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DRV612 GAIN setting Mechanism

KANJI SHIBATANI
Mastermind 6205 points
Other Parts Discussed in Thread: DRV612

Hello

I had checked DRV612 EVM to compare the ' Fail ' sample ' (Gain= 16dB from customer's board )

and 'Good 'one  (Gain=3.5dB)  when Rgain=51Kohm.

Attached is the 'Good' sapmle (EVM) wave form.

We see some glitch ( internal circuit start up and seems proper operation for internal charge pump something )

 when Vdd is over 2.8V at  ''Good' sample.

Also, when Vdd is over the 1.9V , GAIN voltage goes up.

Here is the question.

Q1  Is these waveform  proper operation? ( Would you please check in  TI USA?)

      Customer had  found there are no glitch on GAIN terminal on ' Fail' sample on customer's board, but

     found glitch on 'Good' sample.

Q2  Would you please describe how DRV612 internal circuit works at the Power up for Gain-setting?

      I need more detail internal block diagram for DRV612 also.

 

 

Customer is using DRV612 for their STB from  a few years ago, but  they found  3pcs/1500pcs were illegal gain (16dB, all of 3pcs) 

even Rgain=51Kohm.

I have doubt for customer's board( noise of Vdd line)

Best Regards

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  • 0
    TI__Intellectual 2285 points

    Hello Kanji, 

    Q2: The programmable Gain setting follows a state machine which after condition, connect a specific value of Rin to a specific value of Rf, to set the Gain since internally an ADC read the value of the external resistor and active the switches in order to get the right Gain.

    Q1: This means a lot of Logic and switching when the part is active (Active mode at 2.8V when the chargepump switch to full strength mode) so this creates some noise.. This is why you can see some glitch in the beginning of the new gain setting on the "good" part.

    We will have a deeper look on one of our EVM.

    Regards,
    Mohamed Hellal

  • 0 in reply to Mohamed Hellal
    Mastermind 6205 points

    Dear Mr Hellal,

    Thank you for your quick reply.

    I appreciate your support!

    Best Regards

  • 0 in reply to KANJI SHIBATANI
    TI__Intellectual 2285 points

    Dear Mr. Shibatani,

    I checked the mechanism gain waveform of one DRV612 EVM and the glitch confirm the internal circuit start up as said above.

    Regards, 

    Mohamed Hellal