+INPUT
(2)
COMMON
(3)
PWM
CONTROLLER
CURRENT
SENSE
REFERENCE &
ERROR AMP
VCC
ON/OFF
CONTROL
(1)
VOUT
TRIM
(5)
+OUTPUT
(4)
+SENSE
(6)
COMMON
(3)
Single Output
LSM-16A D12 Models
Features
Non-Isolated, 12VIN, 0.75-5VOUT
16 Amp DC/DC’s in SMT Packages
Figure 1. Simplified Schematic
LSM Series D12 SMT's (surface-mount 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. LSM D12 DC/
DC's accept a 12V input (10V to 14V input range) and convert it, with the highest
efficiency in the smallest space, to a 0.75, 1, 1.2, 1.5, 1.8, 2, 2.5, 3.3 or 5 Volt output
fully rated at 16 Amps.
LSM D12's are ideal point-of-use/load power processors. They typically require
no external components. Their surface-mount packages occupy a mere 1.3" x 0.53"
(33.0 x 13.5mm), and are only 0.34 inches (8.6mm) high.
The LSM's best-in-class power density is achieved with a fully synchronous,
fixed-frequency, buck topology that also delivers: high efficiency (95% for 5VOUT
models), low noise (50mVp-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 LSM’s feature output overcurrent detection, continuous
short-circuit protection, over-temperature protection, a remote on/off control pin
(pull low to disable), an output-voltage trim function, and a sense pin. High efficiency
enables the LSM D12's to deliver rated output currents of 16 Amps at ambient tem-
peratures to +65°C with 100 lfm air flow.
If your new system boards call for �multiple 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 LSM D12 SMT's will save you money.
■
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■
■
■
■
■
■
■
■
■
■
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Step-down buck regulators for new
distributed 12V power architectures
12V input (10-14V range)
0.75/1/1.2/1.5/1.8/2/2.5/3.3/5VOUT @16A
Non-isolated, fixed-frequency,
synchronous-rectifier topology
Tape and reel SMT package
±1.25% setpoint accuracy
Efficiencies to 96% @ 16 Amps
Noise as low as 50mVp-p
Stable no-load operation
Remote on/off control
Sense pin and output voltage trim
No derating to +65°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
LSM-16A D12 Series N O N - I S O L A T E D , 1 3 - 8 0 W S M T D C / D C C O N V E R T E R S
2
Pin Function P63
1 On/Off Control
2 +Input
3 Common
4 +Output
5 VOUT Trim
6 +Sense
I/O Connections
LSM-0.75/16-D12 0.75 16 50 75 ±0.1% ±0.375% 12 10-14 35/1.26 83% 85% 86% C45, P63
LSM-1/16-D12 1 16 50 75 ±0.1% ±0.25% 12 10-14 35/1.57 83% 85% 86% C45, P63
LSM-1.2/16-D12 1.2 16 50 75 ±0.1% ±0.25% 12 10-14 40/1.84 85% 87% 88% C45, P63
LSM-1.5/16-D12 1.5 16 50 75 ±0.1% ±0.25% 12 10-14 50/2.26 86.5% 88.5% 89.5% C45, P63
LSM-1.8/16-D12 1.8 16 50 75 ±0.1% ±0.25% 12 10-14 55/2.67 88% 90% 91% C45, P63
LSM-2/16-D12 2 16 50 75 ±0.1% ±0.25% 12 10-14 55/2.93 89% 91% 91.5% C45, P63
LSM-2.5/16-D12 2.5 16 50 75 ±0.1% ±0.25% 12 10-14 60/3.62 90% 92% 91.5% C45, P63
LSM-3.3/16-D12 3.3 16 50 75 ±0.1% ±0.25% 12 10-14 70/4.68 92% 94% 94.5% C45, P63
LSM-5/16-D12 5 16 75 100 ±0.1% ±0.25% 12 10-14 85/7.06 92.5% 94.5% 95.5% C45, P63
LSM-T/16-D12 0.75-5 16 50 75 ±0.1% ±0.25% 12 10-14 85/7.02 93% 95% 95.5% C45, P63
➀ Typical at TA = +25°C under nominal line voltage and full-load conditions, 200 lfm air flow for
extended operation, unless otherwise 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.
