VP and VPH - Leave floating or ground?

[MarkRoy]

Hey Folks,

I'm working on a I.MX53 design.  We're not planning on making use of the SATA capabilities.  Should I ground VP and VPH on the I.mx53 or just leave them floating?   It's not clear from the datasheet or various guides available.

Cheers.

Mark Roy

[MarkRoy]

Great.  Thanks all for the advice.

Mark

[Yuri · Accepted solution]

General recommendations are as following :

If not using SATA interface and the embedded thermal sensor, the VP and VPH
should be grounded. 

Note, the I.MX53 SATA also integrates a temperature sensor. The temperature can
be read by the CPU, and frequency may be scaled-up or scaled-down accordingly.

In case the SATA, including the temperature sensor, is not needed :
- the VP and VPH should be grounded ;
- the rest of the ports both inputs and outputs could be left floating
(SATA_REFCLKM , SATA_REFCLKP , SATA_REXT , SATA_RXM , SATA_RXP , SATA_TXM)

When only temperature sensor is used:
- VP and VPH still need to be connected to 1.2V and 2.5V respectively.
- Reference clock input frequency is not important but needs to be within the
Specified range: 25Mhz to 156.25Mhz

[Yuri]

There are 3 options, based on SATA_ALT_CLK_REF fuse

'00' - 100MHz (External)

'01' - 50MHz (External)

'10' - 120MHz, internal (USB PHY)

'11' - Reserved

And It is recommended to work with internal USB PHY  (as workaround for ENGcm11851).

[Paul1z]

Hi Yuri,

Thank you for the quick response! We are looking at the SATA_ALT_CLK_REF fuse and noticed that it is in the FUSEBLOCK (not just a register setting, etc). We are using WEC7 with eBoot so we do not have access to the 'iim blow 4 3 4' command that uBoot allows, but we should be able to use something else. However, I would like to know more about the fuses. Is there a listing/document that describes all of the fuses in the FUSEBLOCK?

Thank You,

Paul

[Yuri]

Uboot can be loaded via the MFG tool and run as stand alone application.
If needed I can send it.

Also the IIM is described in the i.MX53 Reference Manual (RM), in particular, please
look at section  42.2.5 (Fuse Bank Operations).

Fuse map may be found in "Addendum to Rev. 2 of the i.MX53 Applications
Processor Reference Manual" - last chapters in recent RM on the Web.

[Paul1z]

Thank you! That addendum/document had the info.

[Paul1z]

Hi Yuri,

For the reference clock, this means having a clock connected externally to the SATA_REFCLKPiMX53, B14) and SATA_REFCLKM (iMX52, A14) pins, correct? The AN4380 document does say that I can also connect a clock from the USB PHY PLL - but this would also have to be externally, correct (Is this a pin on the iMX53)? The reason I am asking is because I managed to miss this section of the document and have only provided power to the SATA module (we only need termperature, not SATA functionality) with no external clock, so I am hoping we can somehow use/route a clock internally.

Thank You,

Paul

[DouglasAllen]

I grounded them. I don't remember the reasoning but I used zero ohm resistors in case I was wrong I could still float them.

Units work fine.

Doug