PMIC MC34708 not coming up?

[ss12]

I am using PMIC MC34708 in one of the iMx537 design. The PMIC chip is not coming up.

I am giving 3.3V as the BP input. The reference voltages are coming correctly.

Any help in this regard is greatly appreciated. Thanks in advance.

[weidong_sun · Accepted solution]

Hello,Satyan,

     I have 2 suggestions about your design :

(1) BP Voltage.

    3.3V is too low. BP pin is for single battery input , It's normal input voltage should be 3.5~4.2V.

(2)WDI pin

    if MC34708 doesn't work, please measure WDI pin to check if this pin is High . If the level is low, MC34708 doesn't work.

Regards,

Weidong

[ss12]

Hi Weidong,

    Thanks for your reply. The said design is part of the bigger system and this is a module in it and has input power that is 3.3V only. I do not have any option to increase the voltage. Is there any other alternative chip available.

   WDI pin is showing low only.

    I have isolated all the loads from the chip completely to check if it was overloading. Now if I give 3.6V from an external source it tries to come up and goes down immediately.

    Is the load necessary for the PMIC to come up.

with best regards,

S.Satyan

[weidong_sun]

Hello,Satyan,

     The issue is not related to load . mc34708 is designed for single li-cell battery with standard 3.7V input, So for a single li-cell battery, it is MAX voltage is 4.2V, if you use 3.3V to be input of BATT pin on mc34708, It is really too low. We ofter use a 5v-->3.8v DC-DC power IC to be input of MC34708, this DC-DC is just like a signle li-cell battery !

Regards,

Weidong

[ss12]

Hi Weidong,

    Thanks for your reply. The chip is coming up now. I pulled the WDI to high. All the voltages are coming up even at 3.3V. :smileyhappy: Thanks for your support.

with best regards,

S.Satyan

[weidong_sun]

Hello,Satyan,

      Good Job !

      I still suggest you should notice the value of VCC_BP, 3.3V input is courageous design, You are a brave guy ! :smileyhappy: ,Hope you can use standard Voltage (3.7/3.8V) to be BATT input of MC34708 in other designs.
    

Regards,

Weidong