ISO224EVM: Output through the TLV6001 path

michaelwu

Part Number: ISO224EVM
Other Parts Discussed in Thread: ISO224, TLV6001

Based off of the suggestion from a previous E2E post that I made, I'm implementing a differential to single-ended output conversion using TLV6001 like the one in the ISO224 EVM.

However, I'm a little bit confused. Based on my hand calcs, it seems that the output of TLV6001 is Voutp - Voutn + Vdd, so there's an entire Vdd level shift up because of the offset introduced at the non-inverting input. So, if my goal is to have simply Voutp-Voutn at the output of TLV6001 so that I can feed the output into a microcontroller, shouldn't I just divide Voutp in half at the non-inverting input? Because then this gives me

Vo = Voutp/2 - 105k*((Voutn - Voutp/2) / 105k)

This gives me Voutp - Voutn at the output, which is what I'm looking for.

Regards,

Michael

over 5 years ago

0 Alexander Smith over 5 years ago

TI__Mastermind 47595 points

Hi Michael,

This: www.ti.com/.../sbaa229.pdf
and this thread should help: e2e.ti.com/.../762040

0 michaelwu over 5 years ago in reply to Alexander Smith

Intellectual 460 points

Thanks, this is helpful. I guess I just have maybe a couple more questions...

On the app note, it seems that Voutn has a + before it in the equation, whereas intuitively (and based on the derivation shown in the post) Voutn should be subtracted, is that correct?

If that's true, then it seems pretty straightforward what I need to do, Vcm will be tied to ground, and R2/R1 = R4/R3 = 1. Let me know if this sounds right.

Regards,
Michael

0 Alexander Smith over 5 years ago in reply to michaelwu

TI__Mastermind 47595 points

Hi Michael,

You are correct, it is adding (+) a negative voltage (-) which in this case results in subtraction (-) as you pointed out. This equation is used so that it can be applied to any voltage magnitude, whether it be positive or negative. I forgot to link this cookbook circuit that should help as well: www.ti.com/.../sbaa317.pdf

Take a look at 3. of the Component Selection section. Your resistor values and Vcm level will be dependent on the input range of the MCU ADC.

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ISO224EVM: Output through the TLV6001 path