XTR106: Vref and Vreg voltage is zero in XTR106

Amir Poursadegh

Part Number: XTR106

I have to design a 4-20 mA transmitter circuit for a load cell with 520ohm impedance.

I used XTR106 and circuit that mentioned in figure 5 of XTR106 datasheet.

but i don't have any Vref voltag for supplying my sensor means the voltage is zero so my current is zero too. (Vreg is zero too)

my circuit is:

I don't know what is the problem. maybe the the XTR106 was damaged but all 5 ICs that i bought had a same result.

I would be thankful if someone could help me...

over 6 years ago

0 kai klaas69 over 6 years ago

Guru 140200 points

Hi Amir,

why do you have a GND connection at the bridge? Take care, don't connect anything of the XTR106 circuit to GND!

Kai

0 Amir Poursadegh over 6 years ago in reply to kai klaas69

Prodigy 235 points

my sensor has a wire for shield....
what would be happened if i connect GND to my XTR106 circuit ?...I'm sure it would be ok if I connect pin7 to GND for example

0 kai klaas69 over 6 years ago in reply to Amir Poursadegh

Guru 140200 points

Hi Amir,

the whole XTR106 circuit is floating and the voltage at pin 6 is shifted by the voltage drop of output current across burden resistance (the load resistance which is connected from pin 3 to pin 2 of connector P1). So, you must not connect pin 7 or any other pin of XTR106 to GND!

And it's not wise to use GND as a shield for the bridge either. Connect the shield to pin 6 instead. But take care that pin 6 is not connected to any foreign potential!

Kai

0 Amir Poursadegh over 6 years ago in reply to kai klaas69

Prodigy 235 points

Hi Kai
thanks for your helpful answers... I will correct my circuit
but my question is why I don't have Vref voltage? is it related to Vref and Vreg voltage?

0 kai klaas69 over 6 years ago in reply to Amir Poursadegh

Guru 140200 points

Hi Amir,

I don't know. Eventually, the XTR106 was destroyed by unintentionally connecting GND to the XTR106?

I would correct the circuit and check it with a fresh XTR106.

Kai

0 Amir Poursadegh over 6 years ago in reply to kai klaas69

Prodigy 235 points

How I could be sure that XTR106 was destroyed or not? is it a check test for it?

0 kai klaas69 over 6 years ago in reply to Amir Poursadegh

Guru 140200 points

Hi Amir,

if your circuit is correct and the XTR106 is ok, then the circuit should work. If not, then there might be an error left in the circuit or the XTR106 might be damaged.

The schematic you have shown, is it complete or are there any extensions using GND? What is the purpose of the "Span" signal at pin 1 of P1?

Kai

0 Amir Poursadegh over 6 years ago in reply to kai klaas69

Prodigy 235 points

Hi Kai

It's not complete I have another part for cut the circuit and give constant current...but I test this circuit alone without another thing and results was same (i didn't use sheild pin as you mentioned)...are you sure if I connect GND to pin 7 of XTR106 (with a mosfet), the XTR106 would be damaged?

0 kai klaas69 over 6 years ago in reply to Amir Poursadegh

Guru 140200 points

Hi Amir,

can you show the schematic with the MOSFET?

Kai

0 Amir Poursadegh over 6 years ago in reply to kai klaas69

Prodigy 235 points

Hi Kai

this is the whole of my circuit

AD694 do it's duty well but XTR106 is not.

0 Amir Poursadegh over 6 years ago in reply to Amir Poursadegh

Prodigy 235 points

maybe use a Rload is necessary for get response but in this situation the voltage of Io would be constant in my case...

0 Amir Poursadegh over 6 years ago

Prodigy 235 points

for test of XTR106, i get constant 1V between Pin2 and pin5 but the current was zero...is it means the IC was damaged? (in this situation I didn't use pin6, pin14 and pin11)

0 kai klaas69 over 6 years ago in reply to Amir Poursadegh

Guru 140200 points

Hi Amir,

you have no Rload connected to the XTR106?

Kai

0 Amir Poursadegh over 6 years ago in reply to kai klaas69

Prodigy 235 points

in the past no but now I put a 100ohm resistor between pin2 and pin3 of P1 connector for Rload

0 kai klaas69 over 6 years ago in reply to Amir Poursadegh

Guru 140200 points

Hi Amir,

is it working with the Rload then?

Kai

0 Amir Poursadegh over 6 years ago in reply to kai klaas69

Prodigy 235 points

Hi Kai

unfortunately no...

0 kai klaas69 over 6 years ago in reply to Amir Poursadegh

Guru 140200 points

Hi Amir,

try with a fresh XTR106. Remove all this MOSFET stuff and remove the AD694.

Kai

0 Amir Poursadegh over 6 years ago in reply to kai klaas69

Prodigy 235 points

Hi Kai

so you think the XTR106 was damaged...

0 kai klaas69 over 6 years ago in reply to Amir Poursadegh

Guru 140200 points

Hi Amir,

yes, looks like. Just take a fresh XTR106 and try again. It's very simple to make the XTR106 run properly, usually, provided you wire the XTR106 exactly as recommended in the datasheet.

Kai

0 Amir Poursadegh over 6 years ago in reply to kai klaas69

Prodigy 235 points

Hi Kai

I test with a fresh XTR106 and now I have Vref, Vreg and 4mA output current... now I have another question about figure 5 of XTR106 datasheet and I'm going to use new thread for it

0 kai klaas69 over 6 years ago in reply to Amir Poursadegh

Guru 140200 points

Hi Amir,

nice to hear that you could solve the issue!

Kai

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XTR106: Vref and Vreg voltage is zero in XTR106