MCF8315D: how to handle the external 5V used for pull up when power off the 24Vcc..

Ernest Cho

Part Number: MCF8315D

Hi team,

My customer would use additional switch for the 24Vcc on/off. ( for turn off the MCF8315D VCC manually/externally by MCU when they are needed. do not want to use sleep mode.)
But currently their schematic for 5V is not using FB_BK 5V but using 5V for their main MCU.

At this condition, they would like to turn off their 24Vcc and question is :
- do they also have to turn off the 5V rail for MCF8315D which is mostly related to pull ups(I2C, FG, nFAULT, etc)?

If there is no issue to stay 5V for MCF8315D side then they would like to turn it on when they turn off the 24Vcc.

I guided them to use FB_BK 5V but they would like to sustain their schematic on their current project due to the schedule.

Best regards,
Ernest

2 months ago

+1 Venkatadri Shantaram84961 2 months ago

TI__Mastermind 28062 points

Hi Ernest,

We can maintain a 5V pull-up on the pin while the MCF8315D is powered off. This is a general use case and is also applicable for the Speed pin.

The absolute maximum rating is 6V.

Could you share the schematics for review?

Thanks and Best regards

Venkatadri S

0 Ernest Cho 2 months ago in reply to Venkatadri Shantaram84961

TI__Expert 3341 points

Hi Venkatadri,

Thank you for your comment.

I will send you an separate email for schematic.

Regards,
Ernest

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MCF8315D: how to handle the external 5V used for pull up when power off the 24Vcc..