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BQ25616: Questions for BQ25616

Oliver Lin
Expert 3255 points
Part Number: BQ25616

Hi team,

My customer has some question on the usage of BQ25616, please see the questions below.

1.  What is the relation between these two parameters?

Customer concerns that if we have K value as 715 (Axohm), Does the fast charge current regulation accuracy change due to K value close to Max or min value? Because this might affect the max charging current setting. 

2. From datasheet page 19, how to set it as "Set by ILim pin" for all time. how to connect D+/D- to achieve this?

3. From datasheet mentioned VBUS rising without battery, my customer concerns that what if VBAT(4V) connected, when will charger start charging? It looks like charger is acting as a boost.

  • 0
    Prodigy 10 points

    For additional information about question 3, CE PIN always short to gnd and external ACFET is removed.

  • 0 in reply to TING CHAO LIN
    TI__Mastermind 49211 points

    Hi,

    1.The Kichg spec shown on the d/s has a variation of around +/-5.6%.

    The fast charge accuracy @ Richg=1100ohm shown on the d/s has a variation of around +/-16%,

    The fast charge accuracy @ Richg=562ohm shown on the d/s has a variation of around +/-6%,

    The fast charge accuracy @ Richg=372ohm shown on the d/s has a variation of around -6% - +4%.

    Kichg does not tell the fast charge current accuracy.

    2.When D+/D- pins are open, the input current limit is set by ILIM pin.

    3.Referring to 9.3.1 Power-On-Reset (POR) on the d/s, When VVBUS rises above VVBUS_UVLOZ or VBAT rises above VBAT_UVLOZ, the sleep comparator, battery depletion comparator, and BATFET driver are active.

    Referring to 9.3.3 Power Up From Input Source on the d/s, the charger starts charging in step 6. Power Up Converter, see Section 9.3.3.6. Please refer to Figure 10-3. Power-Up with Charge Enabled for the related waveforms.

    Thank you very much,

    Ning.

  • 0 in reply to Ning T
    TI__Expert 3255 points

    Hi Ning,

    Thank you for your input.

    Customer got some following questions

    1. If those are not related, if the Kich follow Eq1 to set, but Kich has tolerance from 639~715. Do we need to consider this ? If we want to set max ichg as 0.83A. What Kichg should be applied to get Richg?

    2. Customer's battery pack has no gauge, if the cell due to JEITA spec that requires ichg can not be higher than 0.83A. But the calculated value from Eq1 is 1A. Do we need to change the ichg into 0.83A to fit JEITA?

    3. Could you please share some explanation what sleep mode is? I am not able to find it from datasheet. What will BQ25616 behave once under sleep mode?

    Thanks,

    Oliver

  • 0 in reply to Oliver Lin
    TI__Mastermind 49211 points

    Oliver,

    We are working on it and will get back to you.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    TI__Mastermind 49211 points

    Oliver,

    1. ICHG=KICHG/RICHG, KICHG typical (677) determine the typical ICHG value. For the fast charge accuracy, please refer to the fast charge accuracy specs listed on the d/s. In general, the accuracy gets better for higher fast charge current setting.

    2. Referring to 9.3.7.4.1 JEITA Guideline Compliance During Charging Mode (BQ25616J), At cool temperature (T1-T2), per JEITA  the charge current is reduced to 20% of ICHG (at normal temperature) automatically and the controller suspends charging if the temperature is below T1. Figure 9-6. JEITA Profile (BQ25616J) shows the details. 

    3. Sleep mode refers to below

    In buck mode, if VVBUS < VBAT + VSLEEPZ

    In boost mode, if VVBUS > VBAT + VSLEEPZ

    In sleep mode, REGN LDO turns off. The battery powers up the system.

     

    Thanks, 

    Ning.

  • 0 in reply to Ning T
    TI__Expert 3255 points

    Hi Ning,

    1. If we are using typical value, how about the max and min value difference from typical value not being considered? 

    2. Customer is using BQ25616, non-J version. From the behavior you mentioned, the charging current has been affected by actual room temperature, not normal temperature operating current anymore. Is my understanding correct?

    3. About sleep mode, it looks like charger will not behave any switching, Battery will power up system from BATFET, is that correct? 

  • 0 in reply to Oliver Lin
    TI__Mastermind 49211 points

    Oliver,

    We will get back to you on the next business day.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    TI__Mastermind 49211 points

    Oliver,

    1. KICHG min/max is not directly related to the fast charge accuracy. For the fast charge accuracy, please refer to the fast charge accuracy specs listed on the d/s. In general, the accuracy gets better for higher fast charge current setting.

    3. Yes.

    Thanks,

    Ning.