3.3.17
PFC Vout SS end (delta)
Size:2 bits
Sets the voltage at which the PFC terminates the soft-start and the system begins the LLC soft-start.
Available values are:
•
19.5 mV - 3.8 V
•
29.3 mV - 5.7 V
•
39.1 mV - 7.6 V
•
58.6 mV - 11.4 V
Use
The above values are intended as a negative delta with respect to the “PFC Vout target” parameter.
The PFC soft-start end voltage will be therefore:
Equation 9
"PFC Vout SS end" = "PFC Vout target" − "PFC Vout SS end delta "
(9)
The values on the left are referred to the PFC_FB pin, that corresponds to values on the right if the bulk voltage
divider is designed with the standard ratio k = 5.16 · 10
-3
(i.e. 484.5 V on the bulk voltage correspond to 2.5 V on
the PFC_FB pin).
If other bulk voltage dividers are used, the values on the left can be used to set the output voltage.
3.3.18
PFC UVP threshold (delta)
Bits: 3
Sets the UVP level for PFC output voltage.
Available values are:
•
0.156 V - 30 V
•
0.234 V - 45 V
•
0.313 V - 61 V
•
0.391 V - 76 V
•
0.469 V - 91 V
•
0.547 V - 106 V
•
0.625 V - 121 V
•
0.703 V - 136 V
Use
The above values are intended as a negative delta with respect to the “PFC Vout target” parameter.
In fact, the UVP threshold is defined as
Equation 10
"PFC UVP threshold" = "PFC Vout target" − "PFC UVP threshold delta "
(10)
The values on the left are referred to the PFC_FB pin, that corresponds to values on the right if the bulk voltage
divider is designed with the standard ratio k = 5.16 · 10
-3
(i.e. 484.5 V on the bulk voltage correspond to 2.5 V on
the PFC_FB pin).
If other bulk voltage dividers are used, the values on the left can be used to set the output voltage.
3.3.19
PFC SW OVP threshold (delta)
Size: 2 bits
Sets the PFC SW OVP level.
Available values are:
•
51.3 mV - 10 V
•
78.1 mV - 15 V
•
105 mV - 20 V
•
SW OVP disabled
UM3002
PFC parameters
UM3002
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Rev 1
page 18/42