PINSFUNCTIONAL DESCRIPTION
DRAINPIN:
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.
SOURCEPIN:
Power MOSFET source pin. Primary side circuit
commonground connection.
VDD PIN :
This pin providestwo functions:
- It corresponds to the low voltage supply of the
controlpart of the circuit. If V
DD
goes below 8V,
the start-up current source is activated and the
output power MOSFET is switched off untilthe
V
DD
voltage reaches 11V. During this phase,
the internal current consumption is reduced,
the V
DD
pin is sourcing a current of about 2mA
and the COMP pin is shorted to ground. After
that, the current source is shut down, and the
devicetries to startup by switching again.
- This pin is also connected to the error
amplifier, in order to allow primary as well as
secondary regulation configurations. In caseof
primary regulation, an internal 13V trimmed
reference voltage is used to maintain V
DD
at
13V. For secondary regulation, a voltage
between 8.5V and 12.5V will be put on V
DD
pin
by transformer design, in order to stuck the
output of the transconductanceamplifier to the
high state. The COMP pin behaves as a
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
DD
voltage, which
cannot overpass 13V. The output voltage will
be somewhathigher thanthe nominalone, but
still undercontrol.
COMP PIN :
This pin provides two functions :
- 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 componentsvalue. As
stated above, secondary regulation
configurations are also implemented through
the COMPpin.
- When the COMP voltage is going below 0.5V,
the shut-downof the circuit occurs, with a zero
duty cycle for thepower 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 openload condition.
OSC PIN :
An R
T-CT
network must be connected on that pin
to define the switching frequency. Note that
despite the connection of R
T
to VDD,no
significant frequency change occurs for V
DD
varying from 8V to 15V. It provides also a
synchronisationcapability, when connected to an
external frequencysource.
ORDERING NUMBERS
PENTAW AT T HV PENT AWAT T HV ( 022Y) PowerSO- 10
VI Per 100
VI Per 1 00A
VIP er 100 (022Y)
VIPer100A (022Y)
VIPe r 100SP
VIPer100ASP
VIPer100/SP - VIPer100A/ASP
3/20