PRELIMINARY
®
®
A SUBSIDIARY OF C&D TECHNOLOGIES
LSM-16A W3 Models
Single Output
Non-Isolated, 3-5.5V
IN
, 0.75-3.3V
OUT
16 Amp DC/DC’s in SMT Packages
Features
■
Step-down, wide input buck regulators
for distributed 3-5V power architectures
3V to 5V wide-input range
0.75/1/1.2/1.5/1.8/2/2.5/3.3V
OUT
@16A
Non-isolated, fixed-frequency,
synchronous-rectifier topology
Tape and reel SMT package
±1% setpoint accuracy
Efficiencies to 95% @ 16 Amps
Noise as low as 30mVp-p
Stable no-load operation
Remote on/off control
Sense pin and output voltage trim
No derating to +65°C with no fan
UL/IEC/EN60950 certification pending
EMC compliant
■
■
■
■
■
■
■
■
■
■
■
■
■
LSM Series W3 SMT's (surface-mount packages) are ideal building blocks for
emerging, on-board power-distribution schemes in which isolated 3 to 5.5V buses
deliver power to any number of non-isolated, step-down buck regulators. LSM W3
DC/DC's accept 3 to 5.5 Volts and convert it, with the highest efficiency in the small-
est space, to a 0.75, 1, 1.2, 1.5, 1.8, 2, 2.5, or 3.3 Volt output fully rated at 16 Amps.
LSM W3'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 (97%, 3.3V
OUT,
8A),
low noise (30mVp-p typ.), tight line/load regulation (±0.1%/±0.25% max.), quick step
response (30µsec), 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 W3's to deliver rated output currents of 16 Amps at ambient tem-
peratures to +65°C with natural convection.
If your new system boards call for multiple supply voltages, check out the eco-
nomics of on-board 3-5.5V distributed power. If you don't need to pay for multiple
isolation barriers, DATEL's non-isolated LSM W3 SMT's will save you money.
+INPUT
(2)
+OUTPUT
(4)
+SENSE
(6)
COMMON
(3)
CURRENT
SENSE
V
CC
ON/OFF
CONTROL
(1)
COMMON
(3)
PWM
CONTROLLER
REFERENCE &
ERROR AMP
V
OUT
TRIM
(5)
Figure 1. Simplified Schematic
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
LSM-16A W3 Series
N O N - I S O L AT E D , W I D E I N P U T S M T D C / D C C O N V E R T E R S
Performance Specifications and Ordering Guide
➀
Output
Model
LSM-0.75/16-W3
LSM-1/16-W3
LSM-1.2/16-W3
LSM-1.5/16-W3
LSM-1.8/16-W3
LSM-2/16-W3
LSM-2.5/16-W3
LSM-3.3/16-W3
LSM-T/16-W3
➅
V
OUT
(Volts)
0.75
1
1.2
1.5
1.8
2
2.5
3.3
0.75-3.3
I
OUT
(Amps)
16
16
16
16
16
16
16
16
16
R/N (mVp-p)
➁
Typ.
30
30
30
30
30
30
30
30
30
Max.
50
50
50
50
50
50
50
50
50
Regulation (Max.)
➂
Line
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
Load
±0.25%
±0.25%
±0.25%
±0.25%
±0.25%
±0.25%
±0.25%
±0.25%
±0.25%
V
IN
Nom
(Volts)
5
5
5
5
5
5
5
5
5
Input
Range
(Volts)
3-5.5
3-5.5
3-5.5
3-5.5
3-5.5
3-5.5
3-5.5
I
IN
➃
(mA/A)
70/2.98
70/3.72
70/4.36
70/5.33
70/6.30
70/6.92
70/8.56
50/11.12
50/11.12
Efficiency (Full Load)
V
IN
= nom.
Min.
80%
84%
86%
88%
89.5%
90.5%
91.5%
93%
93%
Typ.
82%
86%
88%
90%
91.5%
92.5%
93.5%
95%
95%
V
IN
= min.
Typ.
81.5%
86.5%
88.5%
90.5%
92%
92.5%
94%
95%
95.5%
Package
(Case
Pinout)
C45, P63
C45, P63
C45, P63
C45, P63
C45, P63
C45, P63
C45, P63
C45, P63
C45, P63
➄
➄
➀
Typical at T
A
= +25°C under nominal line voltage and full-load conditions, unless noted. All
models are tested/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
V
IN
= 4.5 Volts minimum for V
OUT
= 3.3 Volts.
