+INPUT
(7,8)
COMMON
(6)
PWM
CONTROLLER
CURRENT
SENSE
REFERENCE &
ERROR AMP
VCC
ON/OFF
CONTROL
(11)
VOUT
TRIM
(10)
+OUTPUT
(1,2,4)
330µF100µF
66µF
10.5Ω
+SENSE
(3)
COMMON
(5)
Single Output
LSN-16A D12 Models
Features
Non-Isolated, 12VIN, 0.75-5VOUT
16 Amp DC/DC’s in SIP Packages
Figure 1. Simplified Schematic
LSN Series D12 SIP's (single-in-line packages) are ideal building blocks for
emerging, on-board power-distribution schemes in which isolated 12V buses deliver
power to any number of non-isolated, step-down buck regulators. LSN D12 DC/DC's
accept a 12V input (10V to 14V input range) and convert it, with the highest effi-
ciency in the smallest space, to a 0.75, 1, 1.2, 1.5, 1.8, �2.5, 3.3 or 5 Volt output fully
rated at 16 Amps.
LSN D12's are ideal point-of-use/load power processors. They typically require
no external components. Their vertical-mount packages occupy a mere 0.72 square
inches (4.6 sq. cm), and reversed pin vertical mount allows mounting to meet
competitor's keep out area. Horizontal-mount packages ("H" suffix) are only 0.37
inches (9.4mm) high.
The LSN's best-in-class power density is achieved with a fully synchronous,
fixed-frequency, buck topology that also delivers: high efficiency (96% for 5VOUT
models), low noise (30 to 55mVp-p typ.), tight line/load regulation (±0.1%/±0.25%
max.), quick step response (100µsec), stable no-load operation, and no output
reverse conduction.
The fully functional LSN’s feature output overcurrent detection, continuous
short-circuit protection, an output-voltage trim function, a remote on/off control pin
(pull high to disable), thermal shutdown and a sense pin. High efficiency enables
the LSN D12's to deliver rated output currents of 16 Amps at ambient temperatures
to +68°C with 200 lfm air flow.
If your new system boards call for three or more supply voltages, check out the
economics of on-board 12V distributed power. If you don't need to pay for multiple
isolation barriers, DATEL's non-isolated LSN D12 SIP's will save you money.
■
■
■
■
■
■
■
■
■
■
■
Step-down buck regulators for new
distributed 12V power architectures
12V input (10-14V range)
0.75/1/1.2/1.5/1.8/2.5/3.3/5VOUT @16A
Voltage-selectable "T" version
Non-isolated, fixed-frequency,
synchronous-rectifier topology
Outstanding performance:
• ±1.25% setpoint accuracy
• Efficiencies to 96% @ 16 Amps
• Noise as low as 30mVp-p
• Stable no-load operation
• Trimmable output voltage
Remote on/off control and sense
Thermal shutdown
No derating to +68°C with 200 lfm
UL/IEC/EN60950 certified
EMC compliant
DATEL, Inc., Mansfield, MA 02048 (USA) · Tel: (508)339-3000, (800)233-2765 Fax: (508)339-6356 · Email: sales@datel.com · Internet: www.datel.com
®®
A SUBSIDIARY OF C&D TECHNOLOGIES
LSN-16A D12 Series N O N - I S O L A T E D , 1 3 - 8 0 W S I P D C / D C C O N V E R T E R S
2
MECHANICAL SPECIFICATIONS
Case B8
Vertical Mounting
(Standard)
PART NUMBER STRUCTURE
0.37
(9.4)
0.21
(5.33)
0.16
(4.06)
0.360
(9.14)
1 2 3 4 5 76 8 9
ISOLATING
PAD
10 11
2.00
(50.80)
0.030 ±0.001 DIA.
(0.762 ±0.025)
0.50
(12.7)
0.05
(1.27)
0.05
(1.27)
0.50
(12.7)
0.45
(11.43)
0.400
(10.16)
0.56
(14.22)
0.53
(13.46)
4 EQ. SP. @
0.100 (2.54)
0.500
(12.70)
5 EQ. SP. @
0.100 (2.54)
1.000
(25.40)
LAYOUT PATTERN
TOP VIEW
RECOMMENDED
COPPER PAD
ON PCB (0.55 SQ. IN.)
