LEN-D12 Models
Non-Isolated, 28A Eighth Brick
DC/DC Converters
NOT RECOMMENDED
FOR NEW DESIGNS
FEATURES
Eighth brick, through hole or SMT
2-phase buck regulators for new
distributed 12V power architectures
12V input (10.2-13.8V range)
0.8-2.5V
OUT
, 3.3V
OUT
@ 28A, 5V
OUT
@ 25A
Non-isolated, fixed-frequency
Synchronous-rectifier topology
Efficiencies to 95% @ 25 Amps
Noise as low as 25mVp-p
Stable no-load operation
On/Off control, trim & sense functions
Input Over/Undervoltage lockout
Thermal shutdown
Designed to meet UL/EN/IEC60950-1
EMC compliant
Typical Units
Non Isolated, 12V
IN
, 0.8-5V
OUT
28 Amp DC/DC Converters
PRODUCT OVERVIEW
The LEN D12 Series of non-isolated eighth
bricks are ideal building blocks for emerg-
ing, on-board power-distribution schemes
in which isolated 12V buses deliver power
to any number of non-isolated, step-down
buck regulators. LEN D12 DC/DCs accept a
12V input (10.2V to 13.8V input range) and
convert it, with the highest efficiency in the
smallest space, to a 0.8, 1, 1.2, 1.5, 1.8, 2,
2.5, or 3.3 Volt output fully rated at 28 Amps,
or 5 Volt output at 25 Amps.
LEN D12s are ideal POLPP's (point-of-use/
load power processors) and they typically re-
quire no external components. They occupy the
standard eighth-brick board space (0.9" x 2.3")
and come in either through-hole packages or
surface-mount packages with a profile of only
0.46" (0.5" including optional heat sink).
The LEN's best-in-class power density is
achieved with a fully synchronous,fixed-
frequency, 2-phase buck topology that deliv-
ers extremely high efficiency (95% for 5V
OUT
models), low noise (25mVp-p typ.), tight
line/load regulation (±0.25% max.), quick
step response (150μsec), stable no-load
operation, and no output reverse conduction.
The fully functional LEN's feature input
over/undervoltage lockout, output overvolt-
age and overcurrent detection, continuous
short-circuit protection, overtemperature
protection, an output-voltage trim function,
a remote on/off control pin, and a sense pin.
High efficiency enables the LEN D12s to
deliver rated output currents of 25 Amps at
ambient temperatures to +65°C with 200 lfm
air flow without heat sink.
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,
MPS’s non-isolated ¼ and
1
∕
8
brick’s will save
you money.
For full details go to
www.murata-ps.com/rohs
Typical topology is shown
+OUTPUT
(7,9)
+INPUT
(5)
+SENSE
(10)
COMMON
(1)
CURRENT
SENSE
COMMON
(6, 8)
V
CC
ON/OFF
CONTROL
(4)
2-PHASE
PWM
CONTROLLER
REFERENCE &
ERROR AMP
Only one phase of two shown.
V
OUT
TRIM
(2)
Figure 1. Simplified Schematic
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MDC_LEN D12 Models.B01 Page 1 of 10
LEN-D12 Models
Non-Isolated, 28A Eighth Brick
DC/DC Converters
Performance Specifications and Ordering Guide
ORDERING GUIDE
Output
V
OUT
I
OUT
R/N (mVp-p)
(Volts) (Amps) Typ.
Max.
0.8
28
30
50
1
28
30
50
1.2
28
30
50
1.5
28
20
50
1.8
28
20
50
2
28
20
50
2.5
28
20
50
3.3
28
30
50
5
25
30
50
Regulation (Max.)
Line
Load
±0.25%
±0.25%
±0.25%
±0.25%
±0.25%
±0.25%
±0.25%
±0.25%
±0.2%
±0.25%
±0.25%
±0.25%
±0.25%
±0.25%
±0.25%
±0.25%
±0.25%
±0.25%
V
IN
Nom.
(Volts)
12
12
12
12
12
12
12
12
12
Input
Range
(Volts)
10.2-13.8
10.2-13.8
10.2-13.8
10.2-13.8
10.2-13.8
10.2-13.8
10.2-13.8
10.2-13.8
10.2-13.8
I
IN
(mA/A)
80/2.3
80/2.8
83/3.3
89/4
92/4.7
100/5.2
130/6.4
130/7.4
130/11
Efficiency
Full Load
½ Load
Min.
