Application Notes
Ultra High Efficiency 82 - 91%
High Efficiency, Small, Low price, Step-Down DC-DC Converter
5 Watt VSA Series
<Usage>
(A) Standard Connection
Recommended Additional Capacitor
VSA05-2.5S1R2
C1=16ZL330M (Rubycon) or KZE16VB330 (Nippon Chemi-con)
C2=10ZL680M (Rubycon) or KZE16VB680 (Nippon Chemi-con)
VSA24-3.3S1R2
C1=50ZL120M (Rubycon) or KZE50VB120（Nippon Chemi-con）
C2=10ZL470M (Rubycon) or KZE10VB470（Nippon Chemi-con）
VSA24-12S0R6
C1=50ZL120M (Rubycon) or KZE50VB120（Nippon Chemi-con）
C2=16ZL330M (Rubycon) or KZE16VB330（Nippon Chemi-con）
Note 1: If ON/OFF is not controlled, it should be connected to
GND line.
Note 2: When output voltage is rating, please open the terminal V. ADJ
( Figure 4 )
(5 pin)
Note 3: I/O capacitor (C1, C2) must be added. Please put I/O capacitor
to pin close as much as possible and wire with thick pattern.
For C1 & C2, please use low impedance capacitor.
Note 4: For VSA05 model, when the additional capacitor's capacity is
large, startup failure may occur. So please use an additional
capacitor which capacity is 8,200µF or below.
(B) ON/OFF Control
Input voltage is turned on by using ON/OFF control function, and it is
possible for ON/OFF control of output voltage without cutting it.
That is the effective function to compose the sequence of Power
Supply Systems. Also using this function, you can save the electric
power when Power Supply stands by. Please connect the terminal
ON/OFF with GND.
Between the terminal ON/OFF (1 Pin) and GND (3 Pin)
VSA05-2.5S1R2
Output voltage OFF mode : OPEN (2V to +Vin)
Output voltage ON mode : SHORT (-0.2 to 0.7V, 10µA)
( Figure 5 )
VSA24-3.3S1R2
Output voltage OFF mode : OPEN (2.5 to 5.3 V)
Output voltage ON mode : SHORT (-0.2 to 0.5 V, 250µA )
VSA24-12S0R6
Output voltage OFF mode : OPEN (2.5 to 5.3 V)
Output voltage ON mode : SHORT (-0.2 to 0.5 V, 250µA )
Note 1: Use an open collector (or drain) switch element for on/ off control.
Note 2: Set the switch element for on/ off control close to the converter, and lessen the noise effect by parallel patern short loops, or by
using shield wires.
To prevent miss operation caused by noise, it is effective to connect a capacitor between the on/ off pin and GND. However, if this
capacitor is too large, when impressing the input voltage at off, the charged current may flow and momentarily voltage may occur,
so be sure that the max. value is 3300pF.
Note 3: The on/ off pin voltage will be pulled up internally, so it is not necessary to impress voltage externally at off.
Kaga Electronics(USA) Inc.
www.volgen.com
Ultra High Efficiency 82 - 91%
High Efficiency, Small, Low price, Step-Down DC-DC Converter
5 Watt VSA Series
(C) Output voltage changeable direction
Please open the terminal V.ADJ when you use the output voltage with
rating, without changing. By connecting resistance between the terminal
GND (3 Pin) and V.ADJ (5 Pin), you can change output voltage within the
range of voltage in Table 1. Please refer to the undermentioned equation
for the calculation of external resistance. Please confirm the output
voltage and adjust resistance value after calculating external resistance.
( Figure 6 )
To reduce the output voltage
Model
VR1 =
Rx×Ry×(Vo-Vref)
Rx×Vref-Ry(Vo-Vref)
Voltage Range
2.5S
(1.5 to 2.5V)
2.13K ohm
1.0K ohm
0.8V
3.3S
(3 to 3.3V)
765 ohm
2.2K ohm
2.45V
12S
(9 to 12V)
8.6K ohm
2.2K ohm
2.45V
VR2 = OPEN
VO = It is your option.
Rx
Ry
Vref
To add the output voltage (for 2.5V and 3.3V model)
VR2 =
Vref×Rx×Ry
Ry(Vo-Vref)-Vref×Rx
Model
Voltage Range
2.5S
(2.5 to 3.3V)
2.13K ohm
1.0K ohm
0.8V
3.3S
(3.3 to 5V)
765 ohm
2.2K ohm
2.45V
12S
N/ A
Rx
Ry
Vref
VR1 = OPEN
VO = It is your option.
