BQ25700A: noise, heating and problem with ADC
Part Number: BQ25700A
I am trying to use a BQ2700A as a boost battery charger.
(Note: in the future I may need higher input voltage, e.g. 12V 3A)
Here's what I have so far:
The problem I'm having is that the charger only seems to operate in buck mode.
Do people have any thoughts??
I got the 'scope out, and I found that the PWM control seems to be really unstable. For 12V 250mA -> 6.1V ?? mA, I get the following waveforms on SW1 (yellow) and SW2 (green). I am using very short probe connections to avoid noise pickup. I would expect SW1 to be nice an periodic, and SW2 to usually sit at 6V with occasional dips to ground to recharge bootstrap capacitor 2.
I checked that the switching frequency is correct and the switches aren't nasty/noisy (scope has 100MHz bandwidth), which is good. However, SW1 and SW2 don't have waveforms like I would expect - I would expect SW2 be high almost all the time.
However, the charger won't boost. Reducing the input to 5.1V, the Vsys sags to (i.e. out of regulation). I'm not really sure what's going on here - SW1 and SW2 seem to be operating at different rates. (Ch4 is the low side gate for SW2 node)
So I did some more investigating and made 2 changes:
We are glad that we were able to resolve this issue, and will now proceed to close this thread.
If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.
In reply to Jonathan Bradshaw98:
I am reviewing your question and will get back to you soon. I am reviewing the waveforms and test conditions you have captured.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.