NVT2006 level converter - SPI fail

[rifattursen]

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

[rifattursen]

Nope, it doesn't work.

A side is directly connected MCU

We have 4 pullups connected VrefB,

[guoweisun]

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.

[rifattursen]

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.

[guoweisun]

HI

You are correct!

[rifattursen]

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.

[guoweisun]

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

[rifattursen]

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

[guoweisun]

Could you please share the update schematic to check again?

[guoweisun]

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

[rifattursen]

Hello,

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

[rifattursen]

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?

[guoweisun]

• In case you miss something please share with your update schematic now!

[guoweisun]

Could you please share with the schematic?

[rifattursen]

Hello,

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