Part Number:BQ21040
I am working on a prototype hand-held measuring system that incorporates the BQ21040, a mechanical power switch, and a single lithium ion battery. The unit also includes a micro USB port for charging. The hand-held device uses Bluetooth to connect to a tablet or cell phone.
The hand-held device needs to be able to work either when the unit is plugged in (and charging) OR when the device is running on the battery.
I have the prototype board working in both scenarios. But, the charge LED comes on when the battery slide switch is in the off position. I was hoping to always leave the battery connected to the BQ21040 and then a power switch to isolate the rest of the hand-held device. In this way, the battery would charge whenever the cable was plugged in and the charge LED would illuminate... even if the power switch was in the off position. But, this is not working as desired. When I read the documentation my impression is that the B!21040 would go into a high-impedance power saving mode whenever the input voltage was removed.
I know I can move the mechanical power switch in a way to completely isolate the battery. But I was hoping to be able to charge the battery WITHOUT the switch being turned on.
What am I doing wrong here?