topic Re: Problems with NVT2010 in Other NXP Products

Problems with NVT2010

alvarohernando — Thu, 06 Oct 2016 17:05:15 GMT

Hello, I am testing the bidirectional voltage-level translator NVT2010 but I am not able to make it work as expected.

I have one MK22FN256VLL12 at 3.3 V and I need to convert the signals to 1.8 V. I am using the same circuit proposed in the datasheet, with VREFB = 3.3 V and VREFA = 1.8 V.

With the MK22FN256VLL12 GPIOs configured as outputs with output logic 1 in the initialization, if I connect only the 3.3 V side, don't connect 1,8 V and left A ports floating, the VREFA value is 2.8 V. I don't know it this is normal or not.

When I connect the 1.8 V to VREFA and A ports to GPIOs configured as inputs with no pull, VREFA value is 2.1 V and the conversion is done for 3.3 V to 2.1 V instead of 1.8 V.

I have tried also with inputs with pull-up and happened the same. In tek00015.bmp it could be seen VREFA in yellow (2.1 V), A1 in blue (2.1 V when high), VREFB (2.6 V) in pink and B1 in green (3.3 V when high).

With the MK22FN256VLL12 GPIOs configured as inputs with pull-up and on the other side GPIOs configured as outputs with no pull, VREF value is still 2.1 V and the conversion is done from 1.8 V to 1.8 V instead of 3.3 V. With 1.8 V, the MK22FN256 should not read a high level (VIH = 2.31 V), but it did.

In tek00008.bmp it could be seen VREFA in yellow (2.1 V), A1 in blue (1.8 V when high), VREFB (2.6 V) in pink and B1 in green (1.8 V when high).

I don't know what I am doing wrong so any help would be appreciated.

Many thanks.

Regards,

Álvaro

Re: Problems with NVT2010

xiangjun_rong — Mon, 10 Oct 2016 03:42:46 GMT

Hi, Alvaro

Can you attach your schematics here so that we can have a review?

I suppose that you want to convert the 3.3V logoc from K22 to 1.8V logic, in the case, because the VrefB should be greater than VrefA, so you should connect 1.8V regulator to VtrefA, connect the EN and VREFB pins to 3.3V via 200Kohm pull-up resistors. Pls refer to Fig 8. Typical application circuit (switch enable control) in NVT2008_NVT2010.pdf.

The K20 output/input should be connected to B side.

Hope it can help you

XiangJun Rong

Re: Problems with NVT2010

alvarohernando — Mon, 10 Oct 2016 08:14:26 GMT

Hello Rong,

Here is the schematic. I have connected VREFB to 3.3 V and the B ports to the µc MK22FN256. I have the footprint to place 10k pull-up resistors but they are not being populated on the PCB because I am using the internall pull-ups of the µc.

The VREFA is connected to 1.8 V.

Regards,

Álvaro

Re: Problems with NVT2010

xiangjun_rong — Tue, 11 Oct 2016 06:36:16 GMT

Hi,

How about connecting the VREFB pin to 3.3V via a pull-up resistor as Fig 7. Typical application circuit (switch always enabled) rather than connecting 3.3V to VrefB directly?

Xiangjun Rong

Re: Problems with NVT2010

alvarohernando — Tue, 11 Oct 2016 08:05:16 GMT

Hello Rong,

It may be confusing because in the first image the VREFB is on the right side and in the second image is on the left side, but I have connected VREFB and EN via a 200k pull-up resistor.

Regards,

Álvaro