Note 1: When using at rating without adjusting the output voltage, keep
the V. ADJ pin (5pin) open.
Note 2: V. ADJ pin (5pin) is a high impedance point, so in a bad environment
this wiring may pick up noise and cause bad effect. When
energizing, avoid switching the output by opening and shortening
or switching the adjustable output resistor(R1, R2). And select a
R1, R2 that is accurate and has good temperature characteristics,
and mount it by soldering without using connectors or sockets
when it is pretty close to the converter.
Kaga Electronics(USA) Inc.
www.volgen.com
Ultra High Efficiency 82 - 91%
High Efficiency, Small, Low price, Step-Down DC-DC Converter
Note: These test data do not represent all products.
<Turn-On transient>
<Output Ripple & Noise>
5 Watt VSA Series
VSA05-2.5S1R2
VSA05-2.5S1R2
Vout
0.5V/div
V: 10mV/div
Vin: 0V
Vout: 0V
Vin: ON
t:2msec/div
Vin
5V/div
t:1µsec/div
Test conditions: Rating input/Rating load/Room temperature
Test conditions: Rating input/Rating load/Room temperature
VSA24-3.3S1R2
Output
3.3V 1.2A
3.3V
VSA24-3.3S1R2
Output Voltage
1V/div
0V
V: 50mV/div
24V
Input Voltage
10V/div
0V
On
1ms/div
50mV/div
t:2µsec/div
Test conditions: Rating input/Rating load/Room temperature
Test conditions: Rating input/Rating load/Room temperature
VSA24-12S0R6
Output
12V 0.55A
12V
Output Voltage
0V
5V/div
VSA24-12S0R6
V: 50mV/div
24V
Input Voltage
10V/div
0V
On
2ms/div
50mV/div
t:2µsec/div
Test conditions: Rating input/Rating load/Room temperature
Test conditions: Rating input/Rating load/Room temperature
Kaga Electronics(USA) Inc.
www.volgen.com
Ultra High Efficiency 82 - 91%
High Efficiency, Small, Low price, Step-Down DC-DC Converter
5 Watt VSA Series
<Temperature derating>
Please set this products at good place for the convection.
As to Temperature derating and air condition, please see the below.
Cooling Condition : Natural Air Cooling
1.4
1.2
1
0.8
0.6
0.4
0.2
0
-30 -20 - 10
VSA05-2.5S1R2
起 動 可
Possible Start-up Range
0
10
20
30
40
50
60
70
80
VSA24-3.3S1R2
1.4
1.2
Load Current (A)
1.0
0.8
0.6
0.4
0.2
0
-30 -20
-10
0
10
20
Operating Range
Possible Start-up Range
Vin=9V
Vin=24V
0.5A
Vin=36V
30
40
50
60
70
80
Ambient Temperature (°C)
VSA24-12S0R6
0.6
0.5
0.4
0.3
0.2
0.1
0
-30 -20
Vin=18,24V
Operating Range
Possible Start-up Range
Load Current (A)
Vin=36V
-10
0
10
20
30
40
50
60
70
80
Ambient Temperature (°C)
Kaga Electronics (USA) Inc.
www.volgen.com
Ultra High Efficiency 82 - 91%
High Efficiency, Small, Low price, Step-Down DC-DC Converter
5 Watt VSA Series
<Over-Current Protection>
This model has a built-in over-current protection circuit (operating at rating 105% or more), and protects against
the output over-current.
It will automatically recover by releasing the over-current condition. Please avoid keeping long-time over-current or
output short-circuit condition, it may cause converter's failure. For a protection in case a large current flows into
the input, caused by the converter's failure, be sure to connect a fuse to the input +line.
VSA05 Series
1) Over-Current Protection
The over-current characteristics are as you can see in figure 7, and will automatically recover by releasing
the over-current condition. However, when the load impedance comes close to 0 and the current grows,
the latch circuiit may operate. When the latch circuit operates, release the over-current condition and restart
the input.
Output Voltage(V)
Output Current (A)
2) Output Short-Circuit Protection
(Figure 7)
The over-current protection will also operate when the output is short. However, when the output suddenly
goes short, or restart the input when the output is still short, a very large current will flow into the converter
momentarily and the over-current point may grow due to the short-circuit current.
For a protection in case the output goes short or the load failure causes an output short-circuit condition, be
sure to connect a fuse.
VSA24 Series
The over-current characteristics are as you can see in figure 8, and will automatically recover by releasing
the over-current condition.
Output Voltage (V)
Output Current (A)
(Figure 8)
Kaga Electronics (USA) Inc.
www.volgen.com
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