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DRV8305: DRV8305 and TPS54040

Manu Abraham
Genius 3510 points
Part Number: DRV8305
Other Parts Discussed in Thread: TPS54040

Hi,

Can someone please throw in some light on the 2 questions that I am having ?

#1. There are 3 DRV8305 variants. (no LDO, 3.3V LDO and 5V LDO variant)

Does the PGOOD signal behave the same for the "no LDO" variant as with the 3V/5V LDO variant ?

(I was unable to find a satisfactory answer from the datasheet)

#2.

Both the TPS54040 and the DRV8305 both generate PGOOD signals.

Ref designs show the MCU is RESET using the PGOOD signal from the DRV8305.

Should the MCU be RESET from the PGOOD from the DRV8305, or from the TPS54040 ?

Thanks,

Manu

  • 0
    TI__Guru 61330 points

    Manu,

    Thanks for posting on the MD forum!

    #1: Please check the following section for the PWRGD options for all three variants: 7.3.9.4 VREG Undervoltage (VREG_UV)

    #2: This is up to you, it depends on your design.

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Genius 3510 points

    HI Adam,

    Thanks for the reply. Let me ask my question again in another way:

    Actually, Section 7.3.9.4 causes a bit of confusion at my end:

    "The VREG output set point is configured for two different levels, 3.3 V or 5 V,
    depending on the DRV8305 device options (DRV83053Q and DRV83055Q)."

    and

    "The PWRGD is taken low until the undervoltage condition is removed and for at least a minimum of 56 μs."

    Reading both of them in context, does that mean:

    PWRGD signal is valid only on the 3.3V and 5V variants only and not applicable for the "no regulator: (VREF) device option (DRV8305NQ
    and DRV8305NE). ?

    Because of this confusion, Question #2 came up in my thought process. ie, can I switch between the LDO variant and the no LDO variant, while I do use the PWRGD signal from the DRV8305NE/NE variants. Does that work ?

    Thanks,

    Manu

  • 0 in reply to Manu Abraham
    TI__Guru 61330 points

    Manu,

    The last sentence of that paragraph explains: "Note that the VREG undervoltage monitor is disabled on the no regulator (VREF) device option (DRV8305NQ and DRV8305NE)."

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Genius 3510 points

    Adam,

    Yes, thanks for the clarification.

    Best Regards,

    Manu