NQ04T33VMA16 Datasheet, PDF (17/20 Pages) SynQor Worldwide Headquarters – On-board input and output filter capacitor

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Non-Isolated
SIP Converter
3.0 - 5.5Vin 16A
and off at a frequency of 25 to 50 Hz, until the overload or
short circuit condition is removed.
Output Over-Voltage Limit: If the voltage across the output
pins exceeds the Output Over-Voltage Protection threshold, the
converter will immediately stop switching. This prevents dam-
age to the load circuit due to 1) excessive series resistance in
output current path from converter output pins to sense point, 2)
a release of a short-circuit condition, or 3) a release of a cur-
rent limit condition. Load capacitance determines exactly how
high the output voltage will rise in response to these conditions.
After 2-4 ms, the converter will automatically restart. Note the
wide trim model has a typical OVP threshold of 4.1V.
Over-Temperature Shutdown: A temperature sensor on
the converter senses the average temperature of the module.
The thermal shutdown circuit is designed to turn the converter
off when the temperature at the sensed location reaches the
Over-Temperature Shutdown value. It will allow the converter to
turn on again when the temperature of the sensed location falls
by the amount of the Over-Temperature Shutdown Restart
Hysteresis value.
APPLICATION CONSIDERATIONS
Input and Output Filtering: SynQor recommends an exter-
nal input capacitor of either a tantalum, polymer or aluminum
electrolytic type on the input of the NQ03/NQ04 series non-
isolated converters. This capacitance and resistance primarily
provides damping of the input filter, reduces the source imped-
ance and guarantees input stability (see SynQor application
note "Input System Instability"). The input filter is formed by any
source or wiring inductance and the converter’s input capaci-
tance. The external capacitance also provides an additional
benefit of ripple voltage reduction.
A modest sized capacitor would suffice in most conditions, such
as a 330µF, 16V tantalum, with an ESR of approximately 50
mΩ. The NiQor family converters have an internal ceramic
input capacitor to reduce ripple current stress on the external
capacitors. An external ceramic capacitor of similar size
(330µF) with a series resistor of approximately 50 mΩ would
also suffice and would provide the filter damping.
Additional ceramic capacitance may be needed on the input,
in parallel with the tantalum capacitor, to relieve ripple current
stress on the tantalum capacitors. The external capacitance
forms a current divider with the 40µF internal ceramic capaci-
tance. At 300 kHz., the impedance of the internal capacitance
is about 15mΩ capacitive. At that frequency, an SMT 330µF
tantalum capacitor would have an impedance of about 50mΩ
resistive, essentially just the ESR.
In this example, at full load, that would stress the tantalum input
capacitor to about 3A rms ripple current, possibly beyond its
rating. Placing an additional 40µF of ceramic in parallel with
that capacitor would reduce the ripple current to about 1.5A,
probably within its rating at 85^oC. The input ripple current is
proportional to load current, so this example should be scaled
down according to the actual load current.
Additional input capacitance equal to half of the output capac-
itance is recommended when operating with more than 1000uF
of output capacitance on lower voltage outputs when trimming
down by more than half of the trim-down allowance (e.g., fur-
ther than -2.5% on a 0.9V, or -5% on a 1.2V).
Input inductance should be reduced for maintaining input sta-
bility when operating with large output capacitance
(>1000µF). Reducing input inductance to <0.3µH provides for
good phase margin with up to the 4000µF maximum output
capacitance. If the input inductance must be increased up to
1µH even with large output capacitance (>1000µF), an input
capacitance equal to or greater than the output capacitance
may be needed to compensate the input impedance.
If no inductor is used to isolate the input ripple of the NiQor
converters from the source or from inputs of other NiQor con-
verters, then this external capacitance might be provided by the
DC/DC converter used as the power source. SynQor's
PowerQor series converters typically have tantalum and ceram-
ic output capacitors that would provide the damping.
An input inductor would help isolate the ripple currents and
voltages from the source or other NiQor style converters on the
voltage supply rail. If an input inductor is used, the recom-
mended capacitance should guarantee stability and control the
ripple current for up to 1.0µH of input inductance.
The input inductor need not have very high inductance. A
value of 250 nanohenries would equate to almost 500 miliohm
of series impedance at the switching frequency of 300 kHz.
This would be working against an assumed capacitive ESR of
30mΩ on the supply side of the inductor, providing significant
isolation and ripple reduction.
No external capacitance is required at the output, however, the
ripple voltage can be further reduced if ceramic and tantalum
capacitors are added at the output. Since the internal output
capacitance is about 50µF, approximately that amount of
ceramic capacitance would be needed to produce a noticeable
reduction in output ripple. The value of the tantalum capacitors
is both to provide a high capacitance for pulsed loads and to
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