BXA15 Datasheet, PDF (3/4 Pages) Artesyn Technologies – Design Note 100 Rev. 01 - Feb. 1999

Design Note 100 Rev. 01 | BXA15 AND BXA30 SERIES
It is imperative to account for both the resistive and reactive compo-
nents of source impedance.
The input operating voltage range specified refers to the voltage
which must be maintained across the inputs pins, during all steady
state and transient conditions. Models without the internal filter
option will generally require a much lower reactive source imped-
ance than for those with the internal filter installed. This is because
the input current will have large harmonics at the DC/DC converter
switching frequency.
The reactive source impedance can be effectively reduced by
adding local film or ceramic capacitors. A recommended film
capacitor is ITW Paktron 20µF, 50 Volts Capstick or equivalent.
(ITW Paktron Part Number: 206K050CS4).
Local Decoupling of High Frequency Input Ripple Current:
This is particularly important for 12Vin models. Non filter versions
have a maximum input current of 5 Amps DC with 0.7A ACrms
superimposed. The AC current is almost sinusoidal and at 350 -
400kHz. The source impedance must be able to supply this current
with negligible voltage ripple. Adding the recommended film capac-
itor across the input pins will allow the high frequency input current
requirement to be locally sourced. This will also dramatically reduce
both input conducted noise and radiated noise.
Start-up Surge Consideration:
Depending on lead inductance and source impedance a higher
value, parallel, ‘reservoir’ electrolytic may be required to ensure ade-
quate input voltage is maintained during start-up and transients.
The start-up surge current is always well within ETSI limits but is still
significant and the source must be able to supply it with low
dropout. During this surge the input voltage should remain above
the minimum on threshold.
IR Steady State Voltage Drop Consideration:
Care must be taken with lead and connector resistances. The
source voltage should be a minimum of 9 Volts + R (total, leads +
connectors).
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