iMX28 power supply, question about current

[victorien]

Hi,

I have a question about iMX28 power part :

I use the internal power supply and battery charger. It's works pretty well but I see that when 5V input Voltage decrease, the current used by 5V input. Is there a system on imx28 which control this current ?

Thanks.

[jamesbone]

Hello Victorien,

I apologize but I think I do not understand your question,  let me see if this is the issue when 5V Input Voltage Decrease, the  Current of the 5V Input it is also decreasing? or you mean  it is Increasing? Can you please clarify?

[victorien]

Sorry, I forgot some words...

When 5V input voltage decrease, the current of 5V input also decreased.

[jamesbone]

Hello Victorien,

I believe you are experiencing, the same behavior from this thread :

i.MX28 Detect voltage stabilization

In i.MX28 L2.6.35_1.1.0_130130 release, you can configure the power source.

In the MX28_EVK_Linux_User_Guide.pdf,

2.7 Configuring Power Source

This release adds power source configuration to enhance the performance of the system that has only VDD 5V or only battery. If the build is configured for VDD 5V only, the system will not power on if the system has battery but does not have VDD 5V.

To configure the power source, NO_DCDC_BATT_SOURCE and NO_VDD5V_SOURCE can be defined in power_prep.c of i.MX28 bootlet. The steps to configure the power source are as follows:

1. Generate the bootlet source code:

./ltib –p boot_stream.spec -m prep // generate bootlet source code

2. In imx-bootlets-src-10.12.01/power_prep/power_prep.c:

#define NO_DCDC_BATT_SOURCE // enable VDD 5V only

Or,

#define NO_VDD5V_SOURCE //enable battery-only

3. Build the bootlet code:

./ltib -p boot_stream.spec -f //build bootlet code

If NO_VDD5V_SOURCE or  NO_DCDC_BATT_SOURCE is defined.  Battery charging is disabled and transition between power sources is disabled.

You can reference AN4199 "Using the i.MX28 Power Management Unit and Battery Charger".

[victorien]

Hello,

Unfortunatly it's not the same issue. And I'm not that what I see is really an issue.

Usually on battery charger chip there is a current limiter which reduce the current when the input voltage decrease ; this system protect the power supply. I wonder if there is the same system in iMX28 power part.