MECHANICAL SPECIFICATIONS
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.
PART NUMBER STRUCTURE
Performance Specifications and Ordering Guide ➀
Package
VOUT IOUT VIN Nom. Range IIN ➃ (Case,
Model (Volts) (Amps) Typ. Max. Line Load (Volts) (Volts) (mA/A) Min. Typ. Typ. Pinout)
Output Input
R/N (mVp-p) ➁ Regulation (Max.) ➂
Case C45
Maximum Rated Output
Current in Amps
Non-Isolated SMT
Output
Configuration:
L = Unipolar
Low Voltage
Nominal Output Voltage:
0.75, 1, 1.2, 1.5, 1.8, 2, 2.5, 3.3
or 5 Volts
Input Voltage Range:
D12 = 10 to 14 Volts
(12V nominal)
L SM 16-/D12-1.8
BOTTOM VIEW
1.36
(34.54)
0.375
(9.53)
0.112 TYP.
(2.84)
0.052
(1.32)
LSM WITH REMOVEABLE HEAT SHIELD
FOR HIGH TEMPERATURE SOLDER
CAUTION
PRESS TO REMOVE
THE HEAT SHIELD
AFTER THE SOLDER
PROCESS
0.60
(15.24)
0.049
(1.24)
0.310
(7.87)
0.010
(0.254)
0.55
(13.97)
0.052
(1.32)
0.062
(1.57)
0.047
(1.19)
0.570 (14.48)
3 EQ. SP. @
0.190 (4.83)
2
3 4 5 6
1
NOTCH IN SHELL
INDICATES
PIN ONE.
Refer to the last page for
Tape and Reel information.
Efficiency ( Full load)
VIN = nom. VIN = min.
DIMENSIONS ARE IN INCHES (MM)
Note: Not all model number combinations
are available. Contact DATEL.
LSM-16A D12 Models
N O N - I S O L A T E D , 1 3 - 8 0 W S M T 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
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 See Technical Notes and Performance Curves for details.
➂ The On/Off Control (pin 1) is designed to be driven with open-collector logic or the appli-
cation of appropriate voltages (referenced to Common, pin 3). Applying a voltage to On/Off
Control when no input voltage is applied to the converter may cause permanent damage.
➃ Output noise may be further reduced with the installation of additional external output
filtering. See I/O Filtering and Noise Reduction.
➄ MTBF’s are calculated using Telcordia SR-332(Bellcore), ground fixed, TA = +25°C, full
power, natural convection, +67°C pcb temperature.
➅ Input Ripple Current is tested/specified over a 5Hz-20MHz bandwidth with an external 2 x
100µF input capacitor and a simulated source impedance of 1000µF and 1µH. See I/O
Filtering, Input Ripple Current and Output Noise for details.
TECHNICAL NOTES
Input Voltage:
Continuous or transient 15 Volts
On/Off Control (Pin 1) +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 See Reflow 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
I/O Filtering and Noise Reduction
All models in the LSM 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 LSM 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.
In particular, the LSM 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.
Input
Input Voltage Range 10-14 Volts (12V nominal)
Startup Voltage 8.5-9.2 Volts (model dependent)
Input Current:
Normal Operating Conditions See Ordering Guide
Inrush Transient 0.08A2 sec
Standby/Off Mode 1.5mA
Output Short-Circuit Condition ➁ 12-40mA average (model dependent)
Input Reflected Ripple Current ➁ ➅ 20-50mAp-p, model dependent
Input Filter Type Capacitive
Overvoltage Protection None
Reverse-Polarity Protection None
Undervoltage Shutdown 7.5-8 Volts (model dependent)
On/Off Control ➁ ➂ On = open (internal pull-up to +VIN)
Off = 0 to +0.4V (1mA max.)
