viper50b STMicroelectronics, viper50b Datasheet - Page 3

• Manufacturer Part Number: viper50b
• Description: Smps Primary I.c.
• Manufacturer: STMicroelectronics

ORDERING NUMBERS
PINS FUNCTIONAL DESCRIPTION
DRAIN PIN:
Integrated power MOSFET drain pin. It provides
internal bias current during start-up via an
integrated high voltage current source which is
switched off during normal operation. The device
is able to handle an unclamped current during its
normal operation, assuring self protection against
voltage surges, PCB stray inductance, and
allowing a snubberless operation for low output
power.
SOURCE PIN:
Power MOSFET source pin. Primary side circuit
common ground connection.
VDD PIN :
This pin provides two functions :
-
-
It corresponds to the low voltage supply of the
control part of the circuit. If V
the start-up current source is activated and the
output power MOSFET is switched off until the
V
the internal current consumption is reduced,
the V
and the COMP pin is shorted to ground. After
that, the current source is shut down, and the
device tries to start up by switching again.
This pin is also connected to the error
amplifier, in order to allow primary as well as
secondary regulation configurations. In case of
primary regulation, an internal 13V trimmed
reference voltage is used to maintain V
13V. For secondary regulation, a voltage
between 8.5V and 12.5V will be put on V
by transformer design, in order to stuck the
output of the transconductance amplifier to the
high state. The COMP pin behaves as a
DD
voltage reaches 11V. During this phase,
DD
PENT AW ATT HV
pin is sourcing a current of about 2mA
VIPer50B
DD
goes below 8V,
PENTAW AT T HV (022Y)
DD
VIPer50B (022Y)
DD
pin
at
COMP PIN :
This pin provides two functions :
-
-
OSC PIN :
An R
to define the switching frequency. Note that
despite the connection of R
significant frequency change occurs for V
varying from 8V to 15V. It provides also a
synchronisation capability, when connected to an
external frequency source.
constant current source, and can easily be
connected to the output of an optocoupler.
Note that any overvoltage due to regulation
loop failure is still detected by the error
amplifier through the V
cannot overpass 13V. The output voltage will
be somewhat higher than the nominal one, but
still under control.
It is the output of the error transconductance
amplifier, and allows for the connection of a
compensation network to provide the desired
transfer function of the regulation loop. Its
bandwidth can be easily adjusted to the
needed value with usual components value. As
stated
configurations are also implemented through
the COMP pin.
When the COMP voltage is going below 0.5V,
the shut-down of the circuit occurs, with a zero
duty cycle for the power MOSFET. This feature
can be used to switch off the converter, and is
automatically activated by the regulation loop
(whatever is the configuration) to provide a
burst mode operation in case of negligible
output power or open load condition.
T
-C
T
network must be connected on that pin
above,
secondary
Pow erSO-10
VIPer50BSP
DD
VIPER50B/BSP
T
voltage, which
to V
regulation
DD
, no
3/20
DD