Application Note
17 of 63
V 1.2
2018-12-12
5 Output PMIC Controller/ IRPS5401
User guide with DB295 and DB296 demo boards
Set the fixed_ovp_thresh greater than the largest VOUT_COMMAND value that will be seen in the application.
The logic will switch from relative threshold to the fixed threshold when the Enable goes low, (or OPERATION
off command). If Enable goes low with VOUT > fixed_ovp_thresh, an OVP condition will be declared and VOUT
will be clamped low with the LS FET and the TOFF_RAMP down time will not be seen. The SM_ALERT# and the
STATUS bit will not assert because they are masked by the Enable pin = low.
Figure 23
PINK=SM_ALERT#, GREEN=VOUT, After Enable is de-asserted, VOUT drops from 1.5 V to 0.27 V
in 15
µs TOFF_FALL is 1 ms, Fixed_OVP_Thresh=1.35 V, VOUT=1.5 V
4.7
Over Voltage Settings under Steady State
After VOUT has ramped up past 1V (or after VOUT has reached its final value if it is less than 1 V), the OVP
switches to a value that is relative to the voltage set by VOUT_COMMAND. There are eight (8) relative threshold
values from 50mV to 400 mV (above VOUT) in 50 mV increments. The user sets the relative threshold by sending
a VOUT_OV_FAULT_LIMIT value that is greater than the VOUT_COMMAND by the required threshold. If the
VOUT_COMMAND is 1 V, a VOUT_OV_FAULT_LIMIT of 1.4 V (or greater) will cause the relative OVP threshold to
be 400 mV. If the VOUT_COMMAND is reduced to 0.9 V, the relative threshold of 400 mV will cause an OV fault at
1.3 V. If the VOUT_COMMAND increases VOUT to 1.2 V, the relative OVP threshold will be reduced to 200 mV
(FAULT_LIMIT-COMMAND). If the VOUT_COMMAND increases VOUT to 1.4 V, the new relative threshold will be
50 mV. The user can’t cause an OVP fault by setting the VOUT_COMMAND to a value greater than or equal to
the VOUT_OV_FAULT_LIMIT.
The relative OVP threshold will always be 50 mV above the VOUT_COMMAND value in the scenario described
above with the VOUT_COMMAND being increased to the VOUT_OV_FAULT_LIMIT or above.
The user should set the VOUT_OV_FAULT_LIMIT value such that it is > 400 mV above the largest
VOUT_COMMAND value that will be used in the application.
Each loop reports out the relative OVP threshold in Read Only (RO) register xx56h [2:0]. 0 = 50 mV, 1 = 100
mV…up to 7=400 mV. If 2:1 scaling is used, the relative OVP threshold is 2x the value shown.
