BQ24650: schematic and pcb review

Hi Yangbo,

Is the input source high impedance, like a solar panel? If not, then I suggest changing to the BQ24610. The BQ24610 regulates input current instead of input voltage, which is recommend when using low impedance power sources.

On the schematic,
1. If the TS pin is not connected to the battery (i.e. you are not using the TS function), then the TS pin resistors need to be sized to place V(TS) =0.6 x VREF.
2. Resistor R56 should be 100k for set battery regulation voltage to 4.2V for single cell charging.
3. MPPSET resistors are currently setting the maximum power point input voltage to 17.5V, which means the charger will not charge unless the input voltage >17.5v.
4. The 10 uF buck converter input capacitor at the drain of U14 is missing. Placement of this capacitor is critical and will require you to relay out your board.

Regarding the layout,
1. When adding the 10uF capacitor, I suggest also adding a 0.1uF noise decoupling capacitor. Placement should provide a tight loop for current to flow from drain of U14 to source of U9=GND=U8 pin 11.
2. Ground of C14 and C15 needs more vias (and/or closer placement) for less resistance to U9 source and U8 pin11 GND.

There is a design spreadsheet at www.ti.com/.../sluc175 to help with schematic component selection.

Regards,
Jeff

Hi Jeff,

Thank you for your comments. The input source is solar panel.

Regards,

Yangbo