P9025AC FOD TUNING GUIDE
6
REVISION 08/26/15
AN-886
Figure 3. P9025AC FOD2 Global Offset Shift vs. FOD2 Resistance to GND
Option #1: Disabling FOD
Disabling FOD can be done with a few simple steps:
First, P9038 Tx needs to be configured with GPIO4 connected to LDO2p5V with a resistor so that the pin is always at 2.5V during
startup. This will disable the P9038 from shutting down due to changes from expected input power levels that deviate from the
reported power value from the Rx.
Second, the FOD1 pin on the P9025AC Rx should be connected to GND. This will have the effect of selecting the
pre-programmed Bank 10, which maxes out the reported power level. If using the P9025AC-R-EVK reference board, this can be
accomplished by placing a zero-ohm resistor in R4.
Third, the resistor from FOD2 to GND on the P9025AC Rx should be set to 20k
. This will add +300 mW of offset to the reported
power value and make it so that FOD-invoked shutdowns cannot happen when using the P9038, and will be very unlikely when
using the P9025AC with other WPC transmitters. If using the P9025AC-R-EVK reference board, this is resistor R5.
