BQ2973: Battery is not powering the circuit (

Fernando Fontes

Prodigy 55 points

Part Number: BQ2973

Tool/software:

Hi guys,

I've designed an UVP/OVP circuit to protect the 18650 lithium battery. However, I'm struggling to make it work.

The schematic looks something like this:

After placing the battery nothing happens. However, placing the multimeter between GND and G1 of the DMG6968 the FETs seems to start conducting and everything works. Is this because of the gate threshold? VGSth is 0.9V maximum, so I guess no...

Any suggestion? What could be the issue here?

Thank you for the ongoing support,

Best regards,

Fernando Fontes

5 months ago

+1 Alexis_H 5 months ago

TI__Genius 17835 points

Hello Fernando,

After reviewing your schematic:

We typically recommend adding a 5Mohm resistor to the gate source of each external FET to deplete any charge on the gate-source capacitance.
When the battery is connected for the first time, the DSG circuit might not be enabled. You need to short the V-pin to the VSS pin. Alternatively, you can connect the charger between the Pack + and Pack- terminals in the system. This is mentioned in 'CAUTION' under Section 8.4.1 Normal Operation of the BQ297xx Cost-Effective Voltage and Current Protection Integrated Circuit for Single-Cell Li-Ion and Li-Polymer Batteries datasheet (Rev. I).

Best Regards,
Alexis