rev.
page 3 of 3
date 08/2007
PART NUMBER: VASD1-SIP series
DESCRIPTION: DC/DC converter
- Minimum loading
APPLICATION NOTES:
The converter needs a minimum of 10% loading to maintain
output regulation. Operation under no-load conditions will not
cause immediate damages but may reduce reliability, and
cause performance not to meet specifications.
- 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.
- Regulation
With a semi-regulated design, the converter’s output voltage
varies with load current and will change proportionally to the
input voltage. If regulated output is needed, an external
regulator can be used as shown in Figure 2.
TABLE 1
- 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 also be used to protect against over-loading.
Input Voltage
5 V
External Input Capacitance
4.7 µF
2.2 µF
2.2 µF
1.0 µF
12 V
15 V
- Dual outputs used as a single output
24 V
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.
- Output filtering
An output capacitor is needed to meet output ripple
requirements as shown in Table 2.Output capacitance may be
increased for additional filtering, but should not exeed 10µF or
expanded to an LC network as in Figure 1.
- 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 regulator, 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.
TABLE 2
External Ouput Capacitance
Vout
5 V
4.7 µF
2.2 µF
1.0 µF
9 V
+Vout
+Vin
-Vin
REG
12 V
COM
-Vout
DC DC
15 V
24 V
0.47 µF
0.33 µF
+Vout
REG
REG
+Vin
-Vin
COM
-Vout
DC DC
L
L
+Vout
+Vin
C
COM
C
DC DC
L
C
-Vin
-Vout
<Figure 1>
th
20050 SW 112 Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2382
CUI [ CUI INC ]