Case B8A
Horizontal Mounting
Performance Specifications and Ordering Guide ➀
LAYOUT PATTERN
TOP VIEW
0.37
(9.4)
0.20
(5.08)
0.13
(3.3)
0.07
(1.8)
0.37
(9.4)
0.32
(8.13)
1 2 3 4 5 76 8 9 10 11
2.00
(50.80)
0.030 ±0.001 DIA.
(0.762 ±0.025)
0.50
(12.7)
0.05
(1.27)
0.400
(10.16)
4 EQ. SP. @
0.100 (2.54)
0.500
(12.70)
5 EQ. SP. @
0.100 (2.54)
1.000
(25.40)
0.17
(4.32)
Case B8B
Reverse Pin
Vertical Mounting
(Tyco-compatible)
Pin Function P59 Pin Function P59 Pin Function P59
1 +Output 5 Common 9 No Pin
2 +Output 6 Common 10 VOUT Trim
3 +Sense 7 +Input 11 On/Off Control
4 +Output 8 +Input
I/O Connections
Maximum Rated Output
Current in Amps
Non-Isolated SIP
Output
Configuration:
L = Unipolar
Low Voltage
Nominal Output Voltage:
0.75, 1, 1.2, 1.5, 1.8, 2.5, 3.3
or 5 Volts or "T" selectable voltage Input Voltage Range:
D12 = 10-14 Volts
(12V nominal)
L SN -/D12-1.8 H
H Suffix:
Horizontal Mount
J
J Suffix:
Reversed Pin
Vertical Mount
Dimensions in inches (mm)
16
➀ Typical at TA = +25°C under nominal line voltage and full-load conditions, unless noted. All
models are tested and specified with external 22µF tantalum input and output capacitors.
These capacitors are necessary to accommodate our test equipment and may not be required
to achieve specified performance in your applications. See I/O Filtering and Noise Reduction.
➁ Ripple/Noise (R/N) is tested/specified over a 20MHz bandwidth and may be reduced with
external filtering. See I/O Filtering and Noise Reduction for details.
➂ These devices have no minimum-load requirements and will regulate under no-load conditions.
Regulation specifications describe the output-voltage deviation as the line voltage or load is
varied from its nominal/midpoint value to either extreme.
➃ Nominal line voltage, no-load/full-load conditions.
➄ Contact DATEL for availablilty.
➅ LSN-T16-D12 efficiencies are shown at 5V out.
Model
VOUT
(Volts)
IOUT
(Amps)
Max.
Power
(Watts)
R/N (mVp-p)
Typ. Max.
Regulation (Max.)
Line Load
VIN Nom.
(Volts)
Range
(Volts)
IIN
(mA/A)
Full Load ½ Load
Min. Typ. Typ.
