VIPER37HE STMicroelectronics, VIPER37HE Datasheet - Page 26

• Manufacturer Part Number: VIPER37HE
• Description: AC/DC Switching Converters ViperPlus Fixed Freq 800V 30mQ 265 Vac
• Manufacturer: STMicroelectronics
• Type: Off Line Switcherr

Specifications of VIPER37HE

• Product Category: AC/DC Switching Converters
• Rohs: yes
• Input / Supply Voltage (max): 23.5 V
• Input / Supply Voltage (min): 8.5 V
• Switching Frequency: 115 kHz
• Supply Current: 3.5 mA
• Operating Temperature Range: - 40 C to + 150 C
• Mounting Style: Through Hole
• Package / Case: SDIP-10
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 25 C
• Number Of Outputs: 1
• Output Power: 25 W

Operation description
8.10
26/35
Table 11.
1. R
Feedback and overload protection (OLP)
The device is a current mode converter: the feedback pin controls the PWM operation,
controls the burst mode, and actives the overload protection.
the internal current mode structure.
With the feedback pin voltage between
sensed and converted into voltage that is applied to the non-inverting pin of the PWM
comparator.
This voltage is compared with the one on the feedback pin through a voltage divider on a
cycle-by-cycle basis. When these two voltages are equal, the PWM logic orders the switch-
off of the Power MOSFET. The drain current is always limited to the I
In case of overload, the feedback pin increases in reaction to this event and when it goes
higher than
the OCP comparator, see
When the feedback pin voltage reaches the threshold V
starts to charge the feedback capacitor (C
V
value of I
During the first startup phase of the converter, after the soft-start time (t
voltage may force the feedback pin voltage to rise up to the
the converter itself.
To avoid this event, the appropriate feedback network must be selected according to the
output load. Moreover, the feedback network fixes the compensation loop stability.
and
The time from the overload detection (VFB =
(VFB =
Equation 5
where I
V
In
as well as being necessary to activate the overload protection.
FBolp
FBolp
Figure 30
Figure 31
LIM
threshold, the converter is turned off and the startup phase is activated with a reduced
.
must be fixed before R
FB
V
FBolp
DDch
Function / component
is the value, reported in
I
Dlim
V
, the capacitor connected to the FB pin (C
CONT pin configurations
FBlin
) can be set by the C
I
to 0.6 mA, see
Dlim
show the two different feedback networks.
reduction + OVP
, the PWM comparator is disabled and the drain current is limited to I
reduction
OVP
OVP
Figure 2
.
T
Table 7
Doc ID 022218 Rev 1
OLP delay
FB
–
.
Table 8
.
value (see
V
=
FBbm
See
See
, when the FB voltage is between V
FB
C
FB
) and when the feedback voltage reaches the
R
≥ 80 k Ω
V
and
Figure 16
Figure 16
LIM
FBlin
×
Figure 30
V
--------------------------------------- -
(1)
V
FBolp
) to the device shutdown
FBlin
FB
I
FB
, (see
FBlin
–
) is part of the compensation circuit
V
and
FBlin
V
, an internal current generator
FBolp
Figure 30
See
See
Table 8
Figure 31
threshold that switches off
Equation 4
Equation 4
R
No
OVP
Dlim
) the drain current is
and
SS
), using the formula:
value.
), the output
Figure 31
FBlin
Figure 30
and
VIPER37
D
Yes
Yes
No
Dlim
AUX
show
by