2.4 Y Capacitors and noise filters: CY, CX, L1
■
The TUNS300/500/700 series has no internal noise filter.
Connect external noise filters and capacitors (CY) to reduce conduction noise and stabilize
the operation of the power supply.
■
Noise filters should be properly designed when the unit must conform to the EMI/EMS
standards or when surge voltage may be applied to the unit.
■
Install the primary Y capacitor (CY1) as close as possible to the input pins (within 50 mm
from the pins).
A capacitance of 470 pF or more is required.
■
When the total capacitance of CYs exceeds 8,800 pF, input-output withstanding voltage
may be dropped. In this case, either reduce the capacitance of Y capacitors or install a
grounding capacitor between output and FG.
■
Use capacitors with a rated voltage of AC250V which comply with the safety standards
as CY.
2.5 Output capacitors: Co, C40
■
Install an external capacitor, Co, bVOUT and -VOUT pins for stable operation
of the power supply. Recommended capacitance of Co is shown in Table 2.3.
■
Use low impedance electrolytic capacitors with excellent temperature characteristics.
■
When Using at ambient temperatures below 0 ºC, the output ripple voltage increases due
to the characteristics of equivalent series resistor (ESR). In this case, connect three
capacitors, Co, of recommended capacitance in parallel connection.
■
Specifications, output ripple and ripple noise as evaluation data values are measured
according to Fig.2.3.
Table 2.3
Recommended
capacitance
Co
Fig.2.3
Measuring
environment
48V
470uF
470uF
470uF
A-4
12V
2,200uF
2,200uF
2,200uF
28V
1,000uF
1,000uF
1,000uF
Output Voltage
TUNS300F
TUNS500F
TUNS700F
R=50Ω
C=0.01uF
Load
1.5m 50Ω
Coaxial Cable
C40:
12V 10µF
28V 4.7µF
48V 2.2µF
+VOUT
-VOUT
-S
+S
0
0
0
0
Co
+
C40
50mm
Oscilloscope
BW:100MHz
R
C
Applications Manual
TUNS300/500/700
