2 Wiring to Input/Output
Pin
2.1 Wiring Input Pin
(1) External fuse
¡
Fuse is not built-in on input side. In order to protect the unit, install
the normal-blow type fuse on input side.
¡
When the input voltage from a front end unit is supplied to multiple
units, install the normal-blow type fuse in each unit.
Table 2.1 Recommended fuse (Normal-blow type)
Model
Vin
MH3
5-12 (MHF
O
12)
3.15A
12-24 (MHF
O
24)
2.0A
24-48 (MHF
O
48)
1.6A
(2) External capacitor on the input side
¡
Adding a capacitor Ci near the input pin terminal and reduce re-
flected input noise from a converter.
Please connect the capacitor as needed.
¡
When you use a capacitor Ci, please use the one with high fre-
quency and good temperature characteristics.
¡
If the power supply is to be turned ON/OFF directly with a switch,
inductance from the input line will induce a surge voltage several
times that of the input voltage and it may damage the power sup-
ply. Make sure that the surge is absorbed, for example, by con-
necting an electrolytic capacitor between the input pins.
¡
If an external filter containing L (inductance) is added to the input
line, or a wire from the input source to the DC-DC converter is
long, not only the reflected input noise becomes large, but also
the output of the converter may become unstable. In such case,
connecting Ci to the input pin terminal is recommended.
¡
If you use an aluminum electrolytic capacitor, please pay attention
to its ripple current rating.
Ci
Fuse
-Vin
+Vin
Input
Fig2.1 Connecting Example of an External Capacitor to the Input Side
Table 2.2 Recommended Capacitance of an External Capacitor on the Input Side [ F]
Model
Vin
MH3
5-12 (MHF
O
12)
10-220
12-24 (MHF
O
24)
10-100
24-48 (MHF
O
48)
10-47
*
Please adjust the capacitance in accordance with a degree of the
effect you want to achieve.
(3) Reverse input voltage protection
¡
If a reverse polarity voltage is applied to the input pin terminal, the
power supply will fail. If there is a possibility that a reverse polarity
voltage is applied, connect a protection circuit externally as de-
scribed below.
Fuse
Input
+Vin
-Vin
Schottky Barrier
Diode
Fig2.2 Reverse Input Voltage Protection
2.2 Wiring Output Pin
¡
If you want to further reduce the output ripple noise, connect an
electrolytic capacitor or a ceramic capacitor Co to the output pin
terminal as shown below.
Co
Load
-Vout
+Vout
(a) MHFS
Co
Load
-Vout
+Vout
COM
Co
Load
(b) MHFW
Fig.2.3 Connecting Example of an External Capacitor to the Output Side
Table 2.3 Recommended Capacitance of External Capacitor on the Output Side [ F]
Model
Vout
MH3
3.3
0 - 220
5
0 - 220
9
0 - 100
12
0 - 100
15
0 - 100
±12
0 - 100
±15
0 - 100
*
If you use a ceramic capacitor, keep the capacitance within the
range between about 0.1 to 22uF.
*
Please adjust the capacitance in light of the effect you want to
achieve.
*
If you need to use an external capacitor whose capacitance ex-
ceeds the range provided in Table 2.3, please contact us.
MH3
DC-DC Converters PCB Mount Type
Instruction Manual
MH-10
June 26, 2020
