UCH_SERIES Datasheet, PDF (14/18 Pages) Murata Manufacturing Co., Ltd. – 1.8−15V Output DC/DC Converters

Remote On/Off Control
On the input side, a remote On/Off Control can be ordered with either polarity.
Positive: Standard models 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 +15V. Some models will also turn on at
lower intermediate voltages (see Specifications). Positive-polarity devices are
disabled when the On/Off is grounded or brought to within a low voltage (see
Specifications) with respect to –Vin.
Negative: Optional negative-polarity devices are on (enabled) when the On/
Off is grounded or brought to within a low voltage (see Specifications) with
respect to –Vin. The device is off (disabled) when the On/Off is left open or is
pulled high to approximately +15V with respect to –Vin.
Dynamic control of the On/Off function should be able to sink appropriate
signal current when brought low and withstand appropriate voltage when
brought high. Be aware too that there is a finite time in milliseconds (see
Specifications) 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.
Single Output UCH Models
Isolated, “Half-Brick”
1.8−15V Output DC/DC Converters
There are several CAUTIONs for the On/Off Control:
CAUTION: While it is possible to control the On/Off with external logic if
you carefully observe the voltage levels, the preferred circuit is either an open
drain/open collector transistor, a switch or a relay (which can thereupon be
controlled by logic) returned to negative Vin.
CAUTION: Do not apply voltages to the On/Off pin when there is no input
power voltage. Otherwise the converter may be permanently damaged.
Output Capacitive Load
These converters do not require external capacitance added to achieve rated
specifications. Users should only consider adding capacitance to reduce switch-
ing noise and/or to handle spike current step loads. Install only enough ca-
pacitance 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 specification 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 high-
er capacitance. Also, capacitors with higher ESR may use a larger capacitance.
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MDC_UCH Models.A15 Page 14 of 18