TEST CONFIGURATIONS
DESIGN CONSIDERATIONS
TO OSCILLOSCOPE
Input Source Impedance
L
To maintain low-noise and ripple at the input voltage, it is
critical to use low ESR capacitors at the input to the
module. The input capacitance should be able to handle
an AC ripple current of at least:
VI(+)
100uF
Tantalum
2
BATTERY
V(-)
I
Vout
Vin
Vout
Vin
⎛
⎜
⎞
⎟
Irms = Iout
1 −
Arms
⎝
⎠
Note: Input reflected-ripple current is measured with a
simulated source inductance. Current is measured at
the input of the module.
The power module should be connected to a low
ac-impedance input source. Highly inductive source
impedances can affect the stability of the module. An
input capacitance must be placed close to the modules
input pins to filter ripple current and ensure module
stability in the presence of inductive traces that supply
the input voltage to the module.
Figure 19: Input reflected-ripple test setup
COPPER STRIP
Vo
Safety Considerations
Resistive
Load
1uF
10uF
tantalum ceramic
SCOPE
For safety-agency approval the power module must be
installed in compliance with the spacing and separation
requirements of the end-use safety agency standards.
GND
For the converter output to be considered meeting the
requirements of safety extra-low voltage (SELV), the
input must meet SELV requirements. The power module
has extra-low voltage (ELV) outputs when all inputs are
ELV.
Note: Use a 10µF tantalum and 1µF capacitor. Scope
measurement should be made using a BNC connector.
Figure 20: Peak-peak output noise and startup transient
measurement test setup
The input to these units is to be provided with a
maximum (TBD) A of glass type fast-acting fuse in the
ungrounded lead.
CONTACT AND
DISTRIBUTION LOSSES
VI
Vo
I
Io
LOAD
SUPPLY
GND
CONTACT RESISTANCE
Figure 21: Output voltage and efficiency measurement test
setup
Note: All measurements are taken at the module terminals.
When the module is not soldered (via socket), place
Kelvin connections at module terminals to avoid
measurement errors due to contact resistance.
Vo× Io
Vi × Ii
η = (
)×100 %
DS_DNT12SMD03_06252007
6
DELTA [ DELTA ELECTRONICS, INC. ]
