• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 62 subscribers
  • Views 286 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

BQ24075T: bq24075T Questions

Ian Wang
Mastermind 26495 points
Part Number: BQ24075T

Hi Sir,

Would  you pls help for bq24075T schematic questions as below? thanks.

VIN: VBUS_CHG(5V), from USB

VBAT: 560mA, 1C Li-ion Polymer Cell, typ. 3.7V max 4.2V

Input Current set: 600mA

Output Current set: 556mA

Q:

  1. EN2 connect to VBUS_CHG through 10Kohms, is it means input current from USB will control by ILIM?
  2. EN1 connect to GND through 100Kohms, is it make sense? 
  3. SYSOFF connect to GND through10Kohms, is it make sense if we will not disconnect VBAT?
  4. We will not use OUT, CE connect to GND through 10kohms is fine?
  5. For TMR pin, spec describe "6.25hour fast-charge safety timer", what means 6.25 hrs? Can we change 6.25hrs with others resistor value(d/s shows 46.4K)
  6. If not use PGOOD and CHG, need connect to GND or floating?是否能直接float?
  7. Input and Output capacitors have suggest value?
  8. OUT pin not used, connect it to GND through10uF, is it fine?
  9. TS pin,  VCOLD and VHOT 0.25 and 0.15 are fix value?(as below fig.)

0 and 50 degree is fixed value or it can change by customer? 

According NTC (10K, B value 3435)spec in 0 degree and 50 degree calculate as below formula, 19.6K and 8.66K are make sense?

Thanks, Ian.

  • 0
    TI__Mastermind 23220 points

    Hi Ian,

    To answer your questions:

    EN2 connect to VBUS_CHG through 10Kohms, is it means input current from USB will control by ILIM? EN1 connect to GND through 100Kohms, is it make sense? 

    Yes, this will configure the device to have the input current limit as set by the ILIM resistor. It looks like the calculations have already been done and are correct.

    SYSOFF connect to GND through10Kohms, is it make sense if we will not disconnect VBAT?

    Yes, this is fine. Pulling SYSOFF low will keep the battery connected to the system for normal operation

    We will not use OUT, CE connect to GND through 10kohms is fine?

    There is a need to have a capacitor at the output. The CE pin can be connected to GND directly if there is a desire to reduce the amount of components.

    For TMR pin, spec describe "6.25hour fast-charge safety timer", what means 6.25 hrs? Can we change 6.25hrs with others resistor value(d/s shows 46.4K)

    Yes, the safety timers can be programmed with a resistor in the 18-kOhm to 72-kOhm range. The following information in the data sheet can be used to program the timers.



    If a 6.25 hour fast charge safety timer is desired, the calculated resistor value is 50k. I will look comment this on our data sheet for future changes.

    If not use PGOOD and CHG, need connect to GND or floating?是否能直接float?

    Leaving this pins floating should be fine. I will check and update if I see there is an issue with leaving this floating

    Input and Output capacitors have suggest value?

    Yes, for the input, we recommend a capacitor in the range of 1-uF to 10-uF. For the output, we recommend a 4.7-uF to 47-uF capacitor.

    Looking at the schematic, I see no issues there.

    OUT pin not used, connect it to GND through10uF, is it fine?

    Yes, if not using the OUT pin, connecting the OUT pin to GND through a 10uF capacitor is fine.

    TS pin,  VCOLD and VHOT 0.25 and 0.15 are fix value?(as below fig.)

    Yes, these thresholds are fixed.

    0 and 50 degree is fixed value or it can be changed by customer?

    This can be changed by adding resistor as shown:

    Depending on the NTC and the desired temperature, the NTC calculator can be used to calculated the recommended R6 and R7 resistor.

    It looks like the NTC calculator has already been done.

    Schematic Review

    Everything looks fine. I’ve double checked the numbers for resistor calculations shown on the schematic and only the TMR calculation may be incorrect if the 6.25 hour is desired.