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PKJ4000EPIEN/LZT146025R7AEricssonPowerModules,March2007
Operating Information
Over Temperature Protection (OTP)
The PKJ 4000E Series DC/DC converters are protected from
thermal overload by an internal over temperature shutdown
circuit. When the PCB temperature (centre of PCB ) exceeds
135 °C the converter will shut down immediately (latching).
The converter can be restarted by cycling the input voltage or
using the remote control function.
Input And Output Impedance
The impedance of both the power source and the load will
interact with the impedance of the DC/DC converter. It is
most important to have a ratio between L and C as low as
possible, i.e. a low characteristic impedance, both at the
input and output, as the converters have a low energy storage
capability. The PKJ 4000E Series DC/DC converters have been
designed to be completely stable without the need for external
capacitors on the input or the output circuits. The performance
in some applications can be enhanced by addition of external
capacitance as described under maximum capacitive load. If
the distribution of the input voltage source to the converter
contains significant inductance, the addition of a 100F
capacitor across the input of the converter will help insure
stability. This capacitor is not required when powering the
DC/DC converter from a low impedance source with short, low
inductance, input power leads.
Parallel Operation
The PKJ 4000E Series DC/DC converters can be paralleled for
redundancy if external "O"-ring diodes are used in series with
the outputs. It is not recommended to parallel the PKJ 4000E
Series DC/DC converters for increased power without using
external current sharing circuits.
Maximum Capacitive Load
When powering loads with significant dynamic current
requirements, the voltage regulation at the load can be
improved by addition of decoupling capacitance at the load.
The most affective technique is to locate low ESR ceramic
capacitors as close to the load as possible, using several
capacitors to lower the effective ESR. These ceramic capacitors
will handle short duration high-frequency components of
dynamic load changes. In addition, higher values of electrolytic
capacitors should be used to handle the mid-frequency
components. It is equally important to use good design practise
when configuring the DC distribution system.
Low resistance and low inductance PCB (printed circuit board)
layouts and cabling should be used. Remember that when
using remote sensing, all resistance, inductance and capacitance
of the distribution system is within the feedback loop of the
converter. This can affect on the converters compensation and
the resulting stability and dynamic response performance. As
a “rule of thumb”, 100 F/A of output current can be used
without any additional analysis. For example with a 25A
converter, values of decoupling capacitance up to 2500 F
can be used without regard to stability. With larger values of
capacitance, the load transient recovery time can exceed the
specified value. As much of the capacitance as possible should
be outside the remote sensing loop and close to the load. The
absolute maximum value of output capacitance is 10 000 F.
For values larger than this, please contact your local Ericsson
Power Modules representative.
Current Limit Protection
The PKJ 4000E Series DC/DC converters include current
limiting circuitry that allows them to withstand continuous
overloads or short circuit conditions on the output. The output
voltage will decrease towards zero for output currents in excess
of max output current (Iomax).
The converter will resume normal operation after removal of the
overload. The load distribution system should be designed to
carry the maximum output short circuit current specified.
Over Voltage Protection (OVP)
The PKJ 4000E Series DC/DC converters have latching output
overvoltage protection. In the event of an overvoltage condition,
the converter will shut down immediately. The converter can
be restarted by cycling the input voltage or using the remote
control function.