LDC1614 Multichannel 28 bit ENOB conversion

Tim Gerbert

Other Parts Discussed in Thread: LDC1614, LDC1612

Hello,

I got a question about conversion time with LDC1614 in multichannel mode. The register "CHx_RCOUNT" determines ENOB of bits and resolution. In datasheet the LDC1614 should be able to sample with 28 bit resolution. So if I want to have this ENOB of bits, I want to write 2^28 = 268435456 =0xFFFFFFF into register "CHx_RCOUNT".

But this register is only a 16 bit register. Is it right that then I can only get ENOB of 16?

Best Regards

Tim Gerbert

over 9 years ago

0 Chris Oberhauser66 over 9 years ago

TI__Genius 14270 points

Hello Tim,

The LDC1612 internally multiplies the programmed 16bit-wide RCOUNT by 32 for its ENOB. The additional bits of resolution are needed for reporting out the various unique codes.

Regards,

ChrisO

0 Tim Gerbert over 9 years ago in reply to Chris Oberhauser66

Intellectual 330 points

Hello ChrisO,

so it is possible to obtain real resolution of 28 bit? With maximum on reference count I could get only 22 bits (see attached figure).

Best Regards

Tim

0 Chris Oberhauser66 over 9 years ago in reply to Tim Gerbert

TI__Genius 14270 points

Hi Tim,

28bits is not realizable. but note that LDC ENOB is heavily influenced by the sensor inductance shift; if the inductance change is increased, then the ENOB can be improved. The calculation tool makes a rough estimate and does not break out the inductance shift separately. We will have an application note published soon which provide more information on LDC resolution.

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LDC1614 Multichannel 28 bit ENOB conversion