i.MX6 USB charger detector with a dead battery

[paulmerana]

Hello

We are looking to design an i.mx6 Solo or Dual Lite battery powered i.mx6 device which charges from USB which will meet the USB Battery Charging Specification. We currently have a charger which will interface with the i.mx6 charger detector USB_CHG_DET# line such that when this line is low there is a USB charger attached to the system rather than a SDP USB port. We were made aware of errata ERR006281 concerning the charger detector in the i.mx6 where as it requires VDDHIGH_IN to be powered up for the charger detector to operate. For our system to draw less than 100mA I can not turn on the PMIC / i.mx6. If we are plugged into a DCP we can boot right up however we must be able to detect that we are indeed plugged into a charger. If we are plugged into a SDP and if the battery has sufficient charge we can limit the input current to 100mA and power on the i.mx6 to allow it to enumerate and attempt to negotiate for a higher current limit. The problem is if the battery is dead or very low it can not do this.

1) VDDHIGH_IN is the input which feeds VDDHIGH_CAP. This power rail also powers NVCC_LVDS2P5, NVCC_RGMII, NVCC_MIPI. Are these rails safe to be powered up along with VBUS while no other i.mx6 rails are powered up?

2) What is NXPs solution for a USB/Battery powered device to pass dead battery provisioning? Is there a reference design?

3) What is NXPs recommended hook up scheme for VDDHIGH_IN to allow the system to detect the charger on power up without the rest of the i.mx6 from being powered on?

4) Currently in our system if the battery is not dead so vsys is already on and the USB is plugged in the system does not boot up without the ON/OFF button being pressed. Is there a way to make this automatic? (Power on USB VBUS detection)

Thank you

[CarlosCasillas]

Hi,

Regarding question 1, there is no issue having powered the mentioned power rails without the others.

Regarding additional questions, you could take a look at the SABRE platform for i.MX53 (RDIMX53SABRETAB), which includes a battery, with USB charger capabilities:

On the Software & Tools section, you could find the schematics, refer to page 9 for additional reference.

Besides, you could also take a look at BC3770 part:
http://www.nxp.com/docs/en/data-sheet/MC32BC3770.pdf

Hope this will be useful for you.
Best regards!
/Carlos
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[paulmerana]

Thank you for the reply.

The imx 53 tablet is powered by a battery or 15v. The USB OTG does not charge the battery. We are trying to do USB charging of the battery and running of the system. I do not even see a charger detector IO line on the i.mx 53, does it have one?

The design started with the BC3770 however there were some problems. It would be a good part however it does not hook up to the charger detector in the i.mx6 and relies on I2C commands to set the current limit. With a dead battery the input current would be set to 500mA until SW turns it down the input current would be 500mA. If you power up your system and it draws over 100mA before USB enumeration (not inrush) would this not be a violation of the USB battery charging specification? Additionally the package on the BC3770 causes problems for assembly and drives up the board cost due to the vias necessary for the package.

What can I expect the output of the charger detection to do on the i.mx6 on USB power up? Will it show the system is hooked up to a charger or a SDP? (Low or pulled high with the resistor) until VDDHIGH_IN is powered up?