BQ21040: Pre-charge to fast-charge transition threshold

Hi Stefan,

Please provide more information to diagnose this issue. Please share a schematic. What is VIN, VOUT, TS, and CHG/ voltage? Please capture a waveform of the previous four waveforms as well.

Regards,

Mike Emanuel

Hi Michael,

schematic attached as as the waveforms (1c charging at 3.8V battery voltage, 1x without connected battery)

V_BAT_3.8V.pdfV_BAT_open.pdf

Hello Stefan,

Please describe how you are measuring this transition. Also, please label the provided waveforms. I need to verify which channel is which.

Regards,

Mike Emanuel

Hi Mike,

In accordance with the circuit diagram, 5V is applied to V_USBC. In the PDF V_BAT_open, nothing is connected to V_BAT; in V_BAT_3.8V, a battery with 3.8V cell voltage is connected to V_BAT. Vin = blue, Vout = red, TS = green and nCHG = yellow.

BR,
Stefan

Hi Stefan,

I am missing the piece about "a Pre-charge to fast-charge transition threshold of 1.54V instead of the 2.5V." How are you observing this?

Regards,

Mike Emanuel

HI Mike,

For this test, customer used a four-quadrant power supply (Rohde&Schwarz NGM201) as battery and simulate the charging cycle with it. The charging current switches from Iprecharge to Ifastcharge at 1.51V.

BR,
Stefan

Hi Stefan,

Where is the battery voltage 1.51 V being measured?

Regards,

Mike Emanuel

Hi Mike,

the voltage was set directly on the four-quadrant power supply unit (which was used as a battery simulation).

BR,
Stefan

Hi Mike,

customer measured directly at Vout pin. so this is not the issue.

BR,
Stefan

Hi Stefan,

We are checking and will get back to you in a day or two.

Thanks a lot,

Ning.

Hi Stefan,

I need a clear image of VIN, VOUT, IOUT, and TS before, during, and after this transition occurs. Please measure all these voltages at the pin. Also, have you tried an ABA swap? In other words, take off the existing unit and place it on the old board. Place a new or known good unit on the existing board.

Regards,

Mike Emanuel

Hi Mike,

I repeated the measurement today. Nothing changes in the Vin, Vout and TS signals during the changeover (short-term and long-term). I recorded Vin, Vout, and TS during the switch (trigger point). Vout was set from 1.3V to 1.4V to trigger the switch from precharge to FastCharge. I also recorded a log with the charging current over the entire battery voltage range (resolution 100 ms). Here it is clear that the IC switches from PreCharging to FastCharging at 1.4V. Then at 1.7V the IC switches back briefly to PreCharging (this is exited after about 300 ms). It then remains with FastCharging. 

BR,
Stefan

pico1.pdflogfile.csv