TUSB8042A: Pin Strappping at FULLPWRMGMTz/FULL AUTOz/SMBA1/SS_UP \ Pin#40

Marion Loessl

Part Number: TUSB8042A

Hi,

my customer has a question regarding pinstrapping at piin #40 at TUSB8042A:

Does "I/O , PD" mean, that a pull down is integrated?

If that is the case, then without external circuit, a "Low" signal is read, correct? If it is a low signal, "0 = Power switching and over current inputs support" and the Powermgmgt features are turned on. That would be our understanding.

BUT, further down it says "Can be left unconnected if full power management and SMBus are not implemented.“ that is the exact opposite of the above thinking, because by default, SMBUS and Powermgmgt would be deactivated.

So, is a pull down necessary to activeate the Power Mgmt feature or not?

Kind regards,

Marion

over 5 years ago

0 Brian Zhou over 5 years ago

TI__Guru*** 146515 points

you are right, It seems mistake in datasheet for this comment "Can be left unconnected if full power management and SMBus are not implemented.“

0 Marion Loessl over 5 years ago in reply to Brian Zhou

TI__Expert 3705 points

Hi Brian,

alright, so will that be corrected?

My customer doesn't want to use the PWRCTL Pins. So strapping or not?

Kind regards,

Marion

0 Marion Loessl over 5 years ago in reply to Brian Zhou

TI__Expert 3705 points

I need more detailed information

0 Brian Zhou over 5 years ago in reply to Marion Loessl

TI__Guru*** 146515 points

sure, we will update datasheet.

so you want to use power management but don't want to use PWRCTL pin?

0 Marion Loessl over 5 years ago in reply to Brian Zhou

TI__Expert 3705 points

At the customer application, those pins a not used, but the signals of the overcurrent event. Here the signals of 2 USB ports are summed and brought to the CPU ((ort 0+1, Port 2+3, …).

0 JMMN over 5 years ago in reply to Marion Loessl

TI__Guru 60870 points

Hi Marion,

If the PWRCTL pins are not used to control downstream port power then FULLPWRMGMTz should be = 1 (not asserted). Overcurrent reporting is a USB requirement regardless of full power management or not.

Regards,

JMMN

0 Marion Loessl over 5 years ago in reply to JMMN

TI__Expert 3705 points

Hi JMMN,

so that mean, in the descripted application, we can leave the pins unconnected?

The internal Pull down is in place?

Kind regards,

Marion

0 JMMN over 5 years ago in reply to Marion Loessl

TI__Guru 60870 points

Yes, there is an internal pulldown so FULLPWRMGMTz = 0, asserted. Full power management reporting is enabled by default.

Regards,

JMMN

0 Marion Loessl over 5 years ago in reply to JMMN

TI__Expert 3705 points

Hi JMMN,

okay, I understand then, that we should add pin strapping, correct?

Kind regards,

Marion

0 JMMN over 5 years ago in reply to Marion Loessl

TI__Guru 60870 points

If power switches are not implemented in the application, then a pull-up should be installed on FULLPWRMGMTz.

Regards,

JMMN

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TUSB8042A: Pin Strappping at FULLPWRMGMTz/FULL AUTOz/SMBA1/SS_UP \ Pin#40