DRQ-12-42-D48 Datasheet, PDF (20/24 Pages) Murata Power Solutions Inc. – 500W Digital Fully Regulated Intermediate DC-DC Bus Converter

DRQ-12/42-D48 Series
500W Digital Fully Regulated
Intermediate DC-DC Bus Converter
TECHNICAL NOTES (CONT.)
Thermal Shutdown
Extended operation at excessive temperature will initiate overtemperature
shutdown triggered by a temperature sensor outside the PWM controller. This
operates similarly to overcurrent and short circuit mode. The inception point
of the overtemperature condition depends on the average power delivered,
the ambient temperature and the extent of forced cooling airflow. Thermal
shutdown uses only the hiccup mode (autorestart) and PMBus configurable
hysteresis.
Start Up Considerations
When power is first applied to the DC-DC converter, there is some risk of start
up difficulties if you do not have both low AC and DC impedance and adequate
regulation of the input source. Make sure that your source supply does not allow
the instantaneous input voltage to go below the minimum voltage at all times.
Use a moderate size capacitor very close to the input terminals. You may
need two or more parallel capacitors. A larger electrolytic or ceramic cap sup-
plies the surge current and a smaller parallel low-ESR ceramic cap gives low
AC impedance.
Remember that the input current is carried both by the wiring and the
ground plane return. Make sure the ground plane uses adequate thickness
copper. Run additional bus wire if necessary.
Input Fusing
Certain applications and/or safety agencies may require fuses at the inputs of
power conversion components. Fuses should also be used when there is the
possibility of sustained input voltage reversal which is not current-limited. For
greatest safety, we recommend a fast blow fuse installed in the ungrounded
input supply line.
Input Under-Voltage Shutdown and Start-Up Threshold
Converters will not begin to regulate properly until the rising input voltage
exceeds and remains at the Start-Up Threshold Voltage (see Specifications).
Once operating, converters will not turn off until the input voltage drops below
the Under-Voltage Shutdown Limit. Subsequent restart will not occur until the
input voltage rises again above the Start-Up Threshold. This built-in hysteresis
prevents any unstable on/off operation at a single input voltage. The over/
under-voltage fault level and fault response and hysterisis can be configured
via the PMBus interface.
Start-Up Time
Start-Up Time (see Specifications) is the time interval between the point when
the rising input voltage crosses the Start-Up Threshold and the output voltage
enters and remains within its specified accuracy band.
These converters include a soft start circuit to control Vout ramp time,
thereby limiting the input inrush current.
The On/Off Remote Control interval from On command to Vout (final ±5%)
assumes that the converter already has its input voltage stabilized above the
Start-Up Threshold before the On command. The interval is measured from the
On command until the output enters and remains within its specified accuracy
band.
including long distributed wiring to a remote power supply. The converter will
operate with no additional external capacitance if these conditions are met.
For best performance, we recommend installing a low-ESR capacitor
immediately adjacent to the converter’s input terminals. The capacitor should
be a ceramic type such as the Murata GRM32 series or a polymer type. More
input bulk capacitance may be added in parallel (either electrolytic or tantalum)
if needed.
Recommended Output Filtering
The converter will achieve its rated output ripple and noise with no additional
external capacitor. However, the user may install more external output capaci-
tance to reduce the ripple even further or for improved dynamic response.
Again, use low-ESR ceramic (Murata GRM32 series) or polymer capacitors.
Mount these close to the converter. Measure the output ripple under your load
conditions.
Use only as much capacitance as required to achieve your ripple and noise
objectives. Excessive capacitance can make step load recovery sluggish or
possibly introduce instability. Do not exceed the maximum rated output capaci-
tance listed in the specifications.
Input Ripple Current and Output Noise
All models in this converter series are tested and specified for input reflected
ripple current and output noise using designated external input/output com-
ponents, circuits and layout as shown in the figures below. The Cbus and Lbus
components simulate a typical DC voltage bus.
TO
OSCILLOSCOPE
CURRENT
PROBE
+Vin
+
LBUS
VIN ^–
+
CBUS
CIN
–
-Vin
CIN = 220μF, ESR < 700mΩ @ 100kHz
CBUS = 220μF, ESR < 100mΩ @ 100kHz
LBUS = 12μH
Figure 3. Measuring Input Ripple Current
+Vout
-Vout
C1 C2
SCOPE
RLOAD
Recommended Input Filtering
The user must assure that the input source has low AC impedance to provide
dynamic stability and that the input supply has little or no inductive content,
C1 = 1μF; C2 = 10μF
LOAD 2-3 INCHES (51-76mm) FROM MODULE
Figure 4. Measuring Output Ripple and Noise (PARD)
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