakes for 30 parts almost in a single stretch.

If we can have OE pin or EN pin, I can short all OE/EN pins of 30 parts and use it to turn ON or OFF for specific time periods without having the communication overheads for almost real time data.

Any suggestions are greatly appreciated 

Currently I am using PCA9698 which has OE pin, but it's lead times and cost are not friendly for our startup. 

Hi Gopi,

We do not currently offer any /OE pin on our I2C IO expanders. The next best thing would be to conduct the 30 I2C writes to each of the IO expanders. Are you using FM+ ? 

Any interest in SPI IO expansion for faster data rates? 

Regards,

Tyler

Thanks for the suggestion. 

SN74HCS595/SN74AHC595/SN74LV595A looks like 8 bit expanders, any possibility of 16 bit expanders, please let us know.

And we also need the output pins as logic 0 by default for our application.

Explored TLC5928, it fits well but all outputs are high by default.

Hi Tyler,

Thanks for help. We are not using FM+ and we might be interested in SPI too if required.

Coming to 30 I2C writes with addressing, we will do it as a final option.

We are great full for all your support to get us a feasible solution for our application 

The only 16-bit shift register is the SN54LS673, for legacy military applications. Cascaded '595 devices behave like a large shift register.

You can initialize the shift registers before pulling /OE low.

Thanks clemens.

Is R/W the OE pin in this chip or something else, please suggest 

Thanks 

As far as I know, pulling /CS high disables all I/Os. But I am not recommending the SN54LS673.

Hi Tyler,

• I am not sure we can incorporate SN54LS673, as pulling /CS would reset the serial data too along with disabling IOs.
• We are working on TLC5928 currently, but looks like the default IO state is logic 1 or high in the part.

Thanks

There is no integrated device that does what you want.

I am not aware of any similar device that has default-low outputs. It would be possible to implement a shift register with flip-flops with clear inputs that can be set by a reset signal, but that would require many chips. Do you really require default-low in hardware? Can't you initialize the shift register during power up (when /OE is high)?

In practice, an application like this would be implemented with cascaded '595 shift registers.

Thanks Tyler,

Reprogramming will not be the best option for our application currently. Appreciate the help received. 

Thanks

Hi Gopi,

If no further questions, I will close the thread. 

Thanks,

Regards,

Tyler