• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 653 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.

BQ24170: BQ24170 input has 20hz noise

Star Xu
Genius 9645 points
Part Number: BQ24170
Other Parts Discussed in Thread: BQ24172

Hi

BQ24170 is used as charge management IC, and 12V digital power supply is used as input. The power source ground and chip's ground are connected by a 0R resistance. After power on, noise of about 20hz is generated on the input side of 12V, which affects VBAT and SYSTEMOUT ( VOUT output).

Attached schematic 

Input waveform

VBAT detect waveform

System output waveform

Please give some suggestions

Thanks

Star 

  • 0
    TI__Guru**** 166176 points

    Hi Star,

    Your e2e post says BQ24170 but the schematic says BQ24172.  If BQ24172, CELLS pin becomes FB and it cannot be shorted to ground as shown in the schematic.  Also, the BTST cap, C7) is too large.  We have only tested with 0.047uF.  D1 isn't needed for reverse blocking if you have Q1 and Q2. 

    If battery is not connected but input power is connect, the BATFET should not be on to connect BAT to SYS.  Is BATDRV to Q3 high or low?  Is there a short from BAT to SYS?  Also, if truly BQ24170 with CELLS low, VBATREG =4.2V, battery detect signal should only go to 4.2V not almost to the input voltage.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    TI__Guru**** 166176 points

    Hi Star,

    I haven't heard from you in 7 days.  So, I am going to assume your question is resolved.  If not, please click not resolved or enter a new post.

    Regards,

    Jeff