Reset loop, DCDC_BATT source only 3.3V

[peterbärtsch]

Hello

We supply our borad over the DCDC_BATT Pin with 3.3V (from DCDC). We use following configuration:

When the borad powerd with 3.3V we have a reset during the barebox is starting. We can increase the FRAC_CPUFRC to 28 or HBUS_DIV to 8 and the Linux starts normally.

When we power our board with 3.8V we have no problems. The Linux starts with the fastest clock configuartion.

Vbat and VCC_Logik (confusing name I now) are connected. What is the problem?

Best regards

Peter

[Yuri]

According to footnote of Table 8 (Recommended Power Supply Operating Conditions)
of the i.MX28 Datasheet(s) :
"With external loadings (for example, one DDR2 device and SD Card/NAND Flash),
MX28 PMU was tested at BATT/DCDC_BATT > 3.30 V".

So, BATT/DCDC_BATT > 3.30 may be recommended.

Have a great day,
Yuri

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[peterbärtsch]

Hello

Denotes the DCDC_BATT is for 3.3V supply unusable?

Best regards

Peter

[Yuri]

In the case, the issue may be caused because of really high (external) load.
Also, special software configuration should be applied here ; please take a look at
section 4.1.1.2 (DCDC_BATT source only: software configuration)  of the app note AN4199.

http://cache.freescale.com/files/32bit/doc/app_note/AN4199.pdf

~Yuri.

[peterbärtsch]

We supply only a NAND Flash and DDR2 Memory on 1.8V over the imx. I check the consumption.

Best regards

Peter

[Yuri]

  Peter, good day !:

Is it possible for test purposes to power DDR2 separately (from an external source)?

~Yuri.

[peterbärtsch]

Hello Yuri

I measured the 1.8V path and de current was about 235mA...  And thats probable to mutch.

We use:

Flash:  SPANSION S34MS01G100BHI000

RAM:  SAMSUNG K4T1G164QF--BCE6000

Peter

[Yuri · Accepted solution]

Yes, You may look at Table 13 (Power Supply Characteristics) of the Datasheet
(IMX28CEC, Rev. 3, 07/2012) :
DCDC_VDDA Maximum Output Current (VDDA = 1.8 V)  = 200 mA

~Yuri.