Datasheet

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UEE 150W Series
Isolated, High-Density, Eighth-Brick
DOSA Low Profi le DC-DC Converters
MDC_UEE 150W_Series.A02 Page 34 of 35
Remote On/Off Control
On the input side, a remote On/Off Control can be specifi ed with either positive
or negative logic logic.
Positive: Models equipped with positive logic are enabled when the On/Off
pin is left open or is pulled high to +Vin with respect to –Vin. An internal bias
current causes the open pin to rise to approximately +13.5V. Some models will
also turn on at lower intermediate voltages (see Specifi cations). Positive-logic
devices are disabled when the On/Off is grounded or brought to within a low
voltage (see Specifi cations) with respect to –Vin.
Negative: Models with negative logic are on (enabled) when the On/Off is
grounded or brought to within a low voltage (see Specifi cations) with respect to
–Vin. The device is off (disabled) when the On/Off is left open or is pulled high
to approximately +13.5V with respect to –Vin.
Dynamic control of the On/Off function should be able to sink the speci-
fi ed signal current when brought low and withstand appropriate voltage
when brought high. Be aware too that there is a fi nite time in milliseconds
(see Specifi cations) between the time of On/Off Control activation and stable,
regulated output. This time will vary slightly with output load type and current
and input conditions.
Output Capacitive Load
These converters do not require external capacitance added to achieve rated
specifi cations. Users should only consider adding capacitance to reduce switch-
ing noise and/or to handle spike current step loads. Install only enough capaci-
tance to achieve noise objectives. Excess external capacitance may cause
regulation problems, slower transient response and possible instability. Proper
wiring of the Sense inputs will improve these factors under capacitive load.
The maximum rated output capacitance and ESR specifi cation is given for a
capacitor installed immediately adjacent to the converter. Any extended output
wiring or smaller wire gauge or less ground plane may tolerate somewhat higher
capacitance. Also, capacitors with higher ESR may use a larger capacitance.
Figure 10. Trim Connections To Decrease Output Voltages
LOAD
R
TRIM DOWN
+VOUT
+VIN
–VIN
ON/OFF
CONTROL
TRIM
+SENSE
–VOUT
–SENSE
Figure 11. Driving the On/Off Control Pin (suggested circuit)
ON/OFF
CONTROL
-VIN
+VCC