• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 247 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

BQ25570: not charging V-Bat when V_inDC is greater than the output voltage

BQ25570: VIN(DC) < VBAT_OV : is this VIN(DC) OCV or after MPPT adjustment (i.e. 80% or 50% of VIN OCV)

Sami Karjalainen
Prodigy 50 points
Part Number: BQ25570

Hi,

As per the title, the BQ25570 datasheet specifies that VIN must be ~400mV less than VBAT_OV in order for charging to occur.

Two questions;

1) For the VDELTA formula = VBAT_OV - VIN(DC); is VIN(DC) the open-circuit voltage OR the voltage after MPPT factor applied (i.e 50% to 80% of open-circuit voltage) of the DC source (aka solar panel) ?

    Our device operates from a solar panel with open-circuit voltage of up to 5.5V, and our LPF battery will have a VBAT_OV of ~3.6V. We are wondering if we can configure the MPPT to 50% to allow charging an LFP battery up to 3.6V from a solar panel with OCV of 5.5V.

2) If we cannot use MPPT regulated voltage to get VIN(DC) < VBAT_OV, can we instead place an LDO (say 3.3V) in series between the solar panel and the VIN(DC) pin on the BQ25570 (such that the VIN(DC) OCV seen by BQ25570 is less than our configured VBAT_OV of 3.6V).

Regards,

Sam

  • 0
    TI__Guru**** 165776 points

    Hi Sam,

    Regarding 1, it is VIN(DC)=VMPPT for VDELTA.

    Regarding 2, in theory yes but the LDO will likely collapse the solar panel unless it has an MPPT function.  If your LFP battery maximum charge current is up to 110mA, I recommend you place it at the output of the buck converter, set for 3.6V regulation.

    Regards,

    Jeff