If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Part Number: TL431-Q1

Hi team,

My customer is evaluating our TL431Q1 product, they would like to know is that a must requirement for the following resistors R1, R2 accuracy be 0.1%, could it also be OK with accuracy 1% R1 and R2? Thank you!

• Hi Zirui

It depends on the error budget you are looking for. Let's say  you are using 0.1% resistor and gain of 2 , in that case max mismatch will be 100.1k and 99.9K in R1 and R2. Hence max error in gain will be 0.1%. This error will increase to 1% in case you are using 1% resistance tolerance.  Error due to resistance mismatch will increase with gain.

Hence maximum possible error % in VKA due resistor will increase 10 times when tolerance is changing from 0.1% to 1%. This error will get added in initial accuracy which is close to 2% [min - 2.440 , typ - 2.495 , max - 2.550V].

Regards

Trailokya

• Hi Rai,

Thanks for your reply. Now we would like to have an example calculation for our better understanding, please kindly help to check whether it is correct:

If both R1 and R2 customer use 0.1%, 10k resistors, please kindly confirm that whether they could obtain VO according to the following formula and table:

Note: Vref is 2.495 (typical), 2.470 (min), 2.520 (max) :

 Typical % MIN MAX R1 10.000k 0.10% 9.990k 10.010k R2 10.000k 0.10% 9.990k 10.010k Vref 2.495v 2.470v 2.520v Vo 4.99 0.10% 4.985 4.995

In addition, there is another question, please help to confirm: Does the different value of Vsup input voltage also affect the result of VO output?

If I design directly according to Figure20, the Vka output is 2.47V~2.52V? Is that correct?

• Hi Rai,

Any feedback from your side? Customer is evaluating our device, thank you!

• Hi Zirui

This gain error is calculated based on typical Vref for figure 27. VREF max to min will add extra error.

Figure 20 will not have much impact from R1 accuracy.

Regards

Trailokya

• Hi Trailokya,

Thanks and customer is still wondering about the Fig 20 whether their understanding is correct: They would like to know the Vka value calculation based on Fig 20

"If I design directly according to Figure20, the Vka output is 2.47V~2.52V?"

• Zirui

R2 in infinite in case for fig 20 so Vka = (1 + R1/(Infinite))*VREF so VKA will be equal to vref in that case irrespective of resistor tolerance value.

Regards

Trailokya