Datasheet

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CUI Inc │ SERIES: PQA50-D │ DESCRIPTION: DC-DC CONVERTER date 07/14/2015 │ page 6 of 7
1. Requirement on output load
Toensurethismodulecanoperateefcientlyandreliably,theminimumoutputloadcannotbelessthan5%ofthefullloadduring
operation. If the actual output power is small, please connect a resistor at the output end in parallel to increase the load.
2. Recommended circuit
This series has been tested according to the following recommended testing circuit before leaving the factory. This series should be
testedunderload(seeFigure3).Ifyouwanttofurtherdecreasetheinput/outputripple,youcanincreasecapacitanceproperlyor
choose capacitors with low ESR (see table 3). However, the capacitance must not exceed the maximum capacitive load or a start-up
problem might arise (see table 4).
3. Output Voltage Trimming
Leave open if not used.
        FormulaforTrimResistor
Application Circuit for Trim Pin
(part in broken line is the interior of models)
Note: Value for R1, R2, R3, and Vref (see Table 5)
R
T
: Trim Resistor
        a:User-denedparameter,noactualmeanings
Vo': The trim up/down voltage
up:
a=
Vre
f
Vo’-Vref
R 1
R=
a
R
2
R-a 2
-R 3
down:
a=
Vre
f
Vo’-Vref
R 2
R= T
T
aR 1
R-a 1
-R 3
APPLICATION NOTES
Figure 3
Table 3 Table 4
Table 5
Figure 4
Vout
(Vdc)
Cin
(µF)
Cout
(µF)
3.3 100 220
5 100 220
12 100 100
15 100 100
24 100 47
Notes: 1. Minimum load shouldn't be less than 5%, otherwise ripple may increase dramatically. Operation under minimum load will not damage the converter, however, they may
 notmeetallspecicationslisted.
2. Maximum capacitive load is tested at input voltage range and full load.
 3.AllspecicationsaremeasuredatTa=25°C,humidity<75%,nominalinputvoltageandratedoutputloadunlessotherwisespecied.
+Vo
0V
R
2
R
1
R
3
V
re f
R
T
Trim
0V
R
2
R
1
R
3
V ref
R
T
Tr
im
+Vo
Tr im up
Tr im down
DC DC
Vin
GND
+Vout
0V
Cin
Vout
(Vdc)
Max.
Capacitive Load
(μF)
3.3 27000
5 18900
12 3700
15 2000
24 1000
Vout
(Vdc)
R1
(kΩ)
R2
(kΩ)
R3
(kΩ)
Vref
(V)
3.3 4.788 2.87 15 1.24
5 2.87 2.87 12.1 2.5
12 11 2.87 22 2.5
15 15 3 22 2.5
24 20 2.308 15 2.5
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