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Original question:

BQ25798: BQ25798

BQ25798: REGN NOT GENERATING

Saira Shaikh
Prodigy 170 points
Part Number: BQ25798

Tool/software:

Hi all!

I am using BQ25798 Battery Charger IC 

In the IC, when I use the Battery, desired output is being received at SYS Pin.

However, when I keep the battery connected and connect VBUS1, via the ACFET-RBFET Circuitry, to Input voltage 12V ( Greater than V_BAT), REGN is not generating. Additionally, there is no current being drawn from Power supply. 

I am getting the following values. Please suggest some solutions:

1. VAC1= 12V

2. VAC2 = 12V 

2. ACDRV1=17V 

3. VBUS1 = VBUS2 = 12V

4. REGN=0.017V

5. SYS=10.76V (Same as Battery Voltage)

Kind Regards.

  • 0
    TI__Guru**** 166626 points

    HI Shaikh,

    Can you provide your schematic?  Is ILIM_HIZ pin ground by chance?

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 170 points

    Hi Jeff, 

    I have attached the schematic above. The ILIM_HIZ Pin is not ground. Can you please point me towards the issue? 


    Kind Regards.

  • 0 in reply to Saira Shaikh
    TI__Guru**** 166626 points

    Hi Shaikh,

    REGN is powered from PMID voltage.  When VBUS is applied, the FET between VBUS and PMID turns on. 

    If there is a voltage on PMID (can you measure with DMM?) and not REGN, then the charger is in HiZ mode.  HiZ mode can be forced by taking ILIM_HIZ pin low or host I2C write setting EN_HIZ bit = 1.  With battery attached, the only way for charger to auto set EN_HIZ bit high to protect itself is if it measures inductor current >10A. What are you load and system current levels?  With a 3.3A inductor, ICHG + ISYS must be slightly less than 3.3A or the inductor will saturate and current spikes could reach 10A.

    If there is voltage on VBUS and not on PMID, then the FET between VBUS and PMID is damaged, possibly due to hot plug ringing of the 12V supply > 30V abs max.

    Regards,

    Jeff