NVT2006 level converter - SPI fail

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NVT2006 level converter - SPI fail

4,399 Views
rifattursen
Contributor I

Hello,

We are using NVT2006 level converter IC for SPI signals but level conversion doesn't work.

MCU side is at 3.3V
ADC side is at 5V

We use NVT2006 in between but ADC side signals are at 2V
We bypassed NVT2006 and verified that ADC and MCU are working as expected.
NVT2006 fails to level translate. Can you please guide us regarding this problem?

Attached you can find the schematic and a list of things we tried to solve the problem

* VrefA side goes to STM32 and since 5V - 3.3V > 1V, no pullups were placed there
* Soldered an external 10K resistor pulling up pin 13 (B2) to 5V
* removed R103 and connected EN pin to VrefB pin
* Populated C119 to see if it helps

None of the above solved the problem, SDO signal from U46 is still at 2V logic level, this should have been 5V's

Can you please comment regarding this issue?
Best Regards

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16 Replies

4,289 Views
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Contributor I

Nope, it doesn't work.

A side is directly connected MCU

We have 4 pullups connected VrefB,

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4,368 Views
guoweisun
NXP TechSupport
NXP TechSupport

Hi

For your schematic:

1:A side need pull up to VCCA without resistor,B side need pull up to VCCB with 1.74k resistors.

2:EN directly connect with VREFB and pull up to VCCB with a 200K resistor.

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4,361 Views
rifattursen
Contributor I

Hi,

Thank you for your answer.

So you mean

1- A side doesn't need pull-ups. All four signals at B-side requires 1.74K even if they are SPI(push-pull) which is our case.

2- Short out EN and VREFB, desolder R103.

 

Am I correct? Thanks for your support.

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4,357 Views
guoweisun
NXP TechSupport
NXP TechSupport

HI

You are correct!

 

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4,346 Views
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Contributor I

Hello,

B side signals seems to be okey now but A side signal below (taken below from stm32 Miso input) doesn't reach GND

You can see the oscilloscope output. nvt2006_2nd_Trial.jpeg

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4,312 Views
guoweisun
NXP TechSupport
NXP TechSupport

For the A side ,you can disconnect with the MCU side directly test the NVT2006 Aside signal.

 

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4,303 Views
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Contributor I

and how do you expect me feed the SPI signal if I disconnect the MCU?

 

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4,298 Views
guoweisun
NXP TechSupport
NXP TechSupport

Could you please share the update schematic to check again?

 

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4,341 Views
guoweisun
NXP TechSupport
NXP TechSupport

A side also try to pull up without resistor to VCCA.

 

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4,334 Views
rifattursen
Contributor I

Hello,

How can I pull up A side SPI signals without using resistors to 3.3V?

 

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4,328 Views
guoweisun
NXP TechSupport
NXP TechSupport

 

 

 

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4,323 Views
rifattursen
Contributor I

I am sorry but I can't do that

Stm32 will surely not be able to drive SPI signals once it's connected directly to 3.3V supply.

Are you sure you are not meaning something else?

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4,314 Views
guoweisun
NXP TechSupport
NXP TechSupport
  • In case you miss something please share with your update schematic now!

 

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4,358 Views
guoweisun
NXP TechSupport
NXP TechSupport

 

 

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4,393 Views
guoweisun
NXP TechSupport
NXP TechSupport

Could you please share with the schematic?

 

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4,390 Views
rifattursen
Contributor I

Hello,

I thought that I attached it in the first post but the resolution looks really bad. Below I post the schematic

nvt2006.png

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