TPD3E001: question about VCC connection

TS Yang

Part Number: TPD3E001

Dear TI,

Below is the whole schematic applying TPD3E001DRL related to this matter.

Here, when the RA7 is applied, the status of the USB OTG ID signal is as shown below,
This shows that VBUS is flowing backward or leaking into the ID signal inside the TPD3E001DRL.

I tried to attach 0.1UF attach close to Vcc,
and increase Ra7 resistor value up to 10K, but the same.

Do you know these cases and how to improve them? or is it OK to open VCC (RA7)?

ps.> Rather, when OTG external devices are connected, the fixed voltage is maintained.

Symptoms occur when USG OTG con. is left open without connecting anything.

thanks,

over 6 years ago

0 Alec Forbes over 6 years ago

TI__Expert 3500 points

TS-

Can you clarify what you mean by "Vbus is flowing backwards"? It looks to me like the oscilloscope image shows a clean waveform.

If you do not apply the Vbus bias pin to Vcc, it will mean that the Vbus line will not have ESD protection and that there will be higher capacitance on the data lines, however that might be acceptable.

Thanks,

Alec

0 TS Yang over 6 years ago in reply to Alec Forbes

Genius 4800 points

Alec,

The waveform is shown when open with nothing in the USB OTG Con.
USB VBUS is output by OTG_EN of U16, and OTG_EN is connected with OTG_ID.
Waveform appears only when OTG_ID is connected to VCC of TPD3E001DRL
When VCC is disconnected, no waveform appears.
Is it normal to have that waveform on OTG_ID?

TS

0 Cameron Phillips over 6 years ago in reply to TS Yang

TI__Genius 12410 points

Hello,

How is OTG_ID connected to OTG_EN? It is not shown on the schematic.
Also where is that waveform coming from? Is that the Vbus pin? or the enable pin?

Regards,
Cameron

0 Cameron Phillips over 6 years ago in reply to Cameron Phillips

TI__Genius 12410 points

Also I believe that waveform is the result of the 3V3 pullup on the ID line that you have where any time the Vbus isn't present the 3V3 will drive through the forward diode of the TPD3E001. Is this the problem that you are seeing?

Regards,
Cameron

0 TS Yang over 6 years ago in reply to Cameron Phillips

Genius 4800 points

Hi Cameron,

The driver is set to OTG_ID = OTG_EN.
The waveform captured above is the waveform of OTG_ID.
Vbus outputs according to OTG_ID = OTG_EN
OTG_ID is always high when there is no USB OTG connector due to 3.3V pullup.
Eventually, Vbus will output
It is a problem that OTG_ID (RA7) oscillates like the waveform according to the Vbus connection.

thanks,

0 Cameron Phillips over 6 years ago in reply to TS Yang

TI__Genius 12410 points

My recommendation would be not connect VCC pin or use a different part that doesn't have a VCC pin.
We have an app note explaining why VCC is not needed in our newer parts
www.ti.com/.../slyt561.pdf

Regards,
Cameron

Interface

Interface forum

TPD3E001: question about VCC connection