TPS25730: About power detection

Ryu Yamashita

Part Number: TPS25730

Hi team,

Set ADCIN1~4=(0,1,1,5).
The SINK side requires at least 7.5W (5V/1.5A), but the built-in PPHV SW turns ON even if the source side can supply only 2.5W (5V/0.5A).
The CAP_MIS signal toggles H/L to indicate a mismatch, but PPHV always outputs 5V.
Is this a TPS25730 specification?
Also, is it possible to know what power supply is connected?

Sincerely,
Ryu.

over 1 year ago

+1 Raymond Lin over 1 year ago

TI__Mastermind 34126 points

Hi Ryu-san,

The CAP_MIS is only used to indicate if a capability mismatch event has occurred, TPS25730 does not automatically disable the power path if CAP_MIS is H.

Thanks and Regards,

Raymond Lin

0 Ryu Yamashita over 1 year ago in reply to Raymond Lin

Genius 3600 points

Hi Raymond,

Thanks for the reply.
So you are saying that PPHV cannot be turned off automatically.
Also, does it mean that there is no way to detect power just by detecting mismatches?

Sincerely,
Ryu.

+1 Raymond Lin over 1 year ago in reply to Ryu Yamashita

TI__Mastermind 34126 points

Hi Ryu-san,

Ryu Yamashita said:
So you are saying that PPHV cannot be turned off automatically.
Also, does it mean that there is no way to detect power just by detecting mismatches?

Unfortunately TPS25730 does not support auto disable power path from capability mismatch detection.

Thanks and Regards,
Raymond Lin

0 Ryu Yamashita over 1 year ago in reply to Raymond Lin

Genius 3600 points

Hi Raymond,

Thanks for the reply.
I have an additional question.
The setup is the same as above, but when I used the USB A-C Cable, the mismatch signal did not go High. (A on the source side, C on the TPS25730 side)
Is this a specification?
How can I detect the available power supply of the SOURCE?

Sincerely,
Ryu.

0 Raymond Lin over 1 year ago in reply to Ryu Yamashita

TI__Mastermind 34126 points

Hi Ryu-san,

Do you know what the current capability (Rp) is the USB A-C cable capable of? If it can supply more than 1.5A (i.e. 1.5A, 2.4A or 3.0A) then the CAP_MIS will not toggle.

Thanks and Regards,

Raymond Lin

0 Ryu Yamashita over 1 year ago in reply to Raymond Lin

Genius 3600 points

Hi Raymond,

Thanks for the reply.
So if the power being supplied is out of range, but the cable itself has the ability to supply it, the mismatch will not be toggled?

Sincerely,
Ryu.

0 Christopher Lim1 over 1 year ago in reply to Ryu Yamashita

TI__Mastermind 37855 points

Hi Ryu,

Apologies for any delays, Raymond is away from the office today and will be returning Monday.

Thanks and Regards,

Chris

0 Raymond Lin over 1 year ago in reply to Ryu Yamashita

TI__Mastermind 34126 points

Hi Ryu-san,

Let me check on this and get back to you by tomorrow.

Thanks and Regards
Raymond Lin

+1 Raymond Lin over 1 year ago in reply to Ryu Yamashita

TI__Mastermind 34126 points

Hi Ryu-san,

Apologies for the delayed response. If TPS25730 does not detect PD, it will only sink up to USB default current as specified by the USB Type-C Specification:

This prevents browning out the source power since the cable is limited to only USB default power (500mA for USB2 and 900mA for USB3).

Thanks and Regards,

Raymond Lin

0 Ryu Yamashita over 1 year ago in reply to Raymond Lin

Genius 3600 points

Hi Raymond,

Thanks for the reply.
My question is whether CAP_MIS toggles in the following situation.
Set ADCIN1~4=(0,1,1,5).
Sink side requirement is 7.5W (5V/1.5A).
The USB cable can supply more than 7.5W.
The source side is limited to 2.5W, which is less than the cable's supply capacity.

Sincerely,
Ryu

+1 Raymond Lin over 1 year ago in reply to Ryu Yamashita

TI__Mastermind 34126 points

Hi Ryu-san,

TPS25730 detects current/power capability is determined by the cable's CC pull-up to Rp. Since it's not a PD to PD connection, the CC pullup is used to advertise the power the source/USB-A side can provide.

In this scenario, CAP_MIS will not toggle because the advertised power is greater than or equal to 7.5W.

Thanks and Regards,

Raymond Lin

0 Ryu Yamashita over 1 year ago in reply to Raymond Lin

Genius 3600 points

Hi Raymond,

Thanks for the reply.
I understand now.
I have one question, if the A-C cable is not PD, the advertised power is USB default power (500mA for USB2 and 900mA for USB3), but if this is the case, it will be less than 7.5W, so I think CAP_MIS will be toggled.

Sincerely,
Ryu

0 Raymond Lin over 1 year ago in reply to Ryu Yamashita

TI__Mastermind 34126 points

Hi Ryu-san,

Yes that is correct, if the cable current advertisement is greater than the minimum power configured for capability mismatch then CAP_MIS will not toggle.

Thanks and Regards,
Raymond Lin

0 Ryu Yamashita over 1 year ago in reply to Raymond Lin

Genius 3600 points

Hi Raymond,

Thanks for the reply.

I thought it would toggle, but you say this device does not toggle.
Am I correct in understanding that the TPS25730 can correctly recognize the current when USB-PD Negotiation occurs, but cannot recognize the current for Type-C specifications?

Sincerely,
Ryu

+1 Raymond Lin over 1 year ago in reply to Ryu Yamashita

TI__Mastermind 34126 points

Hi Ryu-san,

Apologies for the confusion, after further testing it's verified that CAP_MIS does not toggle for A-C cables, only for valid PD contracts. CAP_MIS is based on the power consumption calculated through the negotiated PDO voltage and current rating only (tied to PD protocol, not Type-C protocol).

Thanks and Regards,

Raymond Lin

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TPS25730: About power detection