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DRV8813: Slow decay mode and MOSFET conduction on DRV8813

Fabio Bianchini
Prodigy 50 points
Part Number: DRV8813
Other Parts Discussed in Thread: DRV8814, DRV8841, DRV8842, DRV8843,

Hi,

I am using the DRB8813 in a non usual way, that is' I want to use the brake function of motor with four lower MOSFETs in ON state and upper MOSFETs in OFF state.

To achieve that, I've hard connect the AI0, AI1, BI0 and BI1 pins to 0 [Vdc] (selecting slow decay mode) and I switch the APHASE and BPHASE pins to rotate the motor: when I want brake rotation riducing power, I connect two pins AVREF and BVREF to 0 [Vdc], but the ouputs (AOUT1, AOUT2, BOUT1 and BOUT2) don't commutate to low voltage, because AOUT1 and AOUT2 continue to oscillate to 50 [KHz].

In all cases,if I drive APHASE = BPHASE = L.L.1 or APHASE = BPHASE = L.L.0, a single half of H bridge goes to low voltage and the other half oscillate to 50 [KHz].

How do I get the upper MOSFETs completely OFF and lower MOSFETs completely ON, without 50 [KHz] oscillation?

Thank you

Fabio

  • 0
    TI__Guru** 114905 points
    Hi Fabio,

    The DRV8813 was not intended to operate in this manner.

    The DRV8814 is the preferred device. When the DECAY pin is set to 0, the logic table allows LL.

    The DRV8841 and DRV8842 are also better choices for this type of operation. The DRV8841 and DRV8843 are pin to pin compatible with the DRV8813, but the interface is different.
  • 0 in reply to Rick Duncan
    Prodigy 50 points

    Hi Ricky,

    thanks for your help!

    I've another question for you anout DRV88XX series of controllers: in datasheet, Texas recommends the use of low ESR capacitors, both in the electrolytic and ceramic version. I found the electrolytic capacitors, but I don't found the ceramic capacitors defined "low ESR" connected to CP1, CP2, VCP, VMA and VMB. Can You suggest me some series of low ESR capacitors? Are the consumer capacitors (10nF, 100 nF defined "commodity") adequate to this circuit?

    Thank you in advance for help.

    Fabio

  • 0 in reply to Fabio Bianchini
    TI__Guru** 114905 points

    Hi Fabio,

    Ceramic capacitors are typically low ESR  when compared to electrolytic.

    We typically recommend X7R ceramic capacitors (-55C to 125C, +/-15%)

    A good starting point for the ceramic capacitors you seek is the Bill of Materials for the DRV8813EVM. The EVM hardware files can be found here: