CRE1 Series

Isolated 1W Single Output Isolated DC-DC Converters

KDC_CRE1.D02 Page 7 of 14

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APPLICATION NOTES (continued)

Ripple & Noise Characterisation Method

Ripple and noise measurements are performed with the following test configuration.

C1

1µF X7R multilayer ceramic capacitor, voltage rating to be a minimum of 3 times the output voltage of the DC-DC converter

C2

10µF tantalum capacitor, voltage rating to be a minimum of 1.5 times the output voltage of the DC-DC converter with an ESR of less

than 100mΩ at 100 kHz

C3

100nF multilayer ceramic capacitor, general purpose

R1

450Ω resistor, carbon film, ±1% tolerance

R2

50Ω BNC termination

T1

3T of the coax cable through a ferrite toroid

RLOAD

Resistive load to the maximum power rating of the DC-DC converter. Connections should be made via twisted wires

Measured values are multiplied by 10 to obtain the specified values.

Differential Mode Noise Test Schematic

Output Ripple Reduction

By using the values of inductance and capacitance stated, the output ripple at the rated load is lowered to 5mV p-p max.

Component selection

Capacitor: It is required that the ESR (Equivalent Series Resistance) should be as low as possible, ceramic types are recommended.

The voltage rating should be at least twice (except for 15V output), the rated output voltage of the DC-DC converter.

Inductor: The rated current of the inductor should not be less than that of the output of the DC-DC converter. At the rated current, the DC resistance of the inductor

should be such that the voltage drop across the inductor is <2% of the rated voltage of the DC-DC converter. The SRF (Self Resonant Frequency) should be

>20MHz.

DC

DC

L

C

Load

Power

Source

Inductor

Capacitor

L, µH

SMD

Through Hole

C, µF

CRE1S0505DC

CRE1S0505SC

CRE1S0515SC

CRE1S1205SC

CRE1S1212SC

CRE1S2405SC

CRE1S2412SC

CRE1S0305S3C

CRE1S0505S3C

CRE1S0505MC

47

82473C

11R473C

4.7

CRE1S0505MEC

10

82103C

11R103C

4.7

OSCILLOSCOPE

Y INPUT

SUPPLY

C1 C2 C3

R1

T1

R2

Input

Output

DC/DC Converter

R LOAD

+

+

-

-