i.MX28 EVK board boot up without DCDC block

[JHY]

Hi all, I want to MX28 without DCDC block and tested it in MX28 EVK.

But it was fail to upload u-boot, so Is there an guide for using for not DCDC but linear regulator?

I edit SPL code and memory tests in SPL has no problem. The last register of power block is below.

5vctrl (2403F592),

dcdc4p2(A000001F),

vddd   (00F00710),

vdda   (000F070C),

vddio  (00070406),

vddmem (00000330)

sts    (2133AA2E),

power_charge(00400000)

hw_power_ctrl(0021AA80)

Thank you.

[igorpadykov · Accepted solution]

Hi JHY

please check below documents which describe this configuration:

Application note sharing: Issues often met in i.MX28 application

AN4199 Using the i.MX28 Power Management Unit

L2.6.35_10.12_5V_SUPPLY_PATCH : Linux patch for i.MX28 SDK 2010.12 to add the most

robust support possible for a VDD5V or DCDC_BATT only configuration..

L2.6.35_1.1.0_ER_SOURCE : i.MX28 Linux 2.6.35 Source Code Files and documentation.

Best regards

igor

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[suhask]

Thank you for uploading the patches.

These patches are for configuring the board with either DCDC_BATT or VDD5V.

Either way it selects one of the sources, switches on the 4p2 linreg and then feeds the DC-DC switching converter.

It does not switch off the DC-DC converter.

Is there any way by which we can run the board without switching to the DC-DC converter?

That is through the daisy chained linear regulators?

[igorpadykov]

one can look at attached appnote.

~igor

[suhask]

We already went through the app note.

In section 2.1, towards the end of section, it is said that

"LinRegs should only be used to power the rails during boot up when the 4.2 V LinReg is not initialized."

And that is what we see in the u-boot spl code too.

Our application is supplied with 5V from a wall adapter.

In the app note in section 3.1.2 it is said that

"When a 5 V supply is detected, the internal LinRegs powers ON the i.MX28 processor. The power rails
are raised to their default values and the ROM begins to process. When the i.MX28 processor is booted,
the device enables the 4.2 V LinReg to supply power to the DC-DC converter instead of using the internal
LinRegs to power the rails."

Is it possible to change this process and continue booting with the LinRegs?

We are looking for a power up sequence excluding the DC-DC converter.

[igorpadykov]

>Is it possible to change this process and continue booting with the LinRegs?
>We are looking for a power up sequence excluding the DC-DC converter.

in general yes, one can continue booting with the LinRegs, just remove DC-DC codes.

[suhask]

Went through datasheet and commented out DC-DC related code and configured for Linreg only boot.

Now the board tries to bootup. Initialises RAM and after setup_reloc(), probably when it tries to access ram, the voltage on 1.8V rail (RAM is connected in this) dips by 0.73 volts and board hangs.

Last of the logs are as given below

RAM Configuration:
Bank #0: 40000000 128 MiB

DRAM:  128 MiB
initcall: 40015c38
New Stack Pointer is: 47b0fee0
initcall: 40015e28
initcall: 40015f68
initcall: 40015db8
Relocation Offset is: 07f12000
Relocating to 47f14000, new gd at 47b0ff08, sp at 47b0fee0

What may be the reason for this happening?

[igorpadykov]

seems current providing by LinRegs is not sufficient for running from

ddr. For that it is necessary to use DC-DC providing more current.

Processor designed to use DC-DC for normal operation, LinRegs

are used only for start up and initializing ddr memory.

Best regards
igor

[suhask]

We are stuck in a similar issue where we are facing interference from the switching regulator with our 433Mhz radio.

We tried changing the switching frequencies to the recommended values (19,20,24) but it did not help.

We are thinking to move to a VDD5V only configuration. The patch file linked in the above post will prove helpful to us.

But this link is broken. Can you re upload "Linux patch for i.MX28 SDK 2010.12 to add the most robust support possible for a VDD5V or DCDC_BATT only configuration.." file?

Or share any pointers in this direction?

Any help will be greatly appreciated!