TPS25846-Q1: Handshaking is not working properly.

Nagaravi Yarlagadda

Part Number: TPS25846-Q1

Tool/software:

Hi Team,

Does this IC automatically manage the handshaking with DP_IN & DM_IN pins or i need to use any other controller along with this? I didn't connect any resistors on these lines and DP_OUT & DM_OUT are left open. and CTRL1 & CTRL2 are pulled high to select CDP mode.

I don't need any communication on data lines.

Only some mobiles are charging and some mobiles and tabs are not charging. By shorting D+ & D- on USB port, all mobiles and tabs are charging.

What is the fix to make it as universal charger with current limit up to 2A apart from shorting D+ & D-. I set overload trip threshold at 2.5A and it's working good.

5 months ago

0 Chuck Branch 5 months ago

TI__Mastermind 32691 points

Nagaravi,

The TPS25846-Q1 supports BC1.2 CDP and SDP negotiation only. You are describing DCP negotiation and that standard is not supported by the TPS25846=Q1.

Regards,

Chuck

0 Nagaravi Yarlagadda 5 months ago in reply to Chuck Branch

Prodigy 10 points

Hi Chuck,

I was expecting CDP from the device. I didn't added any resistance on D+ and D- in the original design. After i found some mobiles and tabs are not working, i made it into DCP by shorting D+ and D-.

My question is if i configure in CDP mode, do i need to add any extra resistors on D+ and D- lines or IC internal function can take care of handshaking?

0 Chuck Branch 5 months ago in reply to Nagaravi Yarlagadda

TI__Mastermind 32691 points

Do you have a HUB that will respond to the enumeration on the USB bus to complete the BC1.2 negoation?

CDP mode requires that an enumeration be started on the bus

Regards,

Chuck

0 Nagaravi Yarlagadda 5 months ago in reply to Chuck Branch

Prodigy 10 points

I am testing with mobiles. Samsung A51 and iPad pro are working and iPhone 14pro max, Samsung S24, iPhone mini are not working.

Regards,

Naga Ravi

0 Chuck Branch 5 months ago in reply to Nagaravi Yarlagadda

TI__Mastermind 32691 points

Naga,

Can you send me a screen capture of the schematic that shows how the TPS25846-Q1 is connected?

Regards,

Chuck

0 Nagaravi Yarlagadda 5 months ago in reply to Chuck Branch

Prodigy 10 points

Hi Chuck,

Do not confuse with GND symbol near USB connector. it was passing through another connector. It was connected to power ground only.

Regards,

Naga Ravi

0 Chuck Branch 5 months ago in reply to Nagaravi Yarlagadda

TI__Mastermind 32691 points

Naga,

This schematic will not support CDP or SDP because there is no connection to any HUB or source to execute the enumeration that is required and the TPS25846-Q1 does not support DCP, so BC1.2 charging will not work in this schematic as drawn.

Regards,

Chuck

0 Nagaravi Yarlagadda 5 months ago in reply to Chuck Branch

Prodigy 10 points

Hi Chuck,

Then please suggest the needed modifications to make this support BC1.2. I assumed the converter will take care as there is a BC1.2 block inside the block diagram and control pins are given to select the mode.

Regards,

Chuck

+1 Chuck Branch 5 months ago in reply to Nagaravi Yarlagadda

TI__Mastermind 32691 points

Nagaravi,

The only suggestion I can offer is to put a 200 ohm resistor across DP_OUT and DM_OUT to advertise that mode of BC1.2. This is a valid connection, but this use is outside of the TPS25846-Q1 design. The TPS25846-Q1 is always intended to be connected to a USB host port and this system is actually attempting to be a DCP.

Regards,

Chuck

0 Nagaravi Yarlagadda 5 months ago in reply to Chuck Branch

Prodigy 10 points

Hi Chuck,

Thanks for the suggestion.

Regards,

Naga Ravi

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TPS25846-Q1: Handshaking is not working properly.