VIV0105THJ Datasheet, PDF (12/16 Pages) Vicor Corporation – DC to DC Voltage Transformation

VIV0105THJ
PRELIMINARY DATASHEET
5.0 USING THE CONTROL SIGNALS VC, PC, TM, IM
The VTM Control VC pin is an input pin which powers the
internal VCC circuitry when within the specified voltage range
of 12 V to 17 V. This voltage is required in order for the VTM to
start, and must be applied as long as the input is below 26 V.
In order to ensure a proper start, the slew rate of the applied
voltage must be within the specified range. Depending on the
sequencing of the VC with respect to the input voltage, the
behavior during startup will vary as follows:
• Normal Operation (VC applied prior to V_IN): In this case
the controller is active prior to the input. When the input
voltage is applied, the VTM output voltage will track the
input allowing for a soft start (See Figure 11). If the VC
voltage is removed prior to the input reaching 26 V, the
VTM will shut down.
• Stand Alone Operation (VC applied after V_IN): In this
case the VTM output will begin to rise upon the application
of the VC voltage (See Figure 10). The output rate of rise will
vary depending on the amount of output capacitance in
order to limit the inrush current. In this mode of operation,
the maximum output capacitance is 1,000 µF due to
limitations of the inrush limiting circuitry.
Some additional notes on the using the VC pin:
• In most applications, the VTM will be powered by an
upstream PRM, in which case the PRM will provide a 10 ms
VC pulse during startup. In these applications the VC pins of
the PRM and VTM should be tied together.
• The fault response of the VTM is latching. A positive edge on
VC is required in order to restart the unit.
• The VTM is not designed for continuous operation with VC
applied. The VC voltage must be removed within 20 ms of
application.
• The VTM is capable of reverse operation. If a voltage is
present at the output of the VTM which satisfies the
condition
V_OUT > V_{IN • K}
at the time the VC voltage is applied, then energy will be
transferred from secondary to primary. The input to output
ratio of the VTM will be maintained. The VTM will continue
to operate in reverse once the VC voltage is removed as long
as the input and output voltages are within the specified
range.
The VIV0105THJ has not been qualified for continuous
reverse operation.
The Primary Control (PC) pin can be used to accomplish the
following functions:
• Delayed start: Upon the application of VC, the PC pin will
source a constant 100 µA current to the internal RC
network. Adding an external capacitor will allow further
delay in reaching the 2.5 V threshold for module start
• Auxiliary voltage source: Once enabled in regular
operational conditions (no fault), each VTM PC provides a
regulated 5 V, 2 mA voltage source
• Output Disable: PC pin can be actively pulled down in order
to disable the module. Pull down impedance shall be lower
than 850 Ω.
• Fault detection flag: The PC 5V voltage source is internally
turned off as soon as a fault is detected. For system
monitoring purposes (microcontroller interface) faults are
detected on falling edges of PC signal. It is important to
notice that PC doesn’t have current sink capability (only
150 kΩ pull down is present), therefore in an array PC line
will not be capable of disabling all the modules if a fault is
detected on one of them.
The Temperature Monitor (TM) pin provides a voltage
proportional to the absolute temperature of the converter
control IC.
It can be used to accomplish the following functions:
• Monitor the control IC temperature: The temperature in
degrees Kelvin is equal to the voltage on the TM pin scaled
by x100. (i.e. 3.0 V = 300°K = 27ºC). It is important to
remember that V^•I Chips are multi-chip modules, whose
temperature distribution greatly vary for each part number as
well with input/output conditions, thermal management and
environmental conditions. Therefore, TM cannot be used to
thermally protect the system.
• Fault detection flag: the TM voltage source is internally
turned off as soon as a fault is detected.
The Current Monitor (IM) pin provides a voltage proportional
to the output current of the VTM. The voltage will vary
between 0.3 V and 2.1 V over the output current range of the
VTM (See Figure 7). The accuracy of the IM pin will be within
25% under all line and temperature conditions between 50%
and 100% load. The accuracy of the pin can be improved
using a predictive algorithm based on the input voltage and
internal temperature. Please contact Applications Engineering
for more information.
v i c o r p o w e r. c o m
V•I CHIP INC. (A VICOR COMPANY) 25 FRONTAGE RD. ANDOVER, MA 01810 800-735-6200
Rev. 1.5
9/2009
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