# Regarding Logic Level Sifter Using Voltage Compactor (HIGH 3V and LOW 2V)

1. ## Regarding Logic Level Sifter Using Voltage Compactor (HIGH 3V and LOW 2V)

Hi All.

I need to connect my MCU with an external SPI device which have Logic levels of HIGH 3V and LOW 2V. From the Device to MCU Logic shift I can convert the Voltage 3V/2V to 5V/0V respectively using LM339. But I am facing problem in the other direction conversion of 5V/0V to 3V/2V. I looked for LM311 but As my needed output of LOW Logic is not GND or -Ve hence I can not use it.

Can anyone advice any comparative Circuit or IC which I can use to make the LOW Output a Positive Voltage (i.e. 2V)? It will be great if there any Quad Differential Comparator available.

Thank you in advance.

Regards.

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2. ## Re: Regarding Logic Level Sifter Using Voltage Compactor (HIGH 3V and LOW 2V)

Hi,

I don't know any srandard logic device that needs 2V as Low level.
I assume you misunderstood the circuit or the datasheet.

Please show us your circuit (hand drawn is OK) with exact part names. Maybe post the datasheets...or a link.

Klaus

3. ## Re: Regarding Logic Level Sifter Using Voltage Compactor (HIGH 3V and LOW 2V)

Hi, Thanks.

So far I did this to convert the 2V LOW and 3V HIGH Pulse to a 0V Low and 5V High Pulse. And its working OK using LM339.

But I need to do the reverse direction as well ... i.e. convert 0V LOW and 5V HIGH Pulse to a 2V LOW and 3V HIGH Pulse. Can you advice how to do?

Regards.

4. ## Re: Regarding Logic Level Sifter Using Voltage Compactor (HIGH 3V and LOW 2V)

Hi

What is your "external SPI device" that needs a 2V LOW level?
Exact part name, datasheet.

Klaus

5. ## Re: Regarding Logic Level Sifter Using Voltage Compactor (HIGH 3V and LOW 2V)

Assuming the 2..3V is true (don't actually believe), a simple voltage divider would do the trick.

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6. ## Re: Regarding Logic Level Sifter Using Voltage Compactor (HIGH 3V and LOW 2V)

Hello.

Actually there is no Datasheet. The device is a Camera Flash Light where I like to control it by MCU though Flash Light's Hot-Shoe Interface.

I measured the signals of Camera and Flash Hot-Shoe Interface which is LOW 2V and HIGH 3V. Where my MCU Logic Level 0V LOW and 5V HIGH.

As I mentioned before ... I make the one direction conversion of 2V LOW and 3V HIGH Pulse to a 0V Low and 5V High Pulse using LM339. But can anyone suggest how to do the opposite direction i.e. convert 0V LOW and 5V HIGH Pulse to a 2V LOW and 3V HIGH Pulse?

Thanks.

7. ## Re: Regarding Logic Level Sifter Using Voltage Compactor (HIGH 3V and LOW 2V)

Hi,

I really doubt this. No one would reinvent new logic levels...

Anyway: use three resistors as voltage divider:
5V -> 2kOhm -> (3V) -> 1kOhm -> (2V) -> 2kOhm -> GND.
This generates 2V and 3V.
Connect to each of the nodes a 100uF capacitor to GND to stabilize the voltage (you could try with lower values like 10uF).
Then use a CMOS SPDT switch like 74HC4053 or 74HCT4053.
Connect the "S" to your microcontroller logic out.
Connect the "Y0" to the 2V node of the voltage divider
Connect the "Y1" to the 3V node of the voltage divider
Then "Z" is the 2V/3V level output.

Klaus

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8. ## Re: Regarding Logic Level Sifter Using Voltage Compactor (HIGH 3V and LOW 2V)

Hi KlausST. Thanks a lot. The solution looks great.

But unfortunately, I think here at my location this 74HC4053 or 74HCT4053 not available. However, I'll order it from China but will take some time to get it.

Just asking ... is it possible to get this output by using BJT's (NPN/PNP)?

Regards.

9. ## Re: Regarding Logic Level Sifter Using Voltage Compactor (HIGH 3V and LOW 2V)

Hi,

You don't show where you live...

4053' parts are relatively common ... and as written, it's just a SPDT analog switch device, I assume there are thousands different types around, from many manufacturers all over the world. Many of them will work for you.

Buy a couple of old PCB's and there is a good chance to find some SPDT analog switches.

***
If one knews about load and currents... one could surely build a circuit with BJTs.
More useful are FETs. Even a 4053 is built with FETs.

Klaus

10. ## Re: Regarding Logic Level Sifter Using Voltage Compactor (HIGH 3V and LOW 2V)

Thanks again for reply KlausST.

I found this CD4053 available here. I can use it as well ... right?

http://www.sycelectronica.com.ar/sem...4051-52-53.pdf

A --- MCU IO
ax --- 2V
ay --- 3V
OUT/IN ax or ay --- Will be the desired 2V LOW 3V HIGH output

Would you mind to advice if the connection above is Ok?

Regards.

11. ## Re: Regarding Logic Level Sifter Using Voltage Compactor (HIGH 3V and LOW 2V)

Hi,

I found this CD4053 available here. I can use it as well ... right?
As already said: we don't know all your requirements, thus it's impossible to validate.

Reading the datasheets is essential. Every professional needs to do this, too .... no one does like it.

Your pin usage seems to be OK.

Klaus

12. ## Re: Regarding Logic Level Sifter Using Voltage Compactor (HIGH 3V and LOW 2V)

Hello.

I made my circuit using CD4053 and now I cam generate the pulse of 3V HIGH and 2V LOW.

But one issue I am facing ... when I am connecting this line (SPI CLK SIgnal) to my Flash Light Device then the pulse voltage gets dropped to 2V HIGH and 1V LOW. Any comments why? Do I need any Pull-Up in 4053 Output?

Sorry that the Flash is a 3rd party device and no Datasheet available.

Regards.

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13. ## Re: Regarding Logic Level Sifter Using Voltage Compactor (HIGH 3V and LOW 2V)

Hi,

Obviously the flash draws some current at the communication signals.

Sorry that the Flash is a 3rd party device and no Datasheet available.
And there is no brand, no label, no type, no description, no photo... how can you use it?

Klaus

14. ## Re: Regarding Logic Level Sifter Using Voltage Compactor (HIGH 3V and LOW 2V)

Hi KlausST. The Flash Mode I am using is Canon 430EX ii. Hot-Shoe pins are standard for all Canon models.

Thanks.

15. ## Re: Regarding Logic Level Sifter Using Voltage Compactor (HIGH 3V and LOW 2V)

Originally Posted by KlausST
Hi,

I really doubt this. No one would reinvent new logic levels...

Anyway: use three resistors as voltage divider:
5V -> 2kOhm -> (3V) -> 1kOhm -> (2V) -> 2kOhm -> GND.
This generates 2V and 3V.
Connect to each of the nodes a 100uF capacitor to GND to stabilize the voltage (you could try with lower values like 10uF).
Then use a CMOS SPDT switch like 74HC4053 or 74HCT4053.
Connect the "S" to your microcontroller logic out.
Connect the "Y0" to the 2V node of the voltage divider
Connect the "Y1" to the 3V node of the voltage divider
Then "Z" is the 2V/3V level output.

Klaus
If you worked with any SLR cameras there is a lot of compatibility issues with the hot-shoe connector as the voltages can be different between brands, since most of them use proprietary levels for their accessories (to lock people into their ecosystem). So yeah 2V and 3V makes sense.

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