Package
(Case
Pinout)
LSN-0.75/16-D12 ➄0.75 16 12.8 45 65 ±0.1% ±0.25% 12 10-14 39/1.21 80% 82.5% 86% B8/B8x, P59
LSN-1/16-D12 1 16 16 45 65 ±0.1% ±0.25% 12 10-14 39/1.45 83% 86% 86% B8/B8x, P59
LSN-1.2/16-D12 1.2 16 19.2 45 60 ±0.1% ±0.25% 12 10-14 45/1.70 85% 89.5% 90% B8/B8x, P59
LSN-1.5/16-D12 1.5 16 24 30 45 ±0.1% ±0.25% 12 10-14 54/2.09 86% 88% 91% B8/B8x, P59
LSN-1.8/16-D12 1.8 16 28.8 30 45 ±0.1% ±0.25% 12 10-14 53/2.49 87% 90.5% 92% B8/B8x, P59
LSN-2.5/16-D12 2.5 16 40 35 50 ±0.1% ±0.25% 12 10-14 60/3.38 90.5% 92.5% 94% B8/B8x, P59
LSN-3.3/16-D12 3.3 16 52.8 40 55 ±0.1% ±0.25% 12 10-14 69/4.37 92.5% 94.5% 96% B8/B8x, P59
LSN-5/16-D12 5 16 80 50 75 ±0.1% ±0.25% 12 10-14 75/6.52 94% 96% 95.5% B8/B8x, P59
LSN-T/16-D12 ➅0.75-5 16 80 55 75 ±0.1% ±0.25% 12 10-14 80/7.0 95% 95.5% 96.5% B8/B8x, P59
Output Input Efficiency
Physical
Outline Dimensions See Mechanical Specifications
Pin Dimensions/Material 0.03" (0.76mm) round copper with tin-lead
plate over nickel underplate
Weight 0.3 ounces (9g)
Flammability Rating UL94V-0
EMI Conducted and Radiated FCC Part 15, EN55022 may require
external filter
Safety UL/cUL 60950, CSA-C22.2 No.234
IEC/EN 60950
LSN-16A D12 Models
N O N - I S O L A T E D , 1 3 - 8 0 W S I P D C / D C C O N V E R T E R S
3
Performance/Functional Specifications
Typical @ TA = +25°C under nominal line voltage and full-load conditions unless noted. ➀
TECHNICAL NOTES
Input Voltage:
Continuous or transient 14Vdc maximum
On/Off Control (Pin 11) +VIN
Input Reverse-Polarity Protection None
Output Overvoltage Protection None
Output Current Current limited. Devices can
withstand sustained output short
circuits without damage.
Storage Temperature –55 to +125°C
Lead Temperature (soldering, 10 sec.) +300°C, 10 seconds maximum.
Refer to solder profile.
These are stress ratings. Exposure of devices to any of these conditions may adversely
affect long-term reliability. Proper operation under conditions other than those listed in the
Performance/Functional Specifications Table is not implied.
Absolute Maximum Ratings
Return Current Paths
The LSN D12 SIP’s are non-isolated DC/DC converters. Their two Common
pins (pins 5 and 6) are connected to each other internally (see Figure 1). To
the extent possible (with the intent of minimizing ground loops), input return
current should be directed through pin 6 (also referred to as –Input or
Input Return), and output return current should be directed through pin 5
(also referred to as –Output or Output Return). Any on/off control signals
applied to pin 11 (On/Off Control) should be referenced to Common
(specifically pin 6).
I/O Filtering and Noise Reduction
All models in the LSN D12 Series are tested and specified with external
22µF tantalum input and output capacitors. These capacitors are necessary
to accommodate our test equipment and may not be required to achieve?
desired performance in your application. The LSN D12'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.
Input
Input Voltage Range 10-14 Volts (12V nominal)
Input Current:
Normal Operating Conditions See Ordering Guide
Standby/Off Mode 5.7mA
Output Short-Circuit Condition 30-60mA
Input Reflected Ripple Current ➁ 30-100mAp-p
Input Filter Type Capacitive
Start-Up Voltage 9 Volts
Overvoltage Protection None
Reverse-Polarity Protection None
Undervoltage Shutdown 8 Volts
No-load Input Current 50-80mA
Remote On/Off Control ➄
–Negative Logic ON = no connection or open
(internal pull down), 0 to +0.4V
OFF = +2.8V to +VIN or pulled high
Remote Control On/Off Current 3mA maximum
Output
Voltage Output Accuracy (50% load) ±1.25% maximum
Minimum Loading ➀ No minimum load
Maximum Output Power See Ordering Guide
VOUT x IOUT must not exceed max. power
Maximum Capacitive Loading 2,000µF (low ESR, OSCON) or
10,000µF (electrolytic)
VOUT Trim Range ±10%
Sense Input Range +10% of VOUT
Ripple/Noise (20 MHz bandwidth) See Ordering Guide
Total Accuracy ±3% over line, load and temperature
Efficiency See Ordering Guide
Overcurrent Detection and
Short Circuit Protection
Current-limiting Detection 23-29 Amps
Short Circuit Detection 98% of VOUT setting ➅
Short Circuit Protection Method Hiccup with autorecovery
See Technical Notes
Short Circuit Current 270-600mA (model dependent)
Short Circuit Duration Continuous, output shorted to ground
Temperature Coefficient ±0.02% per °C
Dynamic Characteristics
Transient Response
(50 to 100% load step to ±2% of Vout) 50µsec typical, 100µsec maximum
Start-Up Time On/Off to VOUT 20msec for VOUT = nominal
Switching Frequency 230-370kHz (model dependent)
Environmental
Calculated MTBF ➃ TBD Hours
Operating Temperature: (Ambient)
No derating, vertical mount –40 to +53°C, natural convection
With derating See derating curves
Storage Temperature Range –55 to +125°C
Thermal Protection/Shutdown 115°C
Density Altitude 0 to 10,000 feet
Relative Humidity 10% to 90%, non-condensing
➀ All models are tested and specified with external 22µF tantalum input and output capacitors.