Output
VOUT Accuracy (50% load) ±1.25% maximum
Minimum Loading ➀ No load
Maximum Capacitive Load 1000µF (low ESR, OSCON)
VOUT Trim Range ±10%
Ripple/Noise (20MHz BW) ➀ ➁ ➃ See Ordering Guide
Total Accuracy 3% over line/load/temperature
Efficiency See Ordering Guide
Overcurrent Detection and Short-Circuit Protection: ➁
Current-Limiting Detection Point 21-31 Amps (model dependent)
Short-Circuit Detection Point 98% of VOUT set
SC Protection Technique Hiccup with auto recovery
Short-Circuit Current 125-420mA average (model dependent)
Dynamic Characteristics
Transient Response (50% load step) 30-135µsec to ±2% of final value
(model dependent)
Start-Up Time: ➁
VIN to VOUT and On/Off to VOUT 60msec for VOUT = 1V and 0.75V
40msec for VOUT = 1.2V to 5V
Switching Frequency 260kHz ±10%
Environmental
Calculated MTBF ➄
LSM-1.2/16-D12 9,160,138 hours
LSM-1.5/16-D12 8,674,318 hours
LSM-1.8/16-D12 8,334,117 hours
LSM-2.5/16-D12 8,534,580 hours
LSM-3.3/16-D12 7,817,255 hours
LSM-5/16-D12 7,756,061 hours
Operating Temperature: (Ambient) ➁
Without Derating (Natural convection) –40 to +33/64°C (model dependent)
With Derating See Derating Curves
Thermal Shutdown +115°C (110 to 125°C)
Physical
Dimensions 1.3" x 0.53" x 0.34" (33.03 x 13.46 x 8.64)
Pin Dimensions/Material 0.112" x 0.062" (2.84 x 1.57mm) rectangular
copper with gold plate over nickel underplate
Weight 0.28 ounces (7.8g)
Flamability Rating UL94V-0
LSM-16A D12 Series N O N - I S O L A T E D , 1 3 - 8 0 W S M T D C / D C C O N V E R T E R S
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. The LSM D12 Series are not
internally fused. Therefore, if input fusing is mandatory, either a normal-blow
or a fast-blow fuse with a value no greater than twice the maximum input cur-
rent 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.
4
Input Overvoltage and Reverse-Polarity Protection
LSM D12 SMT 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.
Figure 3. Measuring Output Ripple/Noise (PARD)
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.
C1
C1 = NA
C2 = 22µF TANTALUM
LOAD 2-3 INCHES (51-76mm) FROM MODULE
C2 RLOAD
6
4
COPPER STRIP
3
COPPER STRIP
SCOPE
+OUTPUT
COMMON
+SENSE
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.
Remote Sense
LSM D12 SMT Series DC/DC converters offer an output sense function on
pin 6.
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 tech-
niques should be used. To prevent high frequency voltage differences 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 cur-
rent and voltage at the converter's output pins. Use of trim and sense func-
tions can cause the output voltage to increase, thereby increasing output
power beyond the LSM's specified rating. Therefore:
(VOUT at pins) x (IOUT) ≤ rated output power
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Figure 2. Measuring Input Ripple Current
Safety Considerations
LSM D12 SMT's are non-isolated DC/DC converters. In general, all DC/DC's
must be installed, including considerations for I/O voltages and spacing/sepa-
ration 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.
LSM-16A D12 Models
N O N - I S O L A T E D , 1 3 - 8 0 W S M T D C / D C C O N V E R T E R S
Output Overcurrent Detection
Overloading the power converter's output for an extended 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. LSM D12 SMT Series
DC/DC converters incorporate an output overcurrent 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 70% (27 Amps)
or if the output voltage drops to less than 98% of it original value, the LSM
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.
Output Voltage Trimming
Allowable trim ranges for each model in the LSM D12 SMT 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 6 below.
A trimpot can be used to determine the value of a single fixed resistor
which can then be connected, as shown in Figure 7, 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 starting points for selecting specific trim-resistor
values. Recall, untrimmed devices are guaranteed to be ±1.25% accurate.
Adjustment beyond the specified ±10% adjustment range is not recommended.
When using trim in combination with Remote Sense, the maximum rated power
must not be exceeded (see Remote Sense).
On/Off Control
The On/Off Control pin may be used for remote on/off operation. LSM D12
Series DC/DC converters are designed so that they are enabled when the
control pin is left open (open collector) and disabled when the control pin is
pulled low (to less than +0.4V relative to Common). As shown in Figure 4, all
models have an internal pull-up current source to VIN (+Input).
