i.MX6SDL power supply on the time change LDO enable or bypassed mode.

[satoshishimoda]

Hi community,

Our partner have some questions about i.MX6SDL.

Please see Table 9 in IMX6SDLCEC Rev.3, and please see their questions as below.

[Q1]

If change i.MX6SDL from LDO enabled up to 996Mhz -> LDO bypassed up to 966MHz, PMIC output cannot satisfy i.MX6SDL operating range because there is no overlap between the operating range of these two modes.

So we guess if we want to change from LDO enable to LDO bypassed, we should do the following procedure.

Is this correct?

1. Change PMIC output from LDO enabled up to 996MHz -> LDO enabled up to 792MHz.

2. Change i.MX6 from LDO enabled to LDO bypassed.

[Q2]

Can we use the following procedure to change i.MX6 from LDO enabled to bypassed even though PMIC output over the operating range of LDO bypassed for just a moment?

1. Change PMCI output from LDO enabled up to 996MHz -> LDO bypassed up to 996Hz.

2. Change i.MX6 from LDO enabled to LDO bypassed.

[Q3]

PMIC output for VDD_SOC_IN will be out of operating range on the time change from i.MX6 LDO enabled to LDO bypassed.

It is not avoidable because operating range of VDD_SOC_IN is not changed by CPU frequency.

Is the out of operating range no proglem on the time changing LDO mode?

Best Regards,

Satoshi Shimoda

[igorpadykov · Accepted solution]

Hi Satoshi

1. yes, in general procedure is correct:

Change core frequency down to 792MHz

Change PMIC output from LDO enabled up to 996MHz -> LDO enabled up to 792MHz.

Change i.MX6 from LDO enabled to LDO bypassed.

Change core frequency up to 996MHz

2.3. formal answer no: ecxeeding datasheet figures is not allowed and may affect device reliabilty.

Best regards

igor

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[satoshishimoda]

Hi igor,

Thank you for your reply.

> 1,2

OK, I understood.

>3

Yes, we want to follow the datasheet if we can.

In case of i.MX6DQ, we can follow the datasheet because LDO enabled and LDO bypassed have same voltage range for VDD_SOC_IN (1.275V - 1.3V).

However, in case of i.MX6SDL, LDO enabled and LDO bypassed have other voltage range completely (enabled : 1.275V - 1.5V, bypassed : 1.15V - 1.225V).

So it is not avoidable becoming the voltage out of the range which written in datasheet on the time switching LDO enabled <-> LDO bypassed.

How should we care this issue?

Best Regards,

Satoshi Shimoda

[igorpadykov]

Hi Satoshi

for such cases one needs to change cpu frequency before changing its

voltage, to conform datasheet requirements

Change core frequency down to 792MHz

Change PMIC output from LDO enabled up to 996MHz -> LDO enabled up to 792MHz.

Change i.MX6 from LDO enabled to LDO bypassed.

Change core frequency up to 996MHz

Best regards

igor

[satoshishimoda]

Hi igor,

According to i.MX6SDL datasheet (IMX6SDLCEC Rev.3), VDD_SOC_IN voltage range is not changed by cpu frequency.

So PMIC output voltage for VDD_SOC_IN will be out of range on the time changing from LDO enabled mode to LDO bypassed mode even if user follow the below sequence.

Change core frequency down to 792MHz

Change PMIC output from LDO enabled up to 996MHz -> LDO enabled up to 792MHz.

Change i.MX6 from LDO enabled to LDO bypassed.

Change core frequency up to 996MHz

Or it is allowable even though VDD_SOC_IN is out of range if user follow the above sequence?

Best Regards,

Satoshi Shimoda

[igorpadykov]

Hi Satoshi

yes I think it is allowable according to its implementation below

ENGR00276023-1: ARM: imx: add ldo bypass

https://gitorious.org/u-mobo/uboot-imx/commit/7bb604fa058b253045002458d20c8e75655af91b

Best regards

igor