AN1695 - APPLICATION NOTE

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2.2 Performances

As explained in the datasheet, the step-down converter using TSM108 can feature an accurate

constant-voltage and constant-current regulation. The V/I output characteristics of the DC/DC converter is

shown in Figure 4. Input voltage was set at 12V during this test. As explained in introduction, voltage

regulation is set to 6V and current regulation is set to 800mA. At output voltage lower than 1V, the

foldback can be observed in the current regulation.

Figure 4 : Output voltage versus output current characteristics

The efficiency of the DC/DC converter was measured in different conditions, as shown in Figure 5.

On the left chart, the influence of output power (Pout) over efficiency is studied. It should be noted that

during this test, the converter was operating in constant-voltage mode, therefore with Vout=6V and

Iout<800mA. Input voltage Vin was equal to 12V during the test. The efficiency appears to be always

between 84% and 90%.

On the right chart, the influence of input voltage (Vin) over efficiency is studied. The converter was

operating in constant-voltage mode and the output power was constant equal to 4W during the test. With

the input voltage varying from 7V up to 25V, the converter efficiency appears to be between 84% and

90%.

Figure 5 : Efficiency of the DC/DC converter versus output power and input voltage

0

1

2

3

4

5

6

7

0

100

200

300

400

500

600

700

800

900

Iout (mA)

Efficiency vs. Output Power @ Vout=6V Vin=12V

82%

84%

86%

88%

90%

92%

94%

0

1000

2000

3000

4000

Pout (mW)

Efficiency vs. Input Voltage @ Vout=6V Pout=4,0W

82%

84%

86%

88%

90%

92%

94%

510

15

20

25

Vin (V)