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BQ24650 BQ24650EVM

I am using the EVM circuit design with an added NTC thermistor for temp compensation on the solar panel. I am charging an LiFePO 12.8V battery pack with 18Vmppt from the solar panel. The EVM is working correctly, but my design is not charging.

Issues I have identified already:

SRN-SRP=-1.8V (this should be -0.5V to 0.5V, I have changed R6 to correct this difference but does not fix the issue)

Vbtst-Vph= 0.4V (below 4.2V should drive Q1:B on to recharge the btst capacitor) Could my cap not be increasing my voltage enough?

  • Brett,

    Could you elaborate on what you mean by "not charging"? Is the converter switching (please provide a waveform of the PH node, HIDRV, and LODRV)? Also, what is the voltage on REGN (it should be 6V)?

    Also, I noticed in your  schematic that you do not differentiate between analog ground and power ground. Not following the layout guidelines in the datasheet could impact your performance since the small signals could have noise coupled from the SMPS if proper separate grounding is not used (see Figure 1 in datasheet for an example of what grounds to use on which pins).