Compiler/OPT3101: The phase_out on reg8 is inverted with the distance

HAUT Alain

Part Number: OPT3101

Tool/software: TI C/C++ Compiler

Hello,

We would like use the OPT3101 for a new product for our company but I have several difficulties to use it. We have choiced a laser diode ADL-65103TL (our future customer has need to see the beam) with the photodiode SFH213. We have realized a board with the recommendations of your notice SBAU350B and the optical head with this same notice. We have used the notice SBAU310 for the calibration. We have a good beam with the good current but when I read the phase_out in the register 8 we have the value which decrease with the distance and increase when the target is near of the emitter. I don’t know why? Can you help me?

Thank you by advance.

Best Regards.

Alain

over 4 years ago

0 Alex Bhandari-Young over 4 years ago

TI__Mastermind 25895 points

Hi Alain,

Has calibration been performed on the board? Without calibration the OPT3101 data is not usable. Also could you explain what you mean by optical head?

Best,

Alex

0 HAUT Alain over 4 years ago in reply to Alex Bhandari-Young

Prodigy 100 points

Hi Alex,

The calibrations (indicate in SBAU310) frequency calibration, illumination crosstalk, phase offset calibration and phase correction with ambient have been made.

I got the following results:

Designation	Register	Value in hex
ILLUM_XTAL_REG_SCALE	2E[19-17]	7
IPHASE_XTALK_REG_HDR0_TX0	2F [15-0]	5C18
QPHASE_XTALK_REG_HDR0_TX0	30 [15-0]	C998
IPHASE_XTALK_REG_HDR1_TX0	31 [15-0]	8D2C
QPHASE_XTALK_REG_HDR1_TX0	32 [15-0]	26EA
TMAIN_CALIB_HDR0_TX0	47 [11-0]	908
TMAIN_CALIB_HDR1_TX0	48 [11-0]	910
PHASE_OFFSET_HDR0_TX0	42 [15-0]	B238
PHASE_OFFSET_HDR0_TX1	51 [15-0]	FFFF
AMB_PHASE_CORR_PWL_X0	B8 [9-0]	4
AMB_PHASE_CORR_PWL_X1	B8 [19-10]	A
AMB_PHASE_CORR_PWL_X2	B9 [9-0]	28
AMB_PHASE_CORR_PWL_COEFF0	0C[23-16]	64
AMB_PHASE_CORR_PWL_COEFF1	B4 [7-0]	55
AMB_PHASE_CORR_PWL_COEFF2	B4 [15-8]	B0
AMB_PHASE_CORR_PWL_COEFF3	B4[23-16]	3
SCALE_AMB_PHASE_CORR_COEFF	B5 [2-0]	2
AMB_CALIB	0B [23-14]	2F

We have an optical head which contains the lens for laser diode to focus the beam and we have two independents filters to suppress the ambient light to protect the photodiode.

Thank you for your help.

Best Regards

Alain

0 HAUT Alain over 4 years ago in reply to HAUT Alain

Prodigy 100 points

Hi Alex,

I’m sorry but I have always the problem of inverted phase. I have replayed the different calibration and I have these results:

Designation	Register	Value in hex
ILLUM_XTAL_REG_SCALE	2E[19-17]	7	Illumination crosstalk
IPHASE_XTALK_REG_HDR0_TX0	2F [15-0]	103E
QPHASE_XTALK_REG_HDR0_TX0	30 [15-0]	1546
IPHASE_XTALK_REG_HDR1_TX0	31 [15-0]	8648
QPHASE_XTALK_REG_HDR1_TX0	32 [15-0]	0F6C
TMAIN_CALIB_HDR0_TX0	47 [11-0]	920	Phase offset calibration
TMAIN_CALIB_HDR1_TX0	48 [11-0]	920
PHASE_OFFSET_HDR0_TX0	42 [15-0]	08C7
PHASE_OFFSET_HDR0_TX1	51 [15-0]	952
AMB_CALIB	0B [23-14]	2F
AMB_PHASE_CORR_PWL_X0	B8 [9-0]	4	Phase correction with ambient
AMB_PHASE_CORR_PWL_X1	B8 [19-10]	A
AMB_PHASE_CORR_PWL_X2	B9 [9-0]	28
AMB_PHASE_CORR_PWL_COEFF0	0C[23-16]	64
AMB_PHASE_CORR_PWL_COEFF1	B4 [7-0]	55
AMB_PHASE_CORR_PWL_COEFF2	B4 [15-8]	B0
AMB_PHASE_CORR_PWL_COEFF3	B4[23-16]	3
SCALE_AMB_PHASE_CORR_COEFF	B5 [2-0]	2
INT_XTAL_REG_SCALE	2E[16-14]	7	Internal crosstalk
IPHASE_XTALK_INT_REG	3D[15-0]	29B6
QPHASE_XTALK_INT_REG	3E [15-0]	5800

If I mask the photodiode, I have an amplitude of 1023 (during internal crosstalk and illum crosstalk). But in standard detection if I mask the photodiode i have an amplitude of 6300 in this condition, the FORCE_SCALE_VAL is 3, are you agreed?

