VIPER28 STMicroelectronics, VIPER28 Datasheet - Page 22

• Manufacturer Part Number: VIPER28
• Description: VIPerPlus family: fixed frequency high performance off line high voltage converter
• Manufacturer: STMicroelectronics

Operation descriptions
22/32
Equation 7
Equation 8
The R
The C
The
considered instead of C
satisfy, in all case, the loop stability and the enough OLP delay time alike.
Figure 24. FB pin configuration (option 1)
Figure 25. FB pin configuration (option 2)
Equation 5
FB(DYN)
FB1
capacitor fixes the OLP delay and usually C
is the dynamic resistance seen by the FB pin.
can be still used to calculate the OLP delay time but C
Rfb1
Cfb1
FB
. Using the alternative compensation network, the designer can
Cfb
f
f
PFB
PFB
Cfb
Doc ID 15028 Rev 4
1
=
=
2
2
⋅
⋅
⋅ π
⋅ π
CONTROL
PWM
R
C
C
FB
FB
FB
CONTROL
REFERENCES
BURST-MODE
PWM
1
(
DYN
⋅
⋅
REFERENCES
(
(
BURST-MODE
R
R
1
FB
)
FB
+
1
(
DYN
4.8V
R
+
FB
R
FB1
4.8V
)
FB
OLP comparator
1
⋅
R
(
DYN
BURST-MODE
results much higher than C
PWM
From sense FET
+
+
OLP comparator
-
-
FB
LOGIC
1
)
BURST-MODE
)
)
PWM
From sense FET
+
+
-
-
LOGIC
To disable logic
To PWM Logic
To disable logic
BURST
FB1
To PWM Logic
BURST
has to be
VIPER28
FB
.