➄
LSM-T/16-W3 specs are given with V
OUT
= 3.3 Volts, unless noted.
P A R T
N U M B E R
S T R U C T U R E
M E C H A N I C A L
S P E C I F I C A T I O N S
½½½½
½½½½½½½
L SM
-
1.8
/
16
-
W3
Output
Configuration:
L
= Unipolar
Low Voltage
Non-Isolated SMT
Nominal Output Voltage:
0.75, 1, 1.2, 1.5, 1.8, 2, 2.5, 3.3
or 0.75-3.3 (T) Volts
Input Voltage Range:
W3
= 3 to 5.5 Volts
(5V nominal)
Maximum Rated Output
Current in Amps
½½½½
½½½½½½
½½½½½½½½½½½½½½½½
½½½½½½½½½½½½½½
½½½½½
½½½½½½
½½½½½½½½½½½½½
½½½½½½½½½½½
½½½½½½½½½½½½
½½½½½
½½½½½½
1.36
(34.54)
½½½½½
½½½½½½
½½½½
½
½
½
½
½
½
Case C45
½½½½
½½½½½½
½½½½
½½½½
½½½½½½½
½½½½½½½
½½½½½½½½½½½
0.55
(13.97)
½½½½½
½½½½½½
½½½½
½½½½½
½½½½½½
½½½½½
½½½½½½
½½½½½
½½½½½½½
½½½½½½½½½½½½½
½½½½½½½½½½½
½½½½½½½½½½½½
0.010
(0.254)
0.570 (14.48)
3 EQ. SP. @
0.190 (4.83)
0.60
(15.24)
½½½½½
½½½½½½
½½½½½
½½½½½½
0.310
(7.87)
0.375
(9.53)
0.052
(1.32)
Refer to the last page for
Tape and Reel information.
½½½½½
½½½½½½½
½
½
½
½
½
½
½½½½½
½½½½½½½
3
4
5
6
0.062
(1.57)
½½½½½½½½½½½½½½½½½½½½½½
2
1
½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½
0.112 TYP.
(2.84)
0.049
(1.24)
0.047
(1.19)
BOTTOM VIEW
0.052
(1.32)
LSM WITH REMOVEABLE HEAT SHIELD
FOR HIGH TEMPERATURE SOLDER
DIMENSIONS IN INCHES (mm
)
CAUTION
PRESS TO REMOVE
THE HEAT SHIELD
AFTER THE SOLDER
PROCESS
NOTCH IN SHELL
INDICATES
PIN ONE.
Pin
1
2
3
4
5
6
I/O Connections
Function P63
On/Off Control
+Input
Common
+Output
V
OUT
Trim
+Sense
2
N O N - I S O L AT E D , W I D E I N P U T S M T D C / D C C O N V E R T E R S
LSM-16A W3 Models
Performance/Functional Specifications
Typical @ T
A
= +25°C under nominal line voltage, 200 lfm air flow, and full-load conditions
unless noted.
➀
Input Voltage Range
Input Current:
Normal Operating Conditions
Inrush Transient
Standby/Off Mode
Output Short-Circuit Condition
➁
Input Reflected Ripple Current
➁ ➅
Input Filter Type
Overvoltage Protection
Reverse-Polarity Protection
Undervoltage Shutdown
On/Off Control
➁ ➂
Input
3-5.5 Volts (5V nominal)
➇
See Ordering Guide
0.02A
2
sec
8mA
60-110mA average (model dependent)
10-70mAp-p, model dependent
Capacitive
None
None
None
On = open to +V
IN
(internal pull-up to +V
IN
)
Off = 0 to +0.4V (1mA)
➀
All models are tested/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, T
A
= +25°C, full
power, natural convection, +67°C pcb temperature.
➅
Input Ripple Current is tested/specified over a 5-20MHz 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.
➆
LSM-0.75/16-W3 can not be trimmed down.
➇
Input voltage must be 4.5V minimum for 3.3V output.
Absolute Maximum Ratings
Input Voltage:
Continuous or transient
On/Off Control
(Pin 1)
Input Reverse-Polarity Protection
Output Overvoltage Protection
Output Current
6 Volts (0.75, 1, 1.2, 1.5, 1.8, 2, 2.5 V
OUT)
7 Volts (3.3V
OUT
and "T" models)
+V
IN
None
None
Current limited. Devices can
withstand sustained output short
circuits without damage.
