Datasheet

RUW15 Series
Isolated Ultra-Wide Input DC/DC Converters
KDC_RUW15.B02 Page 3 of 13
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SAFETY
UL 60950
The RUW15 series has been recognised by Underwriters Laboratory (UL) to UL 60950 for reinforced insulation to a working voltage of 250Vrms in maximum temperature as shown
in the derating graphs.
The RUW15 series of converters are not internally fused so to meet the requirements of UL a 3A anti-surge input line fuse should always be used. File number E151252 applies.
RoHS COMPLIANCE INFORMATION
This series is compatible with RoHS soldering systems with a peak wave solder temperature of 260ºC for 10 seconds. The pin termination finish
on this product series is a Gold flash (0.05-0.10 micron) over Nickel Preplate. The series is backward compatible with Sn/Pb soldering systems.
Tinned tabs are provided along the case edges to provide mechanical support through slots in the PCB. Hand soldering of these tabs may be
necessary to ensure satisfactory joint quality.
For further information, please visit www.murata-ps.com/rohs
APPLICATION NOTES
The RUW15 can be used as a general purpose wide input DC/DC converter simply with the addition of the recommended input capacitor, low ESR type 10uF.
Output Capacitors
The RUW series does not require output capacitors to meet datasheet specification. To meet datasheet specifications, total output capacitance should not exceed:
Output Voltage (V) Max. Recommended Output Capacitance (µF)
5 1000
12 470
24 220
Remote ON/OFF control
The remote ON/OFF input to the RUW15 converter is referenced to the primary ground and when pulled below 0.5V, the RUW15 will not operate. The RUW15 will be
operational if the pin is left open. In noisy environments, it is recommended to decouple the remote ON/OFF pin to ground with a 10nF capacitor.
Hold-up
If hold-up of the output is required on input drop-outs such as occur on battery changeovers, the RUW15 has an optional hold-up feature (-H versions) which maintains
the output if the input voltage falls to zero. The hold-up time can be set by the connection of an external capacitor across the –Vint and +Vint pins. The hold-up time is
independent of the input voltage applied before drop-out
Configuration for extended hold-up time
This capacitor is charged by the RUW15 to around 80 V and is internally switched into the RUW15 input upon input voltage failure. An internal diode prevents this high
voltage appearing on the RUW15 input pins. The capacitor is referenced to the input ground of the RUW15 and therefore should have appropriate isolation clearance to the
RUW15 output circuitry.
As drop-outs are not expected to occur in quick succession, the capacitor is allowed to recharge slowly over about one minute before full hold-up is again available. This
helps to minimise internal stresses in the RUW15 converter. As an example, EN50155 requirement to maintain output for 30 ms on supply change-over (Class C2) is met
with a capacitor of 220 uF rated at 100 V for any nominal input voltage up to 110 VDC with the RUW15 operating at maximum load.
The benefit conferred by the hold-up option is most evident when hold-up from low nominal voltages is required even if the wide input range of the RUW15 is not needed.
In the above example to achieve 30 ms holdup with a capacitor across the input in a 24V nominal system, an expensive and large capacitor of 3900uF would be required
rated at higher than the maximum input voltage.
The below graph shows values of capacitance against hold-up time for 15W loading. At lighter loads the hold-up time increases proportionally. In some applications the
external capacitor could be made up from parallel multilayer ceramic parts which would dramatically improve lifetime compared with alternative electrolytic types.
ms
0
10
20
30
40
50
60
70
0 50 100 150 200 250 300
5v
12v
24v
µF