DRV8842: Datasheet parameters

Kamran1

Part Number: DRV8842

Hello,

I am using the DRV8842 to control a brushed12 V DC motor. The MCU I am using that will contorl the DRV8842 is supplied with 5VDC. I am intending to direclty connect the MCU pins (V_Hi = 5V) to the DRV8842 digital pins.

If I understood correctly from the datasheet, only the Vref pin of the DRV8842 is a 3.3 V input, the rest of inputs can be driven with 5V level, is that correct?

Page of the datasheet states that V_iH is 2.2V min and 5.25V max (in the absolute max rating, the max voltage is 7V). What does 5.25V value indicates?

Thank you!

over 6 years ago

0 Pablo Armet over 6 years ago

TI__Mastermind 37683 points

Hi Mohamad,

Q: "If I understood correctly from the datasheet, only the Vref pin of the DRV8842 is a 3.3 V input, the rest of inputs can be driven with 5V level, is that correct?"

[Answer]: Yes, the Vref pin can be driven with a max of 3.5 V and the rest of the logic inputs have a high input voltage of 5.25V.

Q: "Page of the datasheet states that V_iH is 2.2V min and 5.25V max (in the absolute max rating, the max voltage is 7V). What does 5.25V value indicates?"

[Answer]: 5.25V is the maximum input voltage for high logic in the digital pins. If a voltage higher than 5.25V is connected to the pins, it could potentially damage the device.

0 Kamran1 over 6 years ago in reply to Pablo Armet

Prodigy 50 points

Hi Pablo,

Thank you for you response. But if 5.25V damages the chip, so why the absolute max rating is 7V?

Are not these info contradicts?

Thank you

0 Pablo Armet over 6 years ago in reply to Kamran1

TI__Mastermind 37683 points

Hi,

I am sorry. I meant to say that the device might not function properly if the voltage is above 5.25V.

0 Kamran1 over 6 years ago in reply to Pablo Armet

Prodigy 50 points

Hi Pablo,

Thank you for your reply. Another question relaed to the same driver. Looking at the reference design (CPG004) I see 330 ohm resistors between the MCU and the driver digital interface (The MCU and the motor driver are supplied with 3.3V). Could you please explain the utility of these resistors?

Thank you!

0 Pablo Armet over 6 years ago in reply to Kamran1

TI__Mastermind 37683 points

Hi Mohamad,

Could you send me a link to the reference design? I was not able to find it on ti.com

0 Kamran1 over 6 years ago in reply to Pablo Armet

Prodigy 50 points

Hi Pablo,

Here it is: http://www.ti.com/tool/DRV8842EVM

check Design Files.

Thank you!

0 Pablo Armet over 6 years ago in reply to Kamran1

TI__Mastermind 37683 points

Hi Mohamad,

Thank you for the link. Just so we are on the same page, are you talking about the resistors shown below?

0 Kamran1 over 6 years ago in reply to Pablo Armet

Prodigy 50 points

Hi Pablo,

Yes exactly. What is the reason to have them?

Thank you!

0 Pablo Armet over 6 years ago in reply to Kamran1

TI__Mastermind 37683 points

Hi Mohamad,

Those resistor are there to allow the customer to remove the MSP430 MCU in the EVM and connect another MCU. The resistor can be removed to disconnect the digital interface from the MSP430 and allow another MCU to be connected in its place.

0 Kamran over 6 years ago in reply to Pablo Armet

Intellectual 270 points

Hi Pablo,

Thank you for your response. So there were no issue with the motor driver/MCU that prompted the addition of those resistors.

A note on the schematic could have helped.

Thanks!

0 Pablo Armet over 6 years ago in reply to Kamran

TI__Mastermind 37683 points

Hi,

You are correct. Like I said, the resistors are only there to break the digital interface with the MSP430 MCU if needed.

0 Kamran over 6 years ago in reply to Kamran

Intellectual 270 points

Hi Pablo,

But still, we usually use 0 Ohm resistor for such purpose. But here 220 Ohm were used!

Could you please double check?

Thanks!

0 Pablo Armet over 6 years ago in reply to Kamran

TI__Mastermind 37683 points

Hi Kamran,

The decision to use 220 ohm was made by the designer of this EVM. The 220 ohm resistor should not affect the performance of the EVM in any way.

0 Kamran over 6 years ago in reply to Pablo Armet

Intellectual 270 points

Hi Pablo,

Thank you for your support on this issue!

Regards!

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DRV8842: Datasheet parameters