Other Parts Discussed in Thread: BQ24081
Hi team,
I'm working on a li-ion battery powered device which can run from USB when the battery is discharged. I have selected the TPS2116 to switch between the battery and USB power.
This part of the schematic is shown below:
The system draws ~90mA nominal (150mA max) when running. It can be disabled with a power switch. Not shown is the battery charging circuit (based on BQ24081).
The functionality will be as follows:
- With no USB plugged in, device will run from battery and can be shutdown using the switch.
- With USB plugged in, the device should charge the battery and run the system load from USB. The system can be shutdown using the switch but battery charging will continue until complete.
I have some concerns after reading other question on this forum:
1. Will the TPS2116 work correctly when the USB is unplugged? Are the PR1 resistors enough to pull Vin1 down to 0V? If they are not enough, is the floating input going to cause issue?
2. Will the TPS2116 work correctly when the switch is open? There will be no load at all on the output. Will this cause undesired behaviour? The USB may be plugged in or unplugged in this situation. Does that have any bearing?
I would prefer for VUSB not to show any voltage when running on battery alone (switch open or closed) and would hope that there is no (or minimal) reverse current into the battery in any situation.
Is my design correct? Are the capacitors large enough for the system load?
Thanks,
Chris
