Hi
Two units are tested on the same backplane, one is powered on and the other is not powered on. When powered on, the voltage of this product can be backfilled to the chip vdd of the unpowered product through the equalizing line pin, resulting in the output light of the unpowered product, and uneven current phenomenon occurs after multiple tests and tests
Thank you
Hello Yingjiao,
Thank you for your question involving parallel operation of the UCC29002 controller.
When one of the power-supply units is unpowered, its corresponding load-share controller must be disabled to prevent the issue that you are experinceing.
This can be accomplished as described in Section 7.3.6 (page 9) with an example circuit seen in Figure 6 (page 11) in the UCC29002 data sheet:
The Enable/Disable control signal ("SB2" in the figure) comes from the power supply unit and it is low when the PSU is powered on and is high when the PSU is powered off.
This will prevent the load-share controller of the un-powered PSU from attempting to modify the feedback signal.
Regards,
Ulrich
