Questions to RP-Range. Internal behavior of the LDC.

Daniel Schmidt

Hello TI Community,

is there any additional information what RP_min and RP_max do change inside of the LDC1000.

N1: I noticed that drift seems to by high if a small Rp_min is selected.

N2: Some RP_min and RP_max combinations seem to suffer from higher noise than others.

N3: The results of RP do often strongly depend on the selected Rp-Range. How can i get trustworthy results of Rp-range to use for calibration.

In addition:

N4: If my smallest rp-range settings are(for example) 16k and 21k. If i lower RP_min step by step it clips of at 4k even if the range got larger and my RP measurement should be in range. What is happening there internally?

over 10 years ago

0 Natallia Holubeva1 over 10 years ago

TI__Expert 6550 points

Hello David,

Rp values set current limits that LDC1000 drives into the LC tank aka sensor. Rp max sets the low limit of the current, where Rp min sets the high limit. Please, see the picture below.

Best Regards,

Natallia Holubeva

0 Daniel Schmidt over 10 years ago in reply to Natallia Holubeva1

Prodigy 70 points

Thanks Natallia,

you helped me a lot to understand the LDCs operation a bit more.

But: What tells the LDC to cut of maximum current and get to the minimum current supply? Is it based on the amplitude or maximum power supplied?

Thank you,

Daniel

0 Natallia Holubeva1 over 10 years ago in reply to Daniel Schmidt

TI__Expert 6550 points

Hello Daniel,

The Rp and Vpp (amplitude) do. If you are using the GUI, you set the amplitude to a certain Vpp. You also set Rp values. Then, using V=IR, the current is set. Please note that the actual current in the LC tank is Q(quality factor)* Current you set.

Best Regards,

Natallia Holubeva

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Questions to RP-Range. Internal behavior of the LDC.