+INPUT
(5)
COMMON
(1)
2-PHASE
PWM
CONTROLLER
CURRENT
SENSE
REFERENCE &
ERROR AMP
VCC
ON/OFF
CONTROL
(4)
VOUT
TRIM
(2)
+OUTPUT
(7,9)
+SENSE
(10)
COMMON
(6, 8)
Single Output
HEN D12 Models
Non Isolated, 12VIN, 0.8-5VOUT
25 Amp, High di/dt DC/DC Converters
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
The HEN D12 Series of non-isolated eighth bricks with high di/dt 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.
HEN D12 DC/DC's 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, 3.3
or 5 Volt output fully rated at 25 Amps.
HEN D12's are ideal POLPP's (point-of-use/load power processors) and they
typically require 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 0.39 inches (0.5" including optional heat sink).
The HEN's best-in-class power density is achieved with a fully synchronous,
fixed-frequency, 2-phase buck topology that delivers extremely high efficiency (92.5%
for 5VOUT models), low noise (10mVp-p typ.), extremely tight line/load regulation
(±0.05%/0.1%max.), fast transient response (50A/µsec with full-load step), stable
no-load operation, and no output reverse conduction.
The fully functional HEN's feature input over/undervoltage lockout, output over-
voltage and overcurrent detection, continuous short-circuit protection, overtempera-
ture protection, an output-voltage trim function, a remote on/off control pin, and a
sense pin. High efficiency enables the HEN D12's 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, DATEL's non-isolated ¼- and 1/8-brick's will save you money.
➀ Only one phase of two shown.
➀
Features
■
■
■
■
■
■
■
■
■
■
■
■
■
■
Eighth brick, through hole or SMT
with fast transient response
2-phase buck regulators for new
distributed 12V power architectures
12V input (10.2-13.8V range)
0.8/1/1.2/1.5/1.8/2/2.5/3.3/5VOUT @ 25A
Non-isolated, fixed-frequency,
synchronous-rectifier topology
Efficiencies to 92.5% @ 25 Amps
Noise as low as 10mVp-p
Stable no-load operation
On/Off control, trim & sense functions
Output