TPS65981: GPIO or I2C Control of Internal Vbus Power Switch

Daniel Neasmith

Part Number: TPS65981
Other Parts Discussed in Thread: TPS25750,

Hello,

We are looking to control the power output (VBus) to an LCD connected through USB-C. The intent is to have a mode where the screen is powered off while our system is still functional. We are trying to understand whether (and how) it may be possible to control the internal switches between VBus and PP_5V0 externally, but have not been able to find any info in the docs. A method using GPIO is preferred if possible.

Thank you very much,

Daniel

over 4 years ago

0 Hari Patel1 over 4 years ago

TI__Genius 12700 points

Hi Daniel,

For new designs, I would recommend using the TPS65987DDH or if you need just power sourcing/sinking, you could also look into the TPS25750.

As far as controlling the signals externally, you may need an EC/Host to communicate to the PD controller via I2C.

Could you elaborate any scenarios where you would use this?

Thank you,

Hari

0 Daniel Neasmith over 4 years ago in reply to Hari Patel1

Prodigy 40 points

Hi Hari,

Thank you for the recommendation on parts, I will look into them as well.

The USB-C device that we have connected to the TPS65981 will remain attached at all times. Because of this, when the system is on, the device will receive power to the voltage at the PP_5V0. However, we want to have the ability for the system to be powered and function without the device being turned on and receiving power. Basically, we are just trying to avoid having a high amperage switch, and since the PD controller has switches for its power delivery we are trying to access and control them via a GPIO.

Just to confirm, if GPIOs are not an option but I2C is, would the control be register 0x28, bits 25:24, on page 24 of the below doc?

www.ti.com/.../slvuan1a.pdf

I hope that makes more sense, let me know if I can give further clarification.

Thank you,

Dan

0 Daniel Neasmith over 4 years ago in reply to Hari Patel1

Prodigy 40 points

Hi Hari,

Additional point from the other parts you mentioned - our system needs -30 Celsius rating, so we cannot use the TPS65987DDH, and we need the alt mode DP, so we cannot use the TPS25750.

Thank you,

Dan

0 Hari Patel1 over 4 years ago in reply to Daniel Neasmith

TI__Genius 12700 points

Hi Dan,

I see yes for the temperature requirements this would be correct. I will take a look into the specific registers this would require and provide additional feedback next week.

Thank you,

Hari

0 Daniel Neasmith over 4 years ago in reply to Hari Patel1

Prodigy 40 points

Sounds great, thank you Hari.

0 Hari Patel1 over 4 years ago in reply to Daniel Neasmith

TI__Genius 12700 points

No worries, I am still looking into this.

+1 Hari Patel1 over 4 years ago in reply to Hari Patel1

TI__Genius 12700 points

Hi Daniel,

I have found that for this type of operation, you will need to use the 4CC SRDY/SRYR I2C commands and unfortunately will not be able to use GPIO. Therefore, the registers you will need to configure are I2C master configuration and global system configuration which can select the Master port.

Thank you,

Hari

0 Daniel Neasmith over 4 years ago in reply to Hari Patel1

Prodigy 40 points

Hi Hari,

Thank you for the reply. Do you know if the I2C_IRQZ is required for this type of operation, or is it made more for 'alarm' situations? My base instinct is that the answer is 'no', as it is an output and we are just intending to control the VBUS power output, but I want to verify.

Thank you,

Dan

+1 Hari Patel1 over 4 years ago in reply to Daniel Neasmith

TI__Genius 12700 points

Hi Daniel,

Are you referring to just the I2C_IRQ pin? Where do you see the IRQZ? The I2C_IRQ will just be an interrupt sent to the master (EC) to alert when something has changed/triggered. The interrupt triggers can be set in the Interrupt Mask registers. However, no this is not necessary.

Thank you,

Hari

0 Daniel Neasmith over 4 years ago in reply to Hari Patel1

Prodigy 40 points

Hi Hari,

The pin is labelled as I2C_IRQZ in the TPS65981 datasheet. Either way thank you, that's what I figured, just wanted to verify. I should be good now!

Thank you for your time,

Dan

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TPS65981: GPIO or I2C Control of Internal Vbus Power Switch