Dynamic control of the on/off function is best accomplished with a mechanical
relay or open-collector/open-drain drive circuit (optically isolated if appropri-
ate). The drive circuit should be able to sink appropriate current when
activated and withstand appropriate voltage when deactivated.
5
Applying an external voltage to the On/Off Control pin when no input power is
applied to the converter can cause permanent damage to the converter. The
on/off control function, however, is designed such that the converter can be
disabled (control pin pulled low) while input voltage is ramping up and then
"released" once the input has stabilized (see also power-up sequencing).
Figure 5. Driving The External Power-Up Open Collector
Power-up sequencing
If a controlled start-up of one or more LSM D12 Series DC/DC converters
is required, or if several output voltages need to be powered-up in a given
sequence, the On/Off control pin can be driven with an external open collec-
tor device as per Figure 5.
Leaving the input of the on/off circuit closed during power-up will have the
output of the DC/DC converter disabled. When the input to the external open
collector is pulled high, the DC/DC converter's output will be enabled.
Output Overvoltage Protection
LSM D12 SMT 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.
Figure 4. On/Off Control Using An External Open Collector Driver
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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: If the sense function is not used for remote regulation, +Sense
(pin 6) must be tied to +Output (pin 4) at the DC/DC converter pins.
LSM-16A D12 Series N O N - I S O L A T E D , 1 3 - 8 0 W S M T D C / D C C O N V E R T E R S
6
Figure 7. Trim Connections Using Fixed Resistors
Figure 6. Trim Connections Using a Trimpot
�
Trim Equations
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.
�
�
Note: Install either a fixed trim-up resistor
or a fixed trim-down resistor depending upon
desired output voltage.
“T” Model LSM-T/16-D12
This version of the LSM 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 LSM-T/16-D12 is as follows:
10500
RTUP (Ω) = ___________ –1000
VO – 0.7525
Where VO is the desired output voltage.
The LSM-T/16-D12 fixed resistance values to set the output values are:
VO 0.7525V 1.0V 1.2V 1.5V 1.8V 2.5V 3.3V 5.0V
RT (kΩ) Open 41.424 22.46 13.05 9.024 5.009 3.122 1.472
CAUTION: To retain proper regulation, do not exceed the 5 Volt output.
Voltage Trim
The LSM-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 LSM-T/16-D12 fixed trim voltages to set the output voltage are:
VO 0.7525V 1.0V 1.2V 1.5V 1.8V 2.5V 3.3V 5.0V
VT (V) Open 0.6835 0.670 0.650 0.630 0.583 0.530 0.4166
LSM-16A D12 Models
N O N - I S O L A T E D , 1 3 - 8 0 W S M T D C / D C C O N V E R T E R S
7
The highest temperatures in LSM D12 SMT'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.
As you may deduce from the derating curves and observe in the efficiency
curves on the following pages, LSM D12 SMT'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 LSM D12 SMT'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.
LSM D12 SMT DC/DC converters do not suffer from Output Reverse
Conduction. They employ proprietary gate drive circuitry that makes them
immune to applied output voltages.
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 LSM D12 SMT'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.
LSM-16A D12 Series N O N - I S O L A T E D , 1 3 - 8 0 W S M T D C / D C C O N V E R T E R S
8
Typical Performance Curves for LSM D12 SMT Series
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LSM-16A D12 Models
N O N - I S O L A T E D , 1 3 - 8 0 W S M T D C / D C C O N V E R T E R S
Typical Performance Curves for LSM D12 SMT Series
9
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LSM-16A D12 Series N O N - I S O L A T E D , 1 3 - 8 0 W S M T D C / D C C O N V E R T E R S
Typical Performance Curves for LSM D12 SMT Series
10
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LSM-16A D12 Models
N O N - I S O L A T E D , 1 3 - 8 0 W S M T D C / D C C O N V E R T E R S
11
Tape & Reel Surface Mount Package
DATEL's LSM series DC/DC converters are the only higher-current (16A)
SMT DC/DC's that can be automatically "pick-and-placed" using standard
vacuum-pickup equipment (nozzle size and style, vacuum pressure and
placement speed may need to be optimized for automated pick and place)
and subsequently reflowed using high-temperature, lead-free solder.
