DRV2625: about auto-calibration

ACGUY

Other Parts Discussed in Thread: DRV2625, DRV2604L, DRV2605L

Hello E2E,

Our customer is considering adoption the DRV2625 for next resonant device module.
Few days ago, they obtained the DRV2625-EVM, and connected with their resonant device.
The resonant device resonant frequency is 100Hz, resonant impedance is about 15-ohm.
Initially, auto-calibration process is not Done, and GUI status collar is Red. Resonant frequency was been set to maximum.
I suggested register address 0x2A value to modify from default to 0x02. PROCESS_DONE flag is "1".
However, the resonance frequency was set to the maximum without changing.
With other resonant device connected, DRV2625-EVM is indicates a normal value.

Q
:Does TI grasp similar case?
:Does the DRV2625 have restrictions on the impedance of resonant devices?
:If TI has idea for resolv, please let us know it.

Regards,
ACGUY

over 5 years ago

0 Luis Fernando Rodriguez S. over 5 years ago

TI__Guru* 84915 points

Hello,

The DRV2625 has some restrictions that could avoid a proper operation of the resonance tracking algorithm.

We recommend to ensure that the recommended operating conditions of datasheet (www.ti.com/.../drv2625.pdf are respected. Could you verify if the Load capacitance is below 100pF? Do you have a datasheet of the resonant device that is causing this status?

Thank you.

Best regards,
Luis Fernando Rodríguez S.

0 Luis Fernando Rodriguez S. over 5 years ago in reply to Luis Fernando Rodriguez S.

TI__Guru* 84915 points

Hello,

Excuse me, do you have any update regarding this issue? Could you find out the root cause?

Please let us know if you have any observation.

Best regards,
Luis Fernando Rodríguez S.

0 ACGUY over 5 years ago in reply to Luis Fernando Rodriguez S.

Guru 11170 points

Hello,

Thank you for reply.
I am asking various characteristics of resonant devices to customers.
I will report it in a fewdays.

Regards,
ACGUY

0 Luis Fernando Rodriguez S. over 5 years ago in reply to ACGUY

TI__Guru* 84915 points

Hello,

Thank you for your feedback.

We will be waiting for customers response.

Best regards,
Luis Fernando Rodríguez S.

0 ACGUY over 5 years ago in reply to Luis Fernando Rodriguez S.

Guru 11170 points

Hello Luis,

I confirmed parasitic capacitance of customer's LRA.
f0=around 80-Hz, L0=0.07H at resonant, Z=15-ohm without resonant.
=> C0=around 56uF!! Too large!!!

Does TI have an appropriate haptic driver for this resonant device?
or
Does TI think that DRV2604L can operate this resonant device?

Regards,
ACGUY

0 Luis Fernando Rodriguez S. over 5 years ago in reply to ACGUY

TI__Guru* 84915 points

Hello, ACGUY,

Since the capacitance is too high, could you try increasing the Drive, Current-Dissipation & Blanking Times?

www.ti.com/.../drv2625.pdf

This may help to get a correct auto-calibration.

Please let me know if you have different results.

Best regards,
Luis Fernando Rodríguez S.

0 Luis Fernando Rodriguez S. over 5 years ago in reply to Luis Fernando Rodriguez S.

TI__Guru* 84915 points

Hello, ACGUY,

Excuse me, did you have the chance to take a look at my questions above? Is there any update about this?

Thank you.

Best regards,
Luis Fernando Rodríguez S.

0 ACGUY over 5 years ago in reply to Luis Fernando Rodriguez S.

Guru 11170 points

Hello Luis,

Sorry. I sent your advice to our customer, however i don't obtain reply not yet from them.
I confirm about it to them soon.

Regards,
ACGUY

0 Luis Fernando Rodriguez S. over 5 years ago in reply to ACGUY

TI__Guru* 84915 points

Hello, ACGUY,

Thank you for your feedback. We will be waiting for your response.

Please let us know if you need anything from our side.

Best regards,
Luis Fernando Rodríguez S.

0 ACGUY over 5 years ago in reply to Luis Fernando Rodriguez S.

Guru 11170 points

LRA_Z and_C.pdfHello Luis,

Customer measred the AC charactics for 2-types LRA. Please see the attached file.
Type LVC : Parasitic capacitance = 56uF
Type USZ : Parasitic capacitance = 1.2uF
Device spec : max 100pF

I was sent your advice to customer.
"Address 0x27 : Default value 0x10h -> 0x9Fh"
"Address 0x28 : Default value 0x11h -> 0xFFh"
The GUI succeeded in automatic calibration of LRA(LVC type), but the resonance frequency slightly swings every try.

Customers also tried different LRA (USZ type).
Resonant frequency = 228 Hz
C = 1.2 uF
The parasitic capacitance of the USZ type is smaller than the LVC type, but it is larger than the specification (max 100 pF) of the data sheet.
However, automatic calibration succeeded normally for USZ type and it works normally.

Why does auto calibration succeed in USZ type LRA?
Please let me know your opinion.

Regards,
ACGUY

0 Luis Fernando Rodriguez S. over 5 years ago in reply to ACGUY

TI__Guru* 84915 points

Hi, ACGUY,

Having a large capacitance will slow down the settling time of the BEMF voltage measurements and it may affect the algorithm. Even if it is partially working, it is not suggested to have capacitance as high as 56uF.

1.2uF may work since it is much smaller, but if possible, please reduce the value to the suggested capacitance in datasheet. It will ensure that the algorithm will work 100% of times.

Best regards,
Luis Fernando Rodríguez S.

0 ACGUY over 5 years ago in reply to Luis Fernando Rodriguez S.

Guru 11170 points

Hello Luis,

Thank you for answer. I do like to question again.
DRV2605L has not limit for load capacitance. Do you think that does DRV2605L can drive the 56uF capacitance LRA?
or
Are there concerns when using a resonant device with a load capacitance of 56 uF to the DRV2625 at a fixed frequency?

Regards,
ACGUY

0 Luis Fernando Rodriguez S. over 5 years ago in reply to ACGUY

TI__Guru* 84915 points

Hello, ACGUY,

There will be always a concern with the load capacitance if you are looking to use the auto-calibration feature. It directly affects to the algorithm when a high value is used.

Best regards,
Luis Fernando Rodríguez S.

0 ACGUY over 5 years ago in reply to Luis Fernando Rodriguez S.

Guru 11170 points

Hello Luis,

In other words, if not use the auto-calibration, has not affects to the algorithm?

Best regards,

ACGUY

0 Luis Fernando Rodriguez S. over 5 years ago in reply to ACGUY

TI__Guru* 84915 points

Hello, ACGUY,

You are right. The high capacitance values are not recommended since it may affect the auto-calibration algorithm behavior. If this feature is not used, you may configure the parameters manually. It may help to drive the resonant devices with high capacitance value.

Best regards,
Luis Fernando Rodríguez S.

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DRV2625: about auto-calibration