Figure 1. LSN2 Series Simplified Schematic

®

LSN2 Series

Non-isolated, DOSA-SIP, 6/10/16A Selectable-Output DC/DC Converters

www.cd4power.com

Performance/Functional Specification Notes:

(1)

All models are tested and specified with external 1 || 10μF ceramic/tantalum output capacitors

and a 22μF 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.

nal” output voltage is +5V for D12 models and +3.3V for W3 models.

(2)

Input Back Ripple Current is tested and specified over a 5-20MHz bandwidth. Input filtering is

(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,

(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

Ω external pullup

(6)

Short circuit shutdown begins when the output voltage under increasing load degrades approxi-

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

drop may cause the converter to exceed maximum power dissipation.

I/O Filtering and Noise Reduction

All models in the LSN2 Series are tested and specified with external

1 || 10μF ceramic/tantalum output capacitors and a 22μF 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.

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

TECHNICAL NOTES

(8)

Output noise may be further reduced by adding an external filter. See I/O Filtering and Noise

Reduction.

(9)

All models are fully operational and meet published specifications, including “cold start” at

(10)

Regulation specifications describe the deviation as the line input voltage or output load current is

varied from a nominal midpoint value to either extreme.

(11)

Other input or output voltage ranges are available under scheduled quantity special order.

(12)

Maximum PC board temperature is measured with the sensor in the center.

(13)

Do not exceed maximum power specifications when adjusting the output trim.

(14)

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.

(15)

The maximum output capacitive loads depend on the the Equivalent Series Resistance (ESR) of

the external output capacitor.

(16)

Do not use Pre-bias startup and sequencing together. See Technical Notes below.

(17)

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.

(18)

For best noise performance, leave the Track/Sequence pin OPEN when not used.

output capacitors are specified for low ESR and full-range frequency response.

In critical applications, input/output ripple/noise may be further reduced using

filtering techniques, the simplest being the installation of external I/O caps.

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.