cui.com

CUI Inc

│ SERIES: VGDS1-SIP │ DESCRIPTION: DC-DC CONVERTER

date

09/07/2012 │ page 4 of 5

1.

Input filtering

To reduce the reflected 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 filtering is required, the capacitance may be increased, or expanded to an LC network as shown in Figure 1.

2.

Output filtering

An output capacitor is needed to meet output ripple requirements as shown in Table 2. Output capacitance may be increased for ad-

ditional filtering, 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 specifications.

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 sufficient head room for the regulator. An additional benefit 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.

APPLICATION NOTES

+Vin

+Vout

COM

DC

C

L

L

DC

L

C

C

-Vout

-Vin

Figure 1

Table 1

Table 2

Figure 2

+Vin

-Vin

+Vin

-Vin

+Vout

-Vout

COM

+Vout

DC DC

DC DC

COM

-Vout

REG

REG

REG

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

24 V

0.33 μF

Input Voltage

External Input

Capacitance

5 V

4.7 μF

12 V

2.2 μF

15 V

2.2 μF

24 V

1.0 μF