LMP92066: How to fill LUTs?

Arijeet Saha

Part Number: LMP92066

Hi Team,
We are using LMP92066_DAC, in these, we are able to get internal temperature sensor output (12 bit). but from the software side how to fill LUT 0 and LUT 1 (lookup tables) using temp output? what is the calculation for these?

over 3 years ago

0 Paul_Frost over 3 years ago

TI__Guru 53573 points

Hi Arijeet,

Section 8.3.2.1 and Section 9.2.1.2 of the LMP92066 datasheet cover this is pretty deep detail, so I recommend that you start there. Note that this DAC is designed to vary the DAC voltage based on the temperature sensor input. That means that you must know what you want the dac output transfer function should look like against temperature. You might be able to find this in your power amplifier's datasheet or you will need to characterize the PA's drain current across temperature to determine your desired curve.

Thanks,

Paul

0 Arijeet Saha over 3 years ago in reply to Paul_Frost

Prodigy 160 points

Can you please give an example of filling the DEL register? (with taking any temperature value ) . ?

0 Arijeet Saha over 3 years ago in reply to Arijeet Saha

Prodigy 160 points

Hi,

1) we are filling LUT registers (DEL0 to DEL38) with values 0x11, 0x22 ....., 0xEE (as per datasheet). We kept base voltage 2.25 (24`c). so our output voltage is varying from 2.25 volt to 2.5-volt w.r.t input temperature varying (-28 to 127-degree Celcius ).

why output voltage is not going up to 5 volts and why output voltage not decreasing below 2.25 volts?

2) How to calculate LUT values for the second channel? because we want to fill different values in LUT0 and LUT1. (for DAC0 and DAC1 ) .

3) How to change baseline value (voltage) at 24 degrees Celcius ? for eg. if want to give baseline voltage = 3 volt.

4) According to the baseline value how LUTs registers ( DEL0 to DEL38 ) value will change? Can you please give us an example for these?

+1 Paul_Frost over 3 years ago in reply to Arijeet Saha

TI__Guru 53573 points

Please look at my most recent post on this thread:https://e2e.ti.com/support/data-converters/f/data-converters-forum/981497/lmp92066-calculate-luts-for-lmp92066-dac

0 Arijeet Saha over 3 years ago in reply to Paul_Frost

Prodigy 160 points

Hi Paul,
Thanks for your reply, I will refer to this post.

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LMP92066: How to fill LUTs?