Typ.
Typ.
79%
80%
84.5%
80%
82.5%
86%
83%
86.5%
88%
85%
88%
90%
89%
90%
91%
88%
90%
91.5%
89%
91%
93%
91%
93%
94%
92%
95%
95.5%
Package
(Case, Pinout)
C43,C44, P62
C43,C44, P62
C43,C44, P62
C43,C44, P62
C43,C44, P62
C43,C44, P62
C43,C44, P62
C43,C44, P62
C43,C44, P62
Models
LEN-0.8/28-D12
LEN-1/28-D12
LEN-1.2/28-D12
LEN-1.5/28-D12
LEN-1.8/28-D12
LEN-2/28-D12
LEN-2.5/28-D12
LEN-3.3/28-D12
LEN-5/25-D12
Typical at T
A
= +25°C under nominal line voltage and full-load conditions, unless otherwise noted.
All models are tested and specified with external 33μF capacitor installed across their input and
output pins.
Ripple/Noise (R/N) is tested/specified over a 20MHz bandwidth.
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.
Nominal line voltage, no-load/full-load conditions.
The operating input voltage is 10.2V to 13.8V. However, 10.8V
IN
is required for the DC/DC to
properly start up under all line, load and temperature conditions. The 10.8V potential must be
maintained across the inputs until the output is up and regulating. After the output is regulating, the
operating input range is 10.2V to 13.8V.
There are incomplete model numbers. Please refer to the Part Number Structure when ordering.
PART NUMBER STRUCTURE
MECHANICAL SPECIFICATIONS
0.50 (12.7)
W/ HEATSINK
0.46 (11.68)
WO/ HEATSINK
Case C43
2.30 (58.42)
2.23 (56.64)
L EN
-
1.8
/
28
-
D12 M H
-
C
Output
Configuration:
L
= Unipolar
Low Voltage
Non-Isolated Eighth Brick
Nominal Output Voltage:
0.8, 1, 1.2, 1.5, 1.8,
2, 2.5, 3.3 or 5 Volts
Maximum Rated Output
Current in Amps
RoHS-6
compliant*
Heat Sink option
Surface-Mount Package
Blank
= Through-hole package
Input Voltage Range:
D12
= 10.2 to 13.8 Volts
(12V nominal)
SMT LEADS COPLANAR
TO 0.004 (0.10)
0.150
(3.81)
0.125
(3.18)
1
6
7
8
9
10
0.035
(0.89)
0.600
(15.24)
2
3
4
5
0.90
(22.86)
Note:
Not all model number combinations
are available. Contact MPS.
*
Contact Murata Power Solutions
(Datel) for availability.
0.150 TYP.
(3.81)
BOTTOM VIEW
DIMENSIONS ARE IN INCHES (MM)
0.110
(2.79)
0.50 (12.7)
W/ HEATSINK
0.46 (11.68)
WO/ HEATSINK
Case C44
2.23 (56.64)
A
I/O Connections
Pin Function P62
1
Common
2
V
OUT
Trim
3
NC
4 On/Off control
5
+Input
Pin
6
7
8
9
10
Function P62
Common
+Output
Common
+Output
+Sense
0.200 MIN.
(5.08)
0.122
(3.10)
PLASTIC STANDOFFS
ARE RELIEVED 0.030 (0.76)
IN SOLDER JOINT AREA
PINS 2-4, 10:
0.040 ±0.001
(1.016 ±0.025)
PINS 1, 5-9:
0.062 ±0.001
(1.575 ±0.025)
2.00 (50.80)
B
A
B
1
2
3
4
5
BOTTOM VIEW
6
7
8
9
10
0.90
(22.86)
Component locations are typical and may vary with different models.
0.600 (15.24)
4 EQ. SP. @ 0.150 (3.81)
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+1 508 339 3000
MDC_LEN D12 Models.B01 Page 2 of 10
LEN-D12 Models
Performance/Functional Specifications
Typical @ T
A
= +25°C under nominal line voltage and full-load conditions unless noted.
