BCM352x125y300A00
Using the Control Signals PC, TM
Primary Control (PC) pin can be used to accomplish the
following functions:
n Delayed start: At start up, PC pin will source a constant
100µA current to the internal RC network. Adding an external
capacitor will allow further delay in reaching the 2.5V threshold
for module start.
n Synchronized start up: In an array of parallel modules, PC
pins should be connected to synchronize start up across
units. While every controller has a calibrated 2.5V reference
on PC comparator, many factors might cause different timing in
turning on the 100µA current source on each module, i.e.:
– 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.
n Auxiliary voltage source: Once enabled in regular
operational conditions (no fault), each BCM module
PC provides a regulated 5V, 2mA voltage source.
n Output disable: PC pin can be actively pulled down in order
to disable the module. Pull down impedance shall be lower
than 400Ω and toggle rate lower than 1Hz.
n Fault detection flag: The PC 5V 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.
n Note that PC doesn’t have current sink capability (only 150kΩ
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.
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:
n Monitor the control IC temperature: The temperature in
Kelvin is equal to the voltage on the TM pin scaled
by 100. (i.e. 3.0V = 300K = 27ºC). It is important to remember
that VI Chip® products 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.
n 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.
BCM® Bus Converter
Page 13 of 21
Rev 2.0
08/2016
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