If I don't mask the photodiode and without target the amplitude decrease to 2500, it's normal?

For the Phase Offset Calibration, AMP_OUT is 6500 at maximum, I cannot have more. I don’t know why with a laser diode of 10mW with a current of 31mA. The beam is very good. It’s a problem with the FORCE_SCALE_VAL?

Thank you in advance for your answer. I'm loose.

Best Regards

Alain

0 Alex Bhandari-Young over 4 years ago in reply to HAUT Alain

TI__Mastermind 25895 points

Hi Alain,

This crosstalk is very high. The crosstalk amplitude with masking the photodiode after running calibration should be < 50 codes to do any usable testing and < 20 codes for real use. Before calibration crosstalk of 1000 may be correctable but depends. For reference out EVM has crosstalk before calibration of 100-200 and after calibration of <10. Have you followed the PCB design guidelines in the system design doc? If you would like to post design files and info I can take another look.

Best,

Alex

0 HAUT Alain over 4 years ago in reply to Alex Bhandari-Young

Prodigy 100 points

Hi Alex,

Yes, we have followed the PCB design guidelines in your doc SBAU305B and we have edited your files gerber of the EVM to design our PCB. I add the pictures of our design and thank you in advance if you can indicate me the different problems that you'll see.

I don’t understand why your register FORCE_SCALE_VAL can have a value between 0 to 7 if it’s impossible to suppress an amplitude upper 1000 when I mask the photodiode? It's not indicated in your docs.

Thank you for your times and your quickly answers.

Best Regards

Alain

PCB design.docx

0 Alex Bhandari-Young over 4 years ago in reply to HAUT Alain

TI__Mastermind 25895 points

Hi Alain,

This is documented in 2.4 Crosstalk and performance in this doc

https://www.ti.com/lit/ug/slau791/slau791.pdf?ts=1606157507589

This covers how to handle high crosstalk as well as target crosstalk levels. I would advise checking the steps to see ways to handle the crosstalk you are seeing.

Regarding the board design, if you can include labels for the components, specifically the LED then I can review further.

Best,

Alex

0 HAUT Alain over 4 years ago in reply to Alex Bhandari-Young

Prodigy 100 points

Hi Alex,
I found the problem of crosstalk, it come from of the separates grounds with a ferrite like your EVM schematic. I replaced the ferrite by a short circuit and now I have a crosstalk of 57 after internal crosstalk and illum crosstalk correction. It is ok or always too much?
Now, I would like to proceed at phase offset calibration but I have only AMP_OUT>10000 at a short distance (20cm max). In this configuration, after proceed at phase offset calibration, I have only the good phase at a short distance (<40cm) after this distance (50cm...) it’s a wrong value of phase. It is only a problem of power of emitting light?
Thank you in advance for your answers.
Best regards
Alain

0 Alex Bhandari-Young over 4 years ago in reply to HAUT Alain

TI__Mastermind 25895 points

Hi Alain,

What is the amplitude at the bad reading? Amplitude of ~200 or 300 or higher should not have much error.

Best,

Alex

0 HAUT Alain over 4 years ago in reply to Alex Bhandari-Young

Prodigy 100 points

Hi Alex,

Thank you for your answer.

I have continued the different settings and now I can measured a distance until 3m (with illum_dac_L or illum_dac_h) but no more. I don’t understand why I can not detect after 3m with illum_dac_h?

If I can detect a distance until 3m with illum_dac_l, I don’t understand why I can’t detect much more with illum_dac_h. Have you an idea to resolve my problem? At a distance of 4m, I have an amplitude of 172.

Thank you in advance.

Best Regards.

Alain

0 Alex Bhandari-Young over 4 years ago in reply to HAUT Alain

TI__Mastermind 25895 points

Hi Alain,

With crosstalk of 50 and amplitude of 172 you may be getting some error. In that case you would need to increase light received by the RX. You can estimate the error from crosstalk by plugging into the formula in this app note www.ti.com/.../sboa315.pdf

Best,

Alex

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Compiler/OPT3101: The phase_out on reg8 is inverted with the distance