• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 466 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.

BQ25703A: About Precharge and Fast charge switching conditions

Tsukui Yusuke
Guru 21930 points
Part Number: BQ25703A

Hi,

Could you tell me about Precharge and Fastcharge switching?
(4cell battery and EN_LDO is valid condition.)

1.ChargerStatus does not become Precharge even if the ADCVSYSBAT falls below MinSystemVoltage (11776mV setting).
   BQ25703A does not use ADCVSYSVBAT voltage to switch between Precharge and Fast charge.
   Is this understanding correct?
   If so, Could you tell me the detection method and threshold of BATTERY LOWV COMPARATOR?　

2.Using the voltage information of the gauge in place of the ADCVSYSBAT.
　In that case, BQ25703A switched to Precharge near MinSystemVoltag.
　However, it took a while for Charge status to switch to Precharge.
　Could you tell me the timing condition that bq25703A reflects ChargerStatus?

Best regards,
Yusuke

  • 0
    TI__Mastermind 32745 points

    Hi, Yusuke,

    1. BQ25703A measures the battery voltage through SRN pin and uses a hysteresis comparator to decide Precharge or Fastcharge. For example, when the 1S battery voltage is lower than 2.8V, it is in Precharge; when the 1S battery voltage is higher than 3.0V, it is in Fastcharge. There is a 200mV hysteresis in the battery lowv comparator. See below spec excerpted from the datasheet. 

    2. Since the battery fuel gauge IC has a dedicated/separate control on Precharge, it makes its own control on the charge mode. There may be a time difference. Regarding the BQ25703A status refresh. It is instantaneous without further delay. 

  • 0 in reply to Tiger Zhou
    Guru 21930 points

    Hi Tiger,

    Thank you for your response and support.
    Let me ask you about your answer and explanation.

    〉1. BQ25703A measures the battery voltage through SRN pin and uses a hysteresis comparator to decide Precharge or Fastcharge. For example, when the 1S battery voltage is lower than 2.8V, it is in Precharge;
    〉when the 1S battery voltage is higher than 3.0V, it is in Fastcharge. There is a 200mV hysteresis in the battery lowv comparator. See below spec excerpted from the datasheet. 

    Could you tell me ”VBATLV_FALL, VBATLV_RISE, VBATLV_RHYST" for 4cell?
    Customer has set the MinSystem Voltage Register to 11776mV.
    Customer wants to know ”VBATLV_FALL, VBATLV_RISE, VBATLV_RHYST" corresponding to "MinSystemVoltage".

    Best regards,
    Yusuke

  • 0 in reply to Tsukui Yusuke
    TI__Mastermind 32745 points

    You can scale up for 4S by multiplying x4. 

  • 0 in reply to Tiger Zhou
    Guru 21930 points

    Hi Tiger,

    Thank you for your support.
    I understand the your explanation.

    Customers want to know the details of switching between Precharge and Fastcharge for strict charge control.

    １．For 4cell, is the following understanding correct?
    ・BATLOWV falling threshold： 11.2 V 
    ・BATLOWV risign threshold：12 V
    ・BATLOWV hysteresis：200mV

    ２．Could you tell me the maximum and minimum values of ”BATLOWV falling threshold" "BATLOWV risign threshold" "BATLOWV hysteresis"?

    ３．In LDO Mode Enable, does MinSystemVoltage setting affect the comparator threshold?
    　　Following contents are described in the data sheet.
           For example, if the MinSystemVoltage setting is 15V, Which setting has priority?

           

    Apologies for my continuous post.

    Regards,
    Yusuke

  • 0 in reply to Tsukui Yusuke
    TI__Mastermind 32745 points

    1. BATLOWV falling threshold： 11.2 V 
    ・BATLOWV rising threshold：12 V
    ・BATLOWV hysteresis：800mV

    2. There is no distribution data. 

    3. Min system voltage won't affect the comparator threshold. The BATLOWV comparator is fixed in the part. When EN_LDO is ON, the charge current will be clamped when battery voltage is below the Min system voltage. I don't think there is a conflict. Both will be effective as described. In this case, the EN_LDO extends the pre-charge current to Min system voltage. 

    Hope this clarifies your question.