PRD25 Datasheet, PDF (12/13 Pages) CUI INC – DC-DC CONVERTER

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CUI Inc │ SERIES: PRD25 │ DESCRIPTION: DC-DC CONVERTER
date 05/20/2016 │ page 12 of 13
APPLICATION NOTES
Output Voltage Trimming
The output voltage can be adjusted by using the trim pin and a single fixed resistor (see Figures 4 & 5).Trimming
resistors should have a low temperature coefficient (± 100 ppm/°C or less) and be mounted close to the converter. If the
trim function is not needed, leave the trim pin open.
Figure 4 Trim Adjustments To Decrease
Output Voltage Using A Fixed Resistor
+VIN
+VOUT
Figure 5 Trim Adjustments To Increase
Output Voltage Using A Fixed Resistor
+VIN
+VOUT
ON/OFF
CONTROL
TRIM
RTRIM DOWN
LOAD
ON/OFF
CONTROL
TRIM
RTRIM UP
LOAD
−VIN
−VOUT
−VIN
−VOUT
Note: R_trim-up is the external resistor in Ω
R_trim-down is the external resistor in Ω
V_{O, nom} is the nominal output voltage
V_O is the desired output voltage
Vout
3.3
5
12
A
12775
12775
25000
B
2050
2050
5110
C
5110
5110
10000
Remote On/Off Control
The DC-DC converter can be ordered with either positive or negative logic.See page 2 for enable/disable details for both
positive and negative logic options.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 that there is a finite time in
milliseconds between the 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.
Cautions when using the On/Off control:
1. To retain full output circuit isolation, control the On/Off from the input side only.
2. 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.
3. Do not apply voltages to the On/Off pin when there is no input power voltage, otherwise the converter may be
permanently damaged.
+VCC
Figure 6. Driving The On/Off Control Pin
(Suggested Circuit)
ON/OFF
CONTROL
-VIN
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