
BCD.00017 Rev. AA, 18-Oct-2010
Page 13 of 18
www.power-one.com
RFS/RDS Series Data Sheet
20W SMT DC-DC Converters, 1.5 – 5VOutput
RDS Series:
r
Output Power vs Ambient Temperature and Airflow
(typically, Vi = 48 V)
0
20
40
60
80
100
120
0
1020
30
40
506070
8090
100
Ambient Temp. (°C)
Ou
tp
u
tP
o
w
e
r(
%
)
0 LFM
200LFM (1 m/s)
400LFM (2 m/s)
Application and Auxiliary Functions
These
converters
do
not
require
any
external
components for proper operation. However, if the
distribution of the input voltage to the converter
contains significant inductance, a capacitor across the
input terminals may be required to stabilize the input
voltage. A minimum of 1
μF, quality electrolytic or
ceramic capacitor is recommended for this purpose.
For output decoupling it is recommend connecting a
1
μF ceramic capacitor directly across the output pins
of the converter.
Shutdown
The remote control pin functions as a normal soft
shutdown. It is referenced to the –Vi pin. With positive
logic, when the shutdown pin is pulled low, the output
is turned off, and the unit goes into a very low input
power mode. RDS models are also available with a
negative shutdown logic.
An open collector switch is recommended to control
the voltage between the shutdown pin and the -Vi pin
of the converter. The shutdown pin is pulled up
internally, so no external voltage source is required.
The user should avoid connecting a resistor between
the shutdown pin and +Vi pin.
The user must take care to ensure that the pin
reference for the control is connected close to the –Vi
pin. The control signal must not be referenced ahead
of EMI filtering, or remotely from the converter. If the
shutdown pin is not used, it can be left open-circuit.
Negative Logic for RDS (suffix -NM6 or -NM6G)
The output of the converter is enabled or disabled by
means of a logic signal (TTL, CMOS, etc.) applied to
the shutdown pin. No output voltage overshoot will
occur, when the converter is turned on. If the
shutdown function is not required, the pin should be
connected with –Vi to enable the output .
Thermal Considerations
The converter is designed for natural or forced
convection cooling. The output power of the converter
is limited by the maximum case temperature (Tc). To
ensure reliable long term operation of the converters,
and to comply with safety agency requirements,
Power-One limits maximum allowable case tempe-
rature (Tc) to 100 °C (see Mechanical Data).