VIB0002TFJ
PRELIMINARY DATASHEET
5.0 USING THE CONTROL SIGNALS TM AND PC
6.0 FUSE SELECTION
The PC control pin can be used to accomplish the following
functions:
V•I Chips are not internally fused in order to provide flexibility
in configuring power systems. Input line fusing of V•I Chips is
recommended at system level, in order to provide thermal
protection in case of catastrophic failure.
• Delayed start: At start-up, PC pin will source a constant
100 uA current to the internal RC network. Adding an
external capacitor will allow further delay in reaching the
2.5 V threshold for module start.
The fuse shall be selected by closely matching system
requirements with the following characteristics:
• Synchronized start up: In a parallel module array, PC pins
shall be connected in order to ensure synchronous start of all
the units. While every controller has a calibrated 2.5 V
reference on PC comparator, many factors might cause
different timing in turning on the 100 uA current source on
each module, i.e.:
• Current rating (usually greater than maximum BCM current)
• Maximum voltage rating (usually greater than the maximum
possible input voltage)
• Ambient temperature
• Nominal melting I2t
• Recommended fuse: ≤2.5 A Bussmann PC-Tron or
SOC type 36CFA.
– Different VIN slew rate
– Statistical component value distribution
By connecting all PC pins, the charging transient will be
shared and all the modules will be enabled synchronously.
• Auxiliary voltage source: Once enabled in regular
operational conditions (no fault), each BCM PC provides a
regulated 5 V, 2 mA voltage source.
• Output Disable: PC pin can be actively pulled down in order
to disable module operations. Pull down impedance shall be
lower than 400 Ω and toggle rate lower than 1 Hz.
• Fault detection flag: The PC 5 V voltage source is internally
turned off as soon as a fault is detected. After a minimum
disable time, the module tries to re-start, and PC voltage is
re-enabled. 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 typical pull down is present),
therefore, in an array, PC line will not be capable of disabling
all the modules if a fault occurs on one of them.
The temperature monitor (TM) pin provides a voltage propor-
tional 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
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. After a minimum
disable time, the module tries to re-start, and TM voltage is
re-enabled.
Rev. 1.3
9/2009
Page 12 of 16
V•I CHIP INC. (A VICOR COMPANY) 25 FRONTAGE RD. ANDOVER, MA 01810 800-735-6200
vicorpower.com
VICOR [ VICOR CORPORATION ]
