Question, i.MX28 ENABLE_DCDC bit setting

[Aemj]

Dear team,

I would like to ask about ENABLE_DCDC bit setting of i.MX28.

My customer is confused on the setting of ENABLE_DCDC bits.

There are two ENABLE_DCDC bits;

One is in HW_POWER_5VCTRL register and another is in HW_POWER_DCDC4P2 register.

In i.MX28 reference manual, it is said as follows for the description of the bit in HW_POWER_DCDC4P2 register.

“Enable the dcdc converter to use the DCDC_4P2 pin as a power source…”

In my understanding the DCDC_4P2 comes from internal 4P2 LinReg. And it also means 5V is present as reference manual says as the description for the bit in HW_POWER_5VCTRL.

So, the customer thinks the meanings of two ENABLE_DCDC bits are the same.

Could you give a help to better understanding on the two ENABLE_DCDC bits setting?

Thanks,

Miyamoto

[Yuri · Accepted solution]

The DCDC converter has two power sources :

  1) VDD5V via the VDD4P2  ;

  2) DCDC_BATT input.

  HW_POWER_DCDC4P2[ENABLE_DCDC] serves to select the source of the

DCDC converter : DCDC_4P2 or DCDC_BATT.

  HW_POWER_5VCTRL  bit will cause the DCDC converter

to remain on after 5V (VDD5V) is connected in order to guarantee

stable supply voltage. Please take a look at section 11.3.2.1 (Battery

Power to 5-V Power ) of the i.MX28 Reference Manual.

Have a great day,
Yuri

-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------