Input
Non-Isolated, 28A Eighth Brick
DC/DC Converters
Absolute Maximum Ratings
Input Voltage Range
Input Current:
Normal Operating Conditions
Inrush Transient
Standby/Off Mode
Output Short-Circuit Condition
Input Reflected Ripple Current
Input Filter Type
Overvoltage Protection
Reverse-Polarity Protection
Undervoltage Shutdown
On/Off Control
10.2-13.8 Volts (12V nominal)
See Ordering Guide
TBD
3.5mA
130mA
20mAp-p
Capacitive (66μF)
14.3 Volts
None
9.4 Volts
On = open or 0 to +0.4V
Off = +2.8V to +V
IN
(<3mA)
Output
Input Voltage:
Continuous or transient
On/Off Control (Pin 11)
Input Reverse-Polarity Protection
Output Overvoltage Protection
Output Current
Storage Temperature
Lead Temperature (soldering, 10 sec.)
15.5 Volts
+V
IN
None
V
OUT
+20%
Current limited. Devices can
withstand sustained output
short circuits without damage.
–55 to +125°C
+300°C
V
OUT
Accuracy
(50% load)
Minimum Loading
Maximum Capacitive Load
V
OUT
Trim Range
±1.5% maximum
No load
10,000μF (low ESR, OSCON)
±10% for V
OUT
=
≥1.8V
+10%/–3% for V
OUT
1.5V and lower
(no trim for 0.8V models)
See Ordering Guide
3% over line/load temperature
See Ordering Guide
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.
TECHNICAL NOTES
Ripple/Noise
(20MHz BW)
Total Accuracy
Efficiency
Overcurrent Detection and Short-Circuit Protection:
Current-Limiting Detection Point
35 Amps
Short-Circuit Detection Point
98% of V
OUT
set
SC Protection Technique
Hiccup with auto recovery
Short-Circuit Current
TBD
Dynamic Characteristics
Return Current Paths
The LEN D12 are non-isolated DC/DC converters. Their Common pins (pins 1,
6 and 8) 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 1 (also referred to as –Input or Input Return),
and output return current should be directed through pin 6 and 8 (also referred
to as –Output or Output Return). Any on/off control signals applied to pin 4
(On/Off Control) should be referenced to Common (specifically pin 1).
I/O Filtering and Noise Reduction
All models in the LEN D12 Series are tested and specified with external 33μF
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 LEN D12s are designed with high-quality,
high-performance internal I/O caps, and will operate within spec in most applica-
tions with
no additional external components.
In particular, the LEN 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 33μF 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/DCs requires that the dc input voltage source
have low ac impedance and the frequencies of interest. Highly inductive
source impedances can greatly affect system stability. Your specific system
configuration may necessitate additional considerations.
Transient Response
(25% load step) 100μsec to ±2% of final value
Start-Up Time:
V
IN
to V
OUT
and On/Off to V
OUT
Switching Frequency
20ms
320kHz ±40kHz
Environmental
Calculated MTBF
Operating Temperature:
(Ambient)
Without Derating (With 200 lfm)
With Derating
Thermal Shutdown
TBD million hours
–40 to +65°C (model dependent)
See Derating Curves
+125°C
Physical
Dimensions
Pin Material
Weight
Flamability Rating
See Mechanical Dimensions
Gold-plated copper alloy with nickel underplate
0.6 ounces (17g)
UL94V-0
All models are tested and specified with external 33μF 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.
Input Ripple Current is tested/specified over a 5-20MHz bandwidth with an external 33μF input
capacitor and a simulated source impedance of 220μF and 12μH. See I/O Filtering, Input Ripple
Current and Output Noise for details.
The On/Off Control (pin 4) is designed to be driven with open-collector logic or the application of
appropriate voltages (referenced to Common, pins 1, 6 and 8).
Output noise may be further reduced with the installation of additional external output filtering.
See I/O Filtering and Noise Reduction.
MTBF’s are calculated using Telcordia SR-332(Bellcore), ground fixed, T
A
= +25°C, full power,
natural convection, TBD pcb temperature.
See Performance Specifications, note 6.
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MDC_LEN D12 Models.B01 Page 3 of 10
LEN-D12 Models
Non-Isolated, 28A Eighth Brick
DC/DC Converters
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 appropriate fre-
quency 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 func-
tion of your line voltage and source impedance, as well as your particular load
and layout conditions. Our Applications Engineers can recommend potential
solutions and discuss the possibility of our modifying a given device’s internal
filtering to meet your specific requirements. Contact our Applications Engineer-
ing Group for additional details.
