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DRV421: Optional Schottky Diodes

Yutong Ren
Prodigy 40 points
Part Number: DRV421
Other Parts Discussed in Thread: DRV411

Tool/software:

Hi everyone,

does anybody know in which case the optional schottky diodes are needed? And what is the purpose of this? If I use an external amplifier (supplied by +/-15V), then in this part of circuit, the diodes are also needed to be connected between +/-15V I guess? 

Thanks in advance!

  • 0
    TI__Mastermind 32140 points

    Hello Yutong,

    This is described in the datasheet in section 8.1.2.  Basically if high current pulses are expected on the primary you need to add protection for the current spikes expected on the compensation coil due to the transformer effect.  Basically you are causing a large current spike and the diodes are there to protect the inputs of the AINP and AINN pins.  Also the ICOMP1 and ICOMP2 pins but the other pins are more sensitive.

    Regards,

    Javier

  • +1 in reply to Javier Contreras4
    Prodigy 40 points

    Hello Javier,

    understand, thank you very much. In data sheet it says max. 6V beyond the supply rails, so if I use this external amplifier like in this grafic, the diodes schould be clamped between +/-15V or in this case 6V plus supply voltage (5V) only 11V?

  • 0 in reply to Yutong Ren
    TI__Mastermind 32140 points

    Hello Yutong,

    If you are using an driver then you would need to protect the driver as that is what will be driving the inductance.  Unless there is a path to the ICOMP pins it should not be an issue.  If you are using this type of circuit make sure the GND pin and low side of LDO are connected together and LDO can support the 30 V.  Here is an example full design: https://www.ti.com/lit/ug/tidu820/tidu820.pdf  The example uses a DRV411 but the DRV421 uses a flux-gate and is more accurate.  The output drive of the coil is the same principal.

    Regards,

    Javier