–40 to +125°C
See Reflow Solder Profile
V
OUT
Accuracy
(50% load)
Temperature Coefficient
Minimum Loading
➀
Maximum Capacitive Load
Output
±1.5%
±0.02%/°C
No load
5000µF (electrolytic),
2000µF (0.02Ω ESR, OSCON)
V
OUT
Trim Range
±10%
➆
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
24-28 Amps (model dependent)
Short-Circuit Detection Point
98% of V
OUT
set
SC Protection Technique
Hiccup with auto recovery
Short-Circuit Current
600mA average
Storage Temperature
Lead Temperature
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.
Dynamic Characteristics
Transient Response
(50% load step) 30-70µsec to ±2% of final value
(model dependent)
Start-Up Time:
➁
7msec
V
IN
to V
OUT
and On/Off to V
OUT
Switching Frequency
300 ±50kHz
T E C H N I C A L
N O T E S
I/O Filtering and Noise Reduction
All models in the LSM W3 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'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'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.
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.
Environmental
Calculated MTBF
➄
TBD
Operating Temperature:
(Ambient)
➁
Without Derating (Natural convection) –40 to +63/71°C (model dependent,
see Derating Curves)
With Derating
See Derating Curves
Maximum PC Board Temperature
Thermal Shutdown
EMI
Conducted or radiated,
FCC Part 15, EN55022
Safety
Dimensions
Pin Dimensions/Material
Weight
Flamability Rating
+100°C
+115°C (110 to 125°C)
Class B
UL/IEC/EN60950, CSA-C22.2 No. 234
Physical
1.3" x 0.53" x 0.34" (33.03 x 13.46 x 8.64)
0.112" x 0.062" (2.84 x 1.57mm) rectangular
copper with gold plate over nickel underplate
0.28 ounces (7.8g)
UL94V-0
3
LSM-16A W3 Series
N O N - I S O L AT E D , W I D E I N P U T S M T D C / D C C O N V E R T E R S
½½½
½½½½½½½½½½½½
Safety Considerations
½½½½½½½
½½½½½
½
½½½
½
½½½½½½
½
½
½½
½
½
½½½
½
½½
½
LSM W3 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.
Input Overvoltage and Reverse-Polarity Protection
LSM W3 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 V
IN
to V
OUT
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 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 V
OUT
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
LSM W3 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
V
OUT
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 V
OUT
.
[V
OUT
(+) – Common] – [Sense(+) – Common]
≤
10%V
OUT
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:
(V
OUT
at pins) x (I
OUT
)
≤
rated output power
½½½½½½
½
½½
½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½
½
½½½
½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½
½
½½½
½½½½½½
Figure 2. Measuring Input Ripple Current
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.
+SENSE
+OUTPUT
6
4
COPPER STRIP
C1
C2
SCOPE
R
LOAD
COMMON
3
COPPER STRIP
C1 = NA
C2 = 22µF TANTALUM
LOAD 2-3 INCHES (51-76mm) FROM MODULE
Figure 3. Measuring Output Ripple/Noise (PARD)
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. The LSM W3 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 converter's minimum efficiency.
4
N O N - I S O L AT E D , W I D E I N P U T S M T D C / D C C O N V E R T E R S
LSM-16A W3 Models
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.
On/Off Control
The On/Off Control pin may be used for remote on/off operation. LSM W3
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 V
IN
(+Input).
Dynamic control of the on/off function is best accomplished with a mechani-
cal relay or open-collector/open-drain drive circuit (optically isolated if appro-
priate). The drive circuit should be able to sink appropriate current when
activated and withstand appropriate voltage when deactivated.
½½½½½½
½½½½½½½½
½½½½½
½½½½½½½½½
½½½½½
½½½½½½
½½½½
½½
½½½½½½
½½½½½½½
½½½½½½
½½½½½½
½½½½½½
½½½½½½½½
½½½½½½½½½½
Figure 5. Inverting On/Off Control With An External CMOS Gate
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 W3 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 50% (24 Amps)
or if the output voltage drops to less than 98% of it original value, the LSM
W3'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 W3 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% 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).
½½½
½½½½½
½½½½½½
½½½½½½½½½½
½½½½½½½½
½½½½½½½
½½½½½½
½½½½½½½
½½½½½½
½½½½½½
½½½½½½
½½
½½½½½½½½
½½½½½½½½½½
Figure 4. On/Off Control Using An External Open Collector Driver
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).
Power-up sequencing
If a controlled start-up of one or more LSM W3 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 4.
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 W3 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 (V
OUT
=
V
IN
). 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.
5
Making friends through disassembly
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