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CUI Inc │ SERIES: VHD1-DIP │ DESCRIPTION: DC-DC CONVERTER date 01/13/2014 │ page 4 of 5
APPLICATION NOTES
DC
C
L
DC
C
in
-Vin
+V
-Vout
Figure 1
Input Voltage
External Input
Capacitance
5 V 4.7 μF
12 V 2.2 μF
24 V 1.0 μF
Table 1
Table 2
Figure 2
Output Voltage
External Input
Capacitance
5 V 4.7 μF
9 V 2.2 μF
12 V 1.0 μF
15 V 0.47 μF
REG
DC DC
DC DC
REG
in
-Vin
-Vout
in
-Vin
+V
1. Input ltering
To reduce the reected ripple current and minimize EMI, especially when the converter input is more than 2” away from the DC
source, it is recommended to connect a low ESR electrolytic capacitor between Vin and Gnd. The values suggested are as shown in
Table 1. If additional ltering is required, the capacitance may be increased, or expanded to an LC network as shown in Figure 1.
2. Output ltering
An output capacitor is needed to meet output ripple requirements as shown in Table 2. Output capacitance may be increased for ad-
ditional ltering, but should not exeed 10μF or expanded to an LC network as in Figure 1.
3. Minimum loading
The converter needs a minimum of 10% loading to maintain output regulation. Operation under no-load conditions will not cause im-
mediate damages but may reduce reliability, and cause performance not to meet specications.
4. Regulation
With a semi-regulated design, the converter’s output voltage varies with load current and will change proportionally to the input volt-
age. If regulated output is needed, an external regulator can be used as shown in Figure 2.
5. Protection
The converter has minimal protection against input over-voltage or output over-load, and may be permanently damaged if exposed to
these conditions. An input clamping device can be used for input voltage limiting. An input fuse or an output fuse can also be used to
protect against over-loading.
6. Dual outputs used as a single output
The +Vout and -Vout can be used to obtain a single output that is the sum of the two outputs. In this case, the COM pin shouldn’t be
used.
7. External Regulator
An external 3-terminal regulator can be connected to the output of the converter to achieve full regulation. Make sure the converter’s
output voltage provides sufcient head room for the regulator. An additional benet is that the built-in protection features in the regu-
lator, such as OCP, OTP, etc, will protect the converter also. In a complimentory supply, a negative output regulator must be used to
achieve the negative regulated output.
Note: All specications measured at 25°C, humidity <75%, nominal input voltage, and full load unless otherwise noted.
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