TEST CONFIGURATIONS
TO OSCILLOSCOPE
DESIGN CONSIDERATIONS
Input Source Impedance
V
I
(+)
To maintain low noise and ripple at the input voltage, it is
critical to use low ESR capacitors at the input to the
module. Figure 32 shows the input ripple voltage (mVp-p)
for various output models using 2x100 µF low ESR
tantalum
capacitor (KEMET p/n: T491D107M016AS,
AVX p/n: TAJD107M106R, or equivalent) in parallel with
47 µF ceramic capacitor (TDK p/n:C5750X7R1C476M or
equivalent). Figure 33 shows much lower input voltage
ripple when input capacitance is increased to 400 µF (4 x
100 µF)
tantalum
capacitors in parallel with 94 µF (2 x 47
µF) ceramic capacitor.
The input capacitance should be able to handle an AC
ripple current of at least:
L
2
100uF
Tantalum
BATTERY
V
I
(-)
Note: Input reflected-ripple current is measured with a
simulated source inductance. Current is measured at
the input of the module.
Figure 29:
Input reflected-ripple test setup
COPPER STRIP
Irms
=
Iout
Input Ripple Voltage (mVp-p)
200
150
100
50
0
0
Vout
⎛
Vout
⎞
⎜
1
−
⎟
Vin
⎝
Vin
⎠
Arms
Vo
1uF
10uF
SCOPE
tantalum ceramic
Resistive
Load
GND
3.3Vin
5.0Vin
1
2
Output Voltage (Vdc)
3
4
Note: Use a 10µF tantalum and 1µF capacitor. Scope
measurement should be made using a BNC connector.
Figure 30:
Peak-peak output noise and startup transient
measurement test setup.
CONTACT AND
DISTRIBUTION LOSSES
Figure 32:
Input voltage ripple for various output models, Io =
6A (CIN = 2
×
100µF tantalum // 47µF ceramic)
V
I
I
I
SUPPLY
Vo
LOAD
80
Input Ripple Voltage (mVp-p)
Io
60
40
20
0
0
1
2
Output Voltage (Vdc)
GND
CONTACT RESISTANCE
3.3Vin
5.0Vin
Figure 31:
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.
3
4
Figure 33:
Input voltage ripple for various output models, Io =
6A (CIN = 4
×
100µF tantalum // 2
×
47µF ceramic)
η
=
(
Vo
×
Io
)
×
100 %
Vi
×
Ii
DS_DNS04SMD6A_10202006
8
DELTA [ DELTA ELECTRONICS, INC. ]
