Technical Specification
Non-Isolated
SIP Converter
3.0 - 3.6V
15A
in
output voltage too high may cause the over-voltage protection
circuit to engage, particularly during transients.
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.
Total DC Variation of Vout: For the converter to meet its
specifications, the maximum variation of the DC value of Vout,
due to both trimming and remote load voltage drops, should
not be greater than that specified for the output voltage trim
range.
PROTECTION FEATURES
APPLICATION CONSIDERATIONS
Input Under-Voltage Lockout: The converter is designed
to turn off when the input voltage is too low, helping avoid an
input system instability problem, described in more detail in the
application note titled “Input System Instability”. The lockout cir-
cuitry is a comparator with DC hysteresis. When the input volt-
age is rising, it must exceed the typical Turn-On Voltage
Threshold value (listed on the specification page) before the
converter will turn on. Once the converter is on, the input volt-
age must fall below the typical Turn-Off Voltage Threshold value
before the converter will turn off.
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.
Over Current Shutdown: The converter uses the control
(high-side) MOSFET on-resistance to detect short circuit or
excessive over-current conditions. The converter compensates
for the temperature variation of the MOSFET on-resistance,
keeping the overcurrent threshold roughly constant over tem-
perature. Very short (<1mS) over-current pulses will see a
slightly higher apparent threshold than longer duration over-
current events. This makes the converter less susceptible to
shutdown from transient load conditions. However, once the
over-current threshold is reached the converter ceases PWM
operation within microseconds. After an over-current shut-
down, the converter will remain off for an inhibit period of 18
to 32 milliseconds, and then attempt a soft-start. Depending on
the impedance or current level of the overload condition, the
converter will enter a "hiccup mode" where it repeatedly turns
on and off at a frequency of 25 to 50 Hz, until the overload or
short circuit condition is removed.
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 40
tance. At 300 kHz., the impedance of the internal capacitance
is about 15mΩ capacitive. At that frequency, an SMT 330
µF internal ceramic capaci-
µF
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
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 uses the OVP threshold of the 2.5V unit.
that capacitor would reduce the ripple current to about 1.5A,
o
probably within its rating at 85 C. 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 a 1.5V or higher output voltage, or
on lower voltage outputs when trimming down by more than
Product # NQ03xxxVMA15
Phone 1-888-567-9596
Doc.# 005-2NV3xxE Rev. E
6/24/04
Page 14
SYNQOR [ SYNQOR WORLDWIDE HEADQUARTERS ]