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.
➁ Input Ripple Current is tested and specified over a 5-20MHz bandwidth. Input filtering is
CIN = 200µF, CBUS = 1000µF, LBUS = 1µH.
➂ Current limit inception is given at either cold start-up or after warm-up.
➃ Mean Time Before Failure is calculated using the Telcordia (Bellcore) SR-332 Method 1, Case 3,
ground fixed conditions, TCASE = +25°C, full load, natural convection, +67°C max. PCB temp.
➄ The On/Off Control (pin 11) may be driven with open-collector logic or by applying appropriate
external voltages which are referenced to Common, pins 5 and 6.
➅ Short circuit shutdown begins when the output voltage degrades approximately 2% from the
selected setting.
LSN-16A D12 Series N O N - I S O L A T E D , 1 3 - 8 0 W S I P D C / D C C O N V E R T E R S
4
Safety Considerations
LSN D12 SIP's are non-isolated DC/DC converters. In general, all DC/DC's
must be installed, including considerations for I/O voltages and spacing/
separation requirements, in compliance with relevant safety-agency speci-
fications (usually UL/IEC/EN60950).
In particular, for a non-isolated converter's output voltage to meet SELV
(safety extra low voltage) requirements, its input must be SELV compliant.
If the output needs to be ELV (extra low voltage), the input must be ELV.
Input Overvoltage and Reverse-Polarity Protection
LSN D12 SIP Series DC/DC's do not incorporate either input overvoltage
or input reverse-polarity protection. Input voltages in excess of the specified
absolute maximum ratings and input polarity reversals of longer than "instan-
taneous" duration can cause permanent damage to these devices.
Start-Up Time
The VIN to VOUT Start-Up Time is the interval between the time at which a
ramping input voltage crosses the lower limit of the specified input voltage
range (10 Volts) and the fully loaded output voltage enters and remains within
its specified accuracy band. Actual measured times will vary with input source
impedance, external input capacitance, and the slew rate and final value of
the input voltage as it appears to the converter.
The On/Off to VOUT Start-Up Time assumes the converter is turned off via
the On/Off Control with the nominal input voltage already applied to the
converter. The specification defines the interval between the time at which the
converter is turned on and the fully loaded output voltage enters and remains
within its specified accuracy band. See Typical Performance Curves.
Remote Sense
LSN D12 SIP Series DC/DC converters offer an output sense function on
pin 3.
The sense function enables point-of-use regulation for overcoming
moderate IR drops in conductors and/or cabling. Since these are non-isolated
devices whose inputs and outputs usually share the same ground plane,
sense is provided only for the +Output.
The remote sense line is part of the feedback control loop regulating the
DC/DC converter’s output. The sense line carries very little current and
consequently requires a minimal cross-sectional-area conductor. As such, it
is not a low-impedance point and must be treated with care in layout
and cabling. Sense lines should be run adjacent to signals (preferably
ground), and in cable and/or discrete-wiring applications, twisted-pair or
similar techniques should be used. To prevent high frequency voltage differ-
ences between VOUT and Sense, we recommend installation of a 1000pF
capacitor close to the converter.
