pca9450 with 3.3V input power

[craig3]

We have a production design using the PCA9450 and 5V input voltage. We are porting this design to a system that will have 3.3V input voltage. I'd like to minimize changes to the design to reduce risk. I'm assuming with Vsys/Vin changed from 5V to 3.3V, Buck4 and LDO5 will not operate to nominal, but all of the remaining Buck and LDO outputs will operate normally. All of our 

1) Is my assumption on operations correct?

2) If I'm not using the BUCK4 output, can I leave the LX4 and BUCK4_FB pins of the PCA9450 floating, and do I need to issue an I2C command to explicitly disable BUCK4?

[JosephAtNXP · Accepted solution]

Hi,

Thank you for your interest in NXP Semiconductor products,

1. BUCK4 and LDO5 theoretically could achieve 3.3V outputs if VSYS, INB45 and INL1 are >= 3.3V.

2. If BUCK4 is not used, LX4 should be left floating while BUCK4FB should be tied to INB45.

Regards