MDC_LSN W3 Models.A01 Page 7 of 8

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Single Output LSN-W3 Models

16 Amp DC/DC Converters

LSN W3 DC/DC converters do not suffer from Output Reverse Conduction.

They employ proprietary gate drive circuitry that makes them immune to

moderate applied output overvoltages.

Thermal Considerations and Thermal Protection

The typical output-current thermal-derating curves shown below enable

designers to determine how much current they can reliably derive from each

model of the LSN W3 Series under known ambient-temperature and air-flow

conditions. Similarly, the curves indicate how much air flow is required to reli-

ably deliver a specific output current at known temperatures.

The highest temperatures in LSN W3’s occur at their output inductor, whose

using thermocouples to monitor the inductor temperature and varying the load

to keep that temperature below +110°C under the assorted conditions of air

flow and air temperature. Once the temperature exceeds +115°C (approx.), the

thermal protection will disable the converter. Automatic restart occurs after the

temperature has dropped below +110°C.

As you may deduce from the derating curves and observe in the efficiency

curves on the following pages, LSN W3’s maintain virtually constant efficiency

from half to full load, and consequently deliver very impressive temperature

performance even if operating at full load.

Lastly, when LSN W3’s are installed in system boards, they are obviously

subject to numerous factors and tolerances not taken into account here. If you

are attempting to extract the most current out of these units under demanding

temperature conditions, we advise you to monitor the output-inductor tempera-

ture to ensure it remains below +110°C at all times.

20 Amps Extended Operation

Under restricted conditions, the LSN W3 models with low output voltages

may produce up to 20 Amps of output current up to approximately +45°C

ambient temperature. There is no model number change. The Derating

curve illustrates typical performance. For this test, the converter was

mounted on a 12cm x12cm double-sided pc board with 2 ounce copper.

This 20 Amp operation is available with the following restrictions:

• Only 1.2 Volt and 1.5 Volt output models are verified for operation at

this time.

• The user must assure that there is adequate airflow at all times with

no airflow blockage by other large components. Make sure no adjacent

components have high temperatures. Be aware of systems using a

CPU temperature monitor to control the fan.

• Use only low to moderate ambient temperature.

• The user must assure that the total output power is not exceeded.

• This operation applies only to nominal input line voltage. Since effi-

ciency degrades at low line voltage, internal heat dissipation increases,

thereby exceeding the maximum output power.

The Derating curve is drawn where the hot spot on the converter (usually

a power FET) reaches approximately +115°C. Although operation is possible

slightly beyond this point, DATEL strongly advises using this as the maxi-

mum temperature for greatest reliability.

Do not forget that a small overcurrent glitch while running 20 Amps output

could instantly shut down the converter using the Over Current sensor. This

margin of safety is considerably wider at 16 Amps maximum current. Make

sure your output current usage is smooth!! If you are in doubt, contact DATEL

to discuss your application.