HPQ Series
Isolated High Power Quarter Brick DC/DC Converters
ductor capacitors (www.sanyo.com) can be especially effective for further
reduction of ripple/noise.
Technical Notes
Removal of Soldered Converters from Printed Circuit Boards
The most effective combination of external I/O capacitors will be a function
of line voltage and source impedance, as well as particular load and layout
conditions.
Should removal of the converter from its soldered connection be needed,
thoroughly de-solder the pins using solder wicks or de-soldering tools. At no
time should any prying or leverage be used to remove boards that have not
been properly de-soldered first.
Start-Up Threshold and Undervoltage Shutdown
Under normal start-up conditions, these converters will not begin to regulate
properly until the ramping input voltage exceeds the Start-Up Threshold. Once
operating, devices will turn off when the applied voltage drops below the Und-
ervoltage Shutdown point. Devices will remain off as long as the undervoltage
condition continues. Units will automatically re-start when the applied voltage
is brought back above the Start-Up Threshold. The hysteresis built into this
function avoids an indeterminate on/off condition at a single input voltage. See
Performance/Functional Specifications table for actual limits.
Input Source Impedance
These converters must be driven from a low ac-impedance input source. The
DC/DC’s performance and stability can be compromised by the use of highly
inductive source impedances. The input circuit shown in Figure 2 is a practical
solution that can be used to minimize the effects of inductance in the input
traces. For optimum performance, components should be mounted close to the
DC/DC converter.
I/O Filtering, Input Ripple Current, and Output Noise
Start-Up Time
All models in this Series are tested/specified for input ripple current (also called
input reflected ripple current) and output noise using the circuits and layout
shown in Figures 2 and 3. External input capacitors (CIN in Figure 2) serve
primarily as energy-storage elements.
The VIN to VOUT Start-Up Time is the interval between the point at which a ramp-
ing input voltage crosses the Start-Up Threshold voltage and the point at which
the fully loaded output voltage enters and remains within its specified accuracy
band. Actual measured times will vary with input source impedance, external
input capacitance, and the slew rate and final value of the input voltage as it
appears to the converter. The On/Off to VOUT start-up time assumes that the
converter is turned off via the Remote On/Off Control with the nominal input
voltage already applied.
They should be selected for bulk capacitance (at appropriate frequencies), low
ESR, and high rms-ripple-current ratings. The switching nature of
DC/DC converters requires that dc voltage sources have low ac impedance as
highly inductive source impedance can affect system stability. In Figure 2, CBUS
and LBUS simulate a typical dc voltage bus. Your specific system configuration
may necessitate additional considerations.
On/Off Control
The primary-side, Remote On/Off Control function can be specified to operate
with either positive or negative polarity. Positive-polarity devices ("P" suffix)
are enabled when the on/off pin is left open or is pulled high. Positive-polarity
devices are disabled when the on/off pin is pulled low (with respect to –Input).
Negative-polarity devices are off when the on/off pin is high and on when the
on/off pin is pulled low. See Figure 4.
In critical applications, output ripple/noise (also referred to as periodic and ran-
dom deviations or PARD) can be reduced below specified limits using filtering
techniques, the simplest of which is the installation of additional external out-
put capacitors. Output capacitors function as true filter elements and should be
selected for bulk capacitance, low ESR, and appropriate frequency response.
In Figure 3, the two copper strips simulate real-world pcb impedances between
the power supply and its load. Scope measurements should be made using
BNC connectors or the probe ground should be less than ½ inch and soldered
directly to the fixture.
Dynamic control of the remote on/off function is best accomplished with a me-
chanical relay or an open-collector/open-drain drive circuit (optically isolated if
appropriate). The drive circuit should be able to sink appropriate current (see
Performance Specifications) when activated and withstand appropriate voltage
when deactivated.
All external capacitors should have appropriate voltage ratings and be located
as close to the converter as possible. Temperature variations for all relevant
parameters should be taken into consideration. OS-CONTM organic semicon-
7
COPPER STRIP
+SENSE
8
+OUTPUT
TO
CURRENT
PROBE
OSCILLOSCOPE
RLOAD
SCOPE
C1
C2
3
1
+INPUT
–INPUT
4
5
L
BUS
+
–OUTPUT
–SENSE
VIN
C
BUS
CIN
COPPER STRIP
–
C1 = 1μF CERAMIC
C2 = 10μF TANTALUM
See specs for component values.
LOAD 2-3 INCHES (51-76mm) FROM MODULE
Figure 2. Measuring Input Ripple Current
Figure 3. Measuring Output Ripple/Noise (PARD)
www.murata-ps.com
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000
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