ntb0104

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ntb0104

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madroche90
Contributor I

Hello,

I am wondering if the following situation will damage the NTB or NTS devices at all. 

VCCA is tied to a local 1.8V regulator that will always be on once the board is powered up. VCCB is tied to a header for external devices and may either be floating or tied to ground through 1k resistor until power is applied to the header. The OE enable pin is tied low through a pull down resistor until driven high by a GPIO from the processor or by VCCB. 

Will the device be damaged if VCCA is 1.8V, VCCB is tied low or floating (please address both situations in your response) and OE is low and tri states signals until VCCB comes up and then is driven high for signal translation. 

Please let me know! 

Thank you 

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6 Replies

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guoweisun
NXP TechSupport
NXP TechSupport

Hi,

Under your condition, NTB or NTS devices will not be damaged!

Thanks!

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madroche90
Contributor I

Okay thank you!

Can you confirm that I can tie OE to VCCB? Even though it is internally referenced to VCCA?

Does this mean that OE needs to be equal or high to VCCA in order to enable the device?

Madeleine

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guoweisun
NXP TechSupport
NXP TechSupport

Hi,

OE cannot be connected to Vccb.

OE buffer is seating on Vcca domain.

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madroche90
Contributor I

Okay thank you for the response.

I have follow-up questions now.

Our configuration is that VCCA will turn on to 1.8V as soon as power is applied to the board, but VCCB will not turn on until the user applies power to an external header at some time later. I read in the datasheet that if either VCCA or VCCB is not present that the device will be in shutdown mode. My questions are:

1. Is the device safe while VCCA and OE are high and VCCB is not?

2. If yes, should VCCB be grounded or floating while not powered?

3. Can OE be tied directly to VCCA for the above configuration? Or would you suggest driving it with a GPIO until VCCB goes high?

Please let me know asap as we have the board in layout and need to make changes asap.

4. If I wanted to share a schematic page with you for review, how would I go about that without posting it to the forum?

Thanks!

Madeleine

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guoweisun
NXP TechSupport
NXP TechSupport

Hi

Please give me your mail address about your schematic and your concern questions!

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153 Views
madroche90
Contributor I

Madeleine.roche@intel.com<mailto:Madeleine.roche@intel.com>

Please email me asap! Thanks.

Madeleine

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