The sense function is capable of compensating for voltage drops between the
+Output and +Sense pins that do not exceed 10% of VOUT.
[VOUT(+) – Common] – [Sense(+) – Common] ≤ 10%VOUT
Power derating (output current limiting) is based upon maximum output
current and voltage at the converter's output pins. Use of trim and sense
functions can cause the output voltage to increase, thereby increasing output
power beyond the LSN's specified rating. Therefore:
(VOUT at pins) x (IOUT) ≤ rated output power
The internal 10.5Ω resistor between +Sense and +Output (see Figure 1)
serves to protect the sense function by limiting the output current flowing
through the sense line if the main output is disconnected. It also prevents
output voltage runaway if the sense connection is disconnected.
Note: Connect the +Sense pin (pin 3) to +Output (pin 4) at the DC/DC
converter pins, if the sense function is not used for remote regulation.
In particular, the LSN D12's input capacitors are specified for low ESR
and are fully rated to handle the units' input ripple currents. Similarly, the
internal output capacitors are specified for low ESR and full-range frequency
response. As shown in the Performance Curves, removal of the external 22µF
tantalum output caps has minimal effect on output noise.
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.
Output ripple/noise (also referred to as periodic and random deviations
or PARD) may be reduced below specified limits with the installation of
additional external output capacitors. Output capacitors function as true filter
elements and should be selected for bulk capacitance, low ESR, and appro-
priate frequency response. Any scope measurements of PARD should be
made directly at the DC/DC output pins with scope probe ground less than
0.5" in length.
All external capacitors should have appropriate voltage ratings and be located
as close to the converters as possible. Temperature variations for all relevant
parameters should be taken into consideration.
The most effective combination of external I/O capacitors will be a function
of your line voltage and source impedance, as well as your particular load and
layout conditions. Our Applications Engineers can recommend potential solu-
tions and discuss the possibility of our modifying a given device’s internal filter-
ing to meet your specific requirements. Contact our Applications Engineering
Group for additional details.
Input Fusing
Most applications and or safety agencies require the installation of fuses at
the inputs of power conversion components. LSN D12 Series DC/DC con-
verters are not internally fused. Therefore, if input fusing is mandatory, either
a normal-blow or a slow-blow fuse with a value no greater than 20 Amps
should be installed within the ungrounded input path to the converter.
As a rule of thumb however, we recommend to use a normal-blow or slow-
blow fuse with a typical value of about twice the maximum input current,
calculated at low line with the converters minimum efficiency.
LSN-16A D12 Models
N O N - I S O L A T E D , 1 3 - 8 0 W S I P D C / D C C O N V E R T E R S
Output Voltage Trimming
For all models except "T" versions. See "T" Trimming.
Allowable trim ranges for each model in the LSN D12 SIP Series are ±10%.
Trimming is accomplished with either a trimpot or a single fixed resistor. The
trimpot should be connected between +Output and Common with its wiper
connected to the Trim pin as shown in Figure 3 below.
A trimpot can be used to determine the value of a single fixed resistor
which can then be connected, as shown in Figure 4, between the Trim pin
and +Output to trim down the output voltage, or between the Trim pin and
Common to trim up the output voltage. Fixed resistors should have absolute
TCR’s less than 100ppm/°C to ensure stability.
The equations below can be used as starting points for selecting specific trim-
resistor values. Recall, untrimmed devices are guaranteed to be ±1% accurate.
Adjustment beyond the specified ±10% adjustment range is not recommended.
Figure 4. Trim Connections Using Fixed Resistors
Note:
Install either a fixed
trim-up resistor
or a fixed trim-down
resistor depending upon
desired output voltage.
Output Overvoltage Protection
LSN D12 SIP Series DC/DC converters do not incorporate output overvolt-
age protection. In the extremely rare situation in which the device’s feedback
loop is broken, the output voltage may run to excessively high levels (VOUT =
VIN). If it is absolutely imperative that you protect your load against any and
all possible overvoltage situations, voltage limiting circuitry must be provided
external to the power converter.