Input Fusing
Most applications and or safety agencies require the installation of fuses at the
inputs of power conversion components. LEN D12 Series DC/DC converters are
not internally fused. Therefore, input fusing is mandatory for safety reasons, and
safety agencies require a time delay fuse with a value no greater than 40 Amps,
which 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.
Safety Considerations
LEN D12'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 specifications (usually
UL/IEC/EN60950-1).
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.
Start-Up Time
The V
IN
to V
OUT
Start-Up Time is the interval between the time at which a ramp-
ing input voltage crosses the lower limit of the specified input voltage range
(10.2 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 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
LEN D12 Series DC/DC converters offer an output sense function on pin 10.
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 conse-
quently 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 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 functions
can cause the output voltage to increase, thereby increasing output power
beyond the converter's specified rating. Therefore:
(V
OUT
at pins) x (I
OUT
)
≤
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:
If devices have the +Sense pin (pin 10) installed (no part-number
suffix) and the sense function is not used for remote regulation, +Sense
(pin 10) must be tied to +Output (pin 7, 9) at the DC/DC converter pins.
On/Off Control
The On/Off Control pin may be used for remote on/off operation. LEN D12
Series DC/DC converters are designed so that they are enabled when the
control pin is left open (or pulled low to 0 to +0.4V) and disabled when the
control pin is pulled high (+2.8V to +V
IN
). As shown in Figure 2, all models have
an internal 20kΩ pull-down resistor to Common (ground).
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MDC_LEN D12 Models.B01 Page 4 of 10
LEN-D12 Models
Non-Isolated, 28A Eighth Brick
DC/DC Converters
+INPUT
2.5V
Optional
Pullup
10k
ON/OFF
CONTROL
+
–
20k
Small
Signal
Transistor
COMMON
Output Overvoltage Protection
The LEN D12 Series output voltage is monitored. If the output voltage rises
to a level, which could be damaging to the load, the internal sensing circuitry
will power down the PWM controller causing the output voltage to decrease.
Following a time-out period the PWM will restart, causing the output voltage
to ramp to its appropriate value. If the fault condition persists, and the output
voltage again climbs to excessive levels, the overvoltage circuitry will initiate
another shutdown cycle. This on/off cycling is referred to as "hiccup" mode.
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. LEN D12 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 40% (35 Amps)
or if the output voltage drops to less than 98% of it original value, the LEN
D12's internal overcurrent-detection circuitry immediately turns off the con-
verter, 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, both the average output current and the average
input current will be kept extremely low. Once the output short is removed, the
converter will automatically restart itself.
Output Voltage Trimming
Allowable trim ranges for models
≥1.8V
OUT
are ±10%, and for models 1.5V
OUT
and lower +10%/–3% (no trim for 0.8V models). 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 4.
ON/OFF pin open: Logic Low = DC/DC converter On
ON/OFF pin >2.8V: Logic High = DC/DC converter Off
Figure 2. Driving the On/Off Control Pin
Dynamic control of the on/off function is best accomplished with a
mechanical relay or open-collector/open-drain drive circuit (optically isolated if
appropriate). The drive circuit should be able to sink appropriate current when
activated and withstand appropriate voltage when deactivated.
The on/off control can be driven using a circuit comparable to that shown in
Figure 2. Leaving the On/Off control pin open or applying a voltage between 0V
and +0.4V will turn on the converter. Applied voltages between +2.8V and +V
IN
will disable the converter.
Power-up Sequencing
If a controlled start-up of one or more LEN 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 pulled high to +V
IN
with an external
5.6kΩ restistor. While input voltage and/or other converters are ramping up,
the control pin is pulled high and the converter remains disabled. To enable
the output voltage, the control pin needs to be pulled low in the configuration
shown in Figure 3.
+INPUT
2.5V
5.6k
ON/OFF
CONTROL
+
–
20k
COMMON
External Input Open: On/Off pin High = DC/DC converter Off
External Input Low: On/Off pin Low = DC/DC converter On
Figure 4. Trim Connections Using a Trimpot
Figure 3. Driving The Power-Up With An External Pull-up Resistor
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MDC_LEN D12 Models.B01 Page 5 of 10
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