unr-1.5 C&D Technologies., unr-1.5 Datasheet - Page 4

• Manufacturer Part Number: unr-1.5
• Description: 8 And 10 Amp Dc/dc Converters
• Manufacturer: C&D Technologies.

www.murata-ps.com
External input capacitors serve primarily as energy-storage elements. They
should be selected for bulk capacitance (at appropriate frequencies), low
ESR, and high rms-ripple-current ratings. The switching nature of modern
DC/DC converters requires that dc input voltage sources have low ac imped-
ance, and highly inductive source impedances can affect system stability.
Your specific system configuration may necessitate additional considerations.
Output ripple/noise (also referred to as periodic and random deviations or
PARD) can be reduced below specified limits using filtering techniques, the
simplest of which is the installation of additional external output capacitors.
Output capacitors function as true filter elements and should be selected for
bulk capacitance, low ESR, and appropriate frequency response. Any scope
measurements of PARD should be made directly at the DC/DC output pins
with scope probe ground less than 0.5" in length.
All external capacitors should have appropriate voltage ratings and be
located as close to the converters as possible. Temperature variations for all
relevant parameters should be taken into consideration.
The most effective combination of external I/O capacitors will be a function
of your line voltage and source impedance, as well as your particular load
and layout conditions. Our Applications Engineers can recommend potential
solutions and discuss the possibility of our modifying a given device’s internal
filtering to meet your specific requirements. Contact our Applications Engi-
neering Group for additional details.
Input Fusing
UNR 15-25W D3 Series DC/DC converters are not internally fused. Certain
applications and or safety agencies may require the installation of fuses at
the inputs of power conversion components. For Murata Power Solutions
UNR D3 Series DC/DC converters, you should use either slow-blow or
normal-blow fuses with values no greater than the following.
Input Overvoltage and Reverse-Polarity Protection
UNR D3 Series DC/DC converters do not incorporate either input overvoltage
or input reverse-polarity protection. Input voltages in excess of the listed
absolute maximum ratings and input polarity reversals of longer than "instan-
taneous" duration can cause permanent damage to these devices.
On/Off Control
The On/Off Control pin may be used for remote on/off operation. UNR D3
Series DC/DC converters are designed so that they are enabled when the
control pin is pulled high or left open (normal mode) and disabled when the
control pin is pulled low (to less than +0.8V relative to Logic Ground). As
shown in Figure 2, both 2.5V
up resistors to V
Dynamic control of the on/off function is best accomplished with a mechani-
cal relay or open-collector/open-drain drive circuit. The drive circuit should
be able to sink appropriate current when activated and withstand appropriate
voltage when deactivated.
Output Voltage
1.5V Models
1.8V Models
2.5V Models
IN
(+Input).
OUT
Fuse Value
and 1.8V
11 Amps
12 Amps
18 Amps
OUT
models have internal 1kΩ pull-
Applying an external voltage to the On/Off Control pin when no input power
is applied to the converter can cause permanent damage to the converter.
The on/off control function, however, is designed such that the converter
can be disabled (control pin pulled low) while input power (system 3.3V
power) is ramping up and then "released" once the input has stabilized.
The time duration between the point at which the converter is released and
its fully loaded output settles to within specified accuracy can be found in
the Performance/Functional Specifications Table. See Start-Up Time for more
details.
Start-Up Time
The V
ramping input voltage crosses the lower limit of the specified input voltage
range (3.0 Volts) and the fully loaded output voltage enters and remains within
it 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 V
the Remote On/Off Control with the nominal input voltage already applied to
the converter. The specification defines the interval between the time at which
the converter is turned on and the fully loaded output voltage enters and
remains within its specified accuracy band. See Typical Performance Curves
for details
Output Overvoltage Protection
UNR D3 Series DC/DC converters do not incorporate output overvoltage
protection. In the extremely rare situation in which the device’s feedback loop
is broken, the output voltage may run to excessively high levels (V
If it is absolutely imperative that you protect your load against any and all
possible overvoltage situations, voltage limiting circuitry must be provided
external to the power converter.
Output Overcurrent Detection
Overloading the output of a power converter for an extended period of
time will invariably cause internal component temperatures to exceed their
maximum ratings and eventually lead to component failure. High-current-
carrying components such as inductors, FET's and diodes are at the highest
risk. UNR D3 Series DC/DC converters incorporate an output overcurrent
detection and shutdown function that serves to protect both the power
converter and its load.
IN
to V
Single Output, Non-Isolated, 3.3V
OUT
Start-Up Time is the interval between the time at which a
OUT
Start-Up Time assumes the converter is turned off via
Technical enquiries email: [e-mail], tel:
Figure 2. Driving the On/Off Control Pin
+INPUT
ON/OFF
CONTROL
LOGIC
GROUND
8 and 10 Amp DC/DC Converters
UNR D3 SERIES
1kΩ
MDC_UNR15-25W Page 4 of 8
IN
to 1.5/1.8/2.5V
[phone]
OUT
= V
IN
).
OUT