On/Off Control and Power-up Sequencing
The On/Off Control pin may be used for remote on/off operation. LSN D12 SIP
Series DC/DC's are designed so they are enabled when the control pin is
left open (internal pull-down to Common) and disabled when the control pin is
pulled high (+2.8V to +VIN), as shown in Figure 2 and 2a.
Dynamic control of the on/off function is best accomplished with a mechanical
relay or open-collector/open-drain drive circuit. The drive circuit should be
able to sink appropriate current when activated and withstand appropriate
voltage when deactivated.
Figure 3. Trim Connections Using a Trimpot
Figure 2. Driving the On/Off Control Pin with an External
Open-Collector Drive Circuit
�
5
The on/off control function, however, can be externally inverted so that the
converter will be disabled while the input voltage is ramping up and then
"released" once the input has stabilized.
For a controlled start-up of one or more LSN-D12's, or if several output
voltages need to be powered-up in a given sequence, the On/Off Control pin
can be pulled high (external pull-up resistor, converter disabled) and then
driven low with an external open collector device to enable the converter.
Figure 2a. Inverting On/Off Control Pin with an External CMOS Gate
Output Overcurrent Detection
Overloading the output of a power converter for an extended period of
time will invariably cause internal component temperatures to exceed their
maximum ratings and eventually lead to component failure. High-current-
carrying components such as inductors, FET's and diodes are at the highest
risk. LSN D12 SIP Series DC/DC converters incorporate an output overcur-
rent detection and shutdown function that serves to protect both the power
converter and its load.
If the output current exceeds it maximum rating by typically 60% (24 Amps) or
if the output voltage drops to less than 98% of it original value, the LSN D12's
internal overcurrent-detection circuitry immediately turns off the converter,
which then goes into a "hiccup" mode. While hiccupping, the converter will
continuously attempt to restart itself, go into overcurrent, and then shut down.
Under these conditions, the average output current will be approximately
400mA, and the average input current will be approximately 40mA. Once the
output short is removed, the converter will automatically restart itself.
+INPUT
POWER
COMMON
CONTROLLER
SHUTDOWN
SIGNAL
GROUND
4.12kΩ
15.4kΩ
ON/OFF
CONTROL
+INPUT
POWER
COMMON
CONTROLLER
SHUTDOWN
SIGNAL
GROUND
4.12kΩ
15.4kΩ
ON/OFF
CONTROL
CMOS
LOGIC
LSN-16A D12 Series N O N - I S O L A T E D , 1 3 - 8 0 W S I P D C / D C C O N V E R T E R S
6
Note: Resistor values are in kΩ. Accuracy of adjustment is subject to
tolerances of resistors and factory-adjusted, initial output accuracy.
VO = desired output voltage. VONOM = nominal output voltage.
Trim Equations
�
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"T" Model LSN-T/16-D12
This version of the LSN 16A series offers a special output voltage trimming
feature which is fully compatible with competitive units. The output voltage
may be varied from 0.75 to 5 Volts using a single external trim up resis-
tor connected from the Trim input to Output Common. If no trim resistor is
attached (Trim pin open), the output is 0.7525 Volts.
The trim may also be adjusted using an external reference voltage connected
to the Trim input.
As with other trim adjustments, use a 1% metal film precision resistor with
low temperature coefficient (±100 ppm/°C or less) mounted close to the
converter with short leads. Also be aware that the output accuracy is ±2%
(typical) therefore you may need to vary this resistance slightly to achieve
your desired output setting.
The resistor trim up equation for the LSN-T/16-D12 is as follows:
Where VO is the desired output voltage.
The LSN-T/16-D12 fixed resistance values to set the output values are:
VOUT
(typ.) 0.7525 1.0 1.2 1.5 1.8 2 2.5 3.3 5.0
RTRIM
(kΩ)Open 41.424 22.46 13.05 9.024 7.417 5.009 3.122 1.472
CAUTION: To retain proper regulation, do not exceed the 5 Volt output.
Voltage Trim
The LSN-T/16-D12 may also be trimmed using an external voltage applied
between the Trim input and Output Common. Be aware that the internal
“load” impedance looking into trim pin is approximately 5kΩ. Therefore, you
may have to compensate for this in the source resistance of your external
voltage reference.
The equation for this voltage adjustment is:
VTRIM = 0.7 –(0.0667 x (VO – 0.7525))
The LSN-T/16-D12 fixed trim voltages to set the output voltage are:
VOUT
(typ.) 0.7525 1.0 1.2 1.5 1.8 2 2.5 3.3 5.0
VTRIM Open 0.6835 0.67 0.65 0.63 0.617 0.583 0.53 0.4166
10500
RTRIMUP (Ω) = –1000
VO – 0.7525
LSN-16A D12 Models
N O N - I S O L A T E D , 1 3 - 8 0 W S I P D C / D C C O N V E R T E R S
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 D12 SIP's under known ambient-temperature and air-flow
conditions. Similarly, the curves indicate how much air flow is required to
reliably deliver a specific output current at known temperatures.
The highest temperatures in LSN D12 SIP's occur at their output inductor,
whose heat is generated primarily by I2R losses. The derating curves were
developed 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.
All but the last two DUT's were vertical-mount models, and the direction of air
flow was parallel to the unit in the direction from pin 11 to pin 1.
As you may deduce from the derating curves and observe in the efficiency
curves on the following pages, LSN D12 SIP'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 D12 SIP's are installed in system boards, they are obvi-
ously 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 temperature to ensure it remains below +110°C at all times.
Output Reverse Conduction
Many DC/DC's using synchronous rectification suffer from Output Reverse
Conduction. If those devices have a voltage applied across their output before
a voltage is applied to their input (this typically occurs when another power
supply starts before them in a power-sequenced application), they will either
fail to start or self destruct. In both cases, the cause is the "freewheeling" or
"catch" FET biasing itself on and effectively becoming a short circuit.
LSN D12 SIP DC/DC converters do not suffer from Output Reverse Conduc-
tion. They employ proprietary gate drive circuitry that makes them immune
to applied output voltages.
Voltage Margining
The LSN-T/16-D12 converter can serve as the power source for a production
test environment using voltage margining. This gives the capability to vary
the net output voltage up or down for stress and functional testing of a target
system over the expected power supply voltage range.
Voltage margining requires three external resistors and two switches – the
primary precision trim resistor and two voltage margining resistors. The
switches are typically low on-resistance FET transistors acting as switches.
Devices specifically designed for analog switch applications have effective
closed resistance of a few Ohms and often have a logic gate driving them.
After installing the desired trim resistor, the constant voltage output on the
LSN-T/16-D12 may be adjusted up or down a fixed amount by installing sub-
trim voltage margining resistors as shown on the attached circuit. In effect, an
additional voltage divider is switched in one leg at a time to slightly raise or
lower the output voltage. Typical FET switches are the Maxim MAX4643 and
MAX4544 families.
As with the primary trim resistor, by sure to mount these voltage margining
resistors and switches close to the converter with short leads. Be aware that
the effective output voltage is the result of all error sources including the
trim resistor accuracies and temperature coefficients. Also, the resulting trim
resistor from the equations is usually not a standard precision value therefore
you may have to parallel two resistors.
CAUTION: Switch in only one resistor at a time to invoke voltage margining.
Do not turn on both resistors simultaneously. Also, do not exceed the total
power output of the converter.
Figure 5. LSN-T/16-D12 Voltage Margining
7
LSN-16A D12 Series N O N - I S O L A T E D , 1 3 - 8 0 W S I P D C / D C C O N V E R T E R S
Typical Performance Curves for LSN-16A D12 SIP Series
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Typical Performance Curves for LSN-16A D12 SIP Series
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Typical Performance Curves for LSN-16A D12 SIP Series
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DS-0535B 10/04
11
DATEL makes no representation that the use of its products in the circuits described herein, or the use of other technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein
do not imply the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifications are subject to change without notice. The DATEL logo is a registered DATEL, Inc. trademark.
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