®
LSN2 Series
Non-isolated, DOSA-SIP, 6/10/16A Selectable-Output DC/DC Converters
Performance/Functional Specification Notes:
All models are tested and specified with external 1 || 10ꢀF ceramic/tantalum output capacitors
(8)
(1)
Output noise may be further reduced by adding an external filter. See I/O Filtering and Noise
Reduction.
All models are fully operational and meet published specifications, including “cold start” at
–40°C. VOUT is nominal.
Regulation specifications describe the deviation as the line input voltage or output load current is
varied from a nominal midpoint value to either extreme.
Other input or output voltage ranges are available under scheduled quantity special order.
Maximum PC board temperature is measured with the sensor in the center.
Do not exceed maximum power specifications when adjusting the output trim.
When Sequencing is not used, the Power Good output is TRUE at any time the output is within
approximately 10% of the voltage set point. Power Good basically indicates if the converter is
in regulation. Power Good detects Over Temperature if the PWM has shut down due to OT. Power
Good does not directly detect Over Current.
If Sequencing is in progress, Power Good will falsely indicate TRUE (valid) before the output
reaches its setpoint. Ignore Power Good if Sequencing is in transition.
The maximum output capacitive loads depend on the the Equivalent Series Resistance (ESR) of
the external output capacitor.
Do not use Pre-bias startup and sequencing together. See Technical Notes below.
and a 22ꢀF external input capacitor. All capacitors are low ESR types. These capacitors are
necessary to accommodate our test equipment and may not be required to achieve specified
performance in your applications. All models are stable and regulate within spec under no-load
conditions.
General conditions for Specifications are +25°C, VIN = nominal, VOUT = nominal, full load. “Nomi-
nal” output voltage is +5V for D12 models and +3.3V for W3 models.
(9)
(10)
(11)
(12)
(13)
(14)
(2)
Input Back Ripple Current is tested and specified over a 5-20MHz bandwidth. Input filtering is
CIN = 2 x 100ꢀF tantalum, CBUS = 1000ꢀF electrolytic, LBUS = 1ꢀH.
(3)
Note that Maximum Power Derating curves indicate an average current at nominal input voltage.
At higher temperatures and/or lower airflow, the DC/DC converter will tolerate brief full current
outputs if the total RMS current over time does not exceed the derating curve.
(4)
Mean Time Before Failure is calculated using the Telcordia (Belcore) SR-332 Method 1, Case 3,
ground fixed conditions, TPCBOARD = +25°C, full output load, natural air convection.
(5)
The On/Off Control may be driven with external logic or by applying appropriate external voltages
which are referenced to –Input Common. The On/Off Control Input should use either an open
collector/open drain transistor or logic gate which does not exceed +VIN. A 68KΩ external pullup
resistor to +VIN will cause the “ON” state for negative logic models.
(15)
(16)
(17)
(6)
Short circuit shutdown begins when the output voltage under increasing load degrades approxi-
After short circuit shutdown, if the load is partially removed such that the load still exceeds the
overcurrent (OC) detection, the converter will remain in hiccup restart mode.
For best noise performance, leave the Track/Sequence pin OPEN when not used.
mately 2% from the selected setting.
(7)
If Sense is connected remotely at the load, up to 0.5 Volts difference is allowed between the
(18)
Sense and +VOUT pins to compensate for ohmic voltage drop in the power lines. A larger voltage
drop may cause the converter to exceed maximum power dissipation.
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Figure 1. LSN2 Series Simplified Schematic
output capacitors are specified for low ESR and full-range frequency response.
TECHNICAL NOTES
In critical applications, input/output ripple/noise may be further reduced using
filtering techniques, the simplest being the installation of external I/O caps.
I/O Filtering and Noise Reduction
All models in the LSN2 Series are tested and specified with external
1 || 10ꢀF ceramic/tantalum output capacitors and a 22ꢀF tantalum input
capacitor. These capacitors are necessary to accommodate our test equip-
ment and may not be required to achieve desired performance in your appli-
cation. The LSN2's are designed with high-quality, high-performance internal
I/O caps, and will operate within spec in most applications with no additional
external components.
External input capacitors serve primarily as energy-storage devices. They
minimize high-frequency variations in input voltage (usually caused by IR
drops in conductors leading to the DC/DC) as the switching converter draws
pulses of current. Input capacitors should be selected for bulk capacitance
(at appropriate frequencies), low ESR, and high rms-ripple-current ratings.
The switching nature of modern DC/DC's requires that the dc input voltage
source have low ac impedance at the frequencies of interest. Highly inductive
source impedances can greatly affect system stability. Your specific system
configuration may necessitate additional considerations.
In particular, the LSN2's input capacitors are specified for low ESR and are
fully rated to handle the units' input ripple currents. Similarly, the internal
LSN2 Series Page 4 of 14
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