Virtually all SMT DC/DC's today are unprotected "open-frame" devices
assembled by their vendors with high-temperature solder (usually
Sn96.5/Ag3.5 with a melting point +221°C) so that you may attach them
to your board using low-temperature solder (usually Sn63/Pb37 with a melt-
ing point of +183°C). Conceptually straightforward, this "stepped" solder
approach has its limitations, and it is clearly out of step with an industry
trending toward the broad use of lead-free solders. Are you to experiment
and develop reflow profiles from other vendors that ensure the components
on those DC/DC never exceed 215-216°C? If those components get too hot,
"double-reflow" could compromise the reliability of their solder joints. Virtually
all these devices demand you "cool down" the Sn63 profile you are likely
using today.
Figure 6. Reflow Solder Profile
DATEL is not exempted from the Laws of Physics, and we do not have magic
solders no one else has. Nevertheless, we have a simple and practical,
straightforward approach that works. We assemble our LSM SMT DC/DC's
using a high-temperature (+216°C), lead-free alloy (Sn96.2%, Ag2.5%,
Cu0.8%, Sb0.5%). The LSM design ensures co-planarity to within 0.004
inches (100µm) of the unit's tin-plated (150 micro-inches) copper leads. See
Mechanical Data for additional information.
The disposable heat shield (patent pending), which has a cutaway exposing
the package leads, provides thermal insulation to internal components during
reflow and its smooth surface ideally doubles as the vacuum pick-up location
also. The insulation properties of the heat shield are so effective that tem-
perature differentials as high as 50°C develop inside-to-outside the shield.
Oven temperature profiles with peaks of 250-260°C and dwell times exceed-
ing 2 minutes above 221°C (the melting point of Sn96.5/Ag3.5) are easily
achieved.
HEAT SHIELD OUTSIDE TEMPERATURE
Sn96.5/Ag3.5 Melting Point
Sn63/Pb37 Melting Point
250
200
150
100
50
0 50 100 150 200 250 300 350 400
221
183
PCB TEMPERATURE INSIDE THE HEAT SHIELD
Temperature (˚C)
Time
(
Seconds
)
12
LSM-16A D12 Series N O N - I S O L A T E D , 1 3 - 8 0 W S M T D C / D C C O N V E R T E R S
DS-0544 3/05
0.51(13.0)
7.38 (187.5)
13.0 (330.2)
2.44
(62.0)
Figure 8. Reel Dimensions
DATEL's new-generation LSM SMT DC/DC converters are shipped in quantities of 150 modules per tape and reel.
Figure 7. Tape Dimensions
CAUTION
PRESS TO REMOVE
THE HEAT SHIELD
AFTER THE SOLDER
PROCESS.
NOTCH IN SHELL
INDICATES
PIN ONE.
0.158
(4) CENTERED
PICK UP
LOCATION
2.205
(56)
2.063
(52.4)
FEED
DIRECTION
1.370
(34.8)
1.102
(28)
0.605
(15.36)
TAPE
0.590
(14.97)
DIMENSIONS
IN INCHES (mm)
111
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.
DATEL (UK) LTD. Tadley, England Tel: (01256)-880444
Internet: www.datel-europe.com E-mail: datel.ltd@datel.com
DATEL S.A.R.L. Montigny Le Bretonneux, France Tel: 01-34-60-01-01
Internet: www.datel-europe.com E-mail: datel.sarl@datel.com
DATEL GmbH München, Germany Tel: 89-544334-0
Internet: www.datel-europe.com E-mail: datel.gmbh@datel.com
DATEL KK Tokyo, Japan Tel: 3-3779-1031, Osaka Tel: 6-6354-2025
Internet: www.datel.co.jp Email: salestko@datel.co.jp, salesosa@datel.co.jp
DATEL China Shanghai, China Tel: 011-86-51317131
E-mail: davidx@datel.com
DATEL, Inc. 11 Cabot Boulevard, Mansfield, MA 02048-1151
Tel: (508) 339-3000 (800) 233-2765 Fax: (508) 339-6356
www.datel.com Email: sales@datel.com
www.cdpowerelectronics.com
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