TCA9517-Q1: EN Pin configuration and question on Topography

Veerasamy Vasudevan

Intellectual 390 points

Part Number: TCA9517-Q1

Tool/software:

Hi,

I have couple of basic questions.

1. Can I leave the EN pin floating? Will the device be fully functional if this pin is floating

2. The datasheet mentions about problems in connecting the B-Side to another B-side device. I did not fully understand the problem - I believe the issue is that the VOL of B side output is 0.5V and since the VIL of B side needs to be 0.43V or less, we cannot connect B side to B side. Am I correct in my understanding? In my application, we dont have multiple I2C buffers. In that case, can I connect B side to any target device as long as the Vol of that target device is less than 0.43V? I am planning to connect the B-Side to the Power supervisor IC "UCD9090ARGZR". Will it work?

Regards,

Veerasamy

10 months ago

0 Jack Guan 10 months ago

TI__Mastermind 41256 points

Hi Veerasamy,

1.) No, the EN pin is a CMOS logic input and should not be left floating as the pin will be in an unknown state. If unused, a weak pulldown can be used to hold device in low state and EN up via external GPIO pin.

2.) Yes, this is right. TCA9517-Q1 has a static voltage offset on B-side for the output low voltage that is also referred to as the "buffered low". It allows the device to recognize which side of the device is driving low to prevent an internal lockup state. The B-B side connection won't work as the VOL of the 2nd buffer will not be recognized by the first device as a valid low and can cause contention issues. In your case, It is advised for device on B-side to be able to achieve a lower VOL than the VILC requirement in the datasheet.

Regards,

Jack

0 Veerasamy Vasudevan 10 months ago in reply to Jack Guan

Intellectual 390 points

Hi Jack,

Thanks for the reply. In the datasheet, page 10 under Block diagram, there is a pull up resistor connected internally to the EN pin. So can I let this pin floating, if I want the device to be always enabled?

Regards,

Veerasamy

+1 Jack Guan 10 months ago in reply to Veerasamy Vasudevan

TI__Mastermind 41256 points

Hi Veerasamy,

I see- in your case that the device is always enabled, EN can be left floating. It is in the event of the disabled state that requires additional design considerations, see similar E2E thread: https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1284705/tca9517-q1-output-behavior-when-en-l/4871696?tisearch=e2e-sitesearch&keymatch=tca9517%252525252525252520float#4871696

Regards,

Jack

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TCA9517-Q1: EN Pin configuration and question on Topography