PQA50-T Datasheet, PDF (6/7 Pages) CUI INC – DC-DC CONVERTER

For more information, please visit the product page.
CUI Inc │ SERIES: PQA50-T │ DESCRIPTION: DC-DC CONVERTER
date 07/15/2015 │ page 6 of 7
APPLICATION NOTES
1. Requirement on output load
To ensure this module can operate efficiently 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).
Figure 3
Vin
Cin
GND
DC DC
+Vout
0V
Table 3
Table 4
Vout
(Vdc)
3.3
5
12
15
24
Cin
(µF)
100
100
100
100
100
Cout
(µF)
220
220
100
100
47
Vout
(Vdc)
3.3
5
12
15
24
Max.
Capacitive Load
(μF)
27000
18900
3700
2000
1000
                                                                                                          
3. Output Voltage Trimming
Leave open if not used.
_{Fig ure 4 Formu la for Tri m Resist or}
Application Circuit for Trim Pin
(part in broken line is the interior of models)

+Vo
+ Vo
up: RT =
aR2
R 2- a
- R3
a=
Vref
Vo’-Vref
R1
R1
^{VRre2f R 3} _RT ^{Trim VRRr e12f R3 RT Trim}

0V
0V
Tr im up
Tr im down
down: RT=
aR1
R 1- a
- R3
a= ^{Vo’-Vref}
Vref
R2
Note: Value for R1, R2, R3, and Vref (see Table 5)
R_T: Trim Resistor
a: User-defined parameter, no actual meanings
Vo': The trim up/down voltage
Vout
(Vdc)
R1
(kΩ)
R2
R3 Vref
(kΩ) (kΩ) (V)
Table 5
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
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 specifications listed.
2. Maximum capacitive load is tested at input voltage range and full load.
3. All specifications are measured at Ta=25°C, humidity<75%, nominal input voltage and rated output load unless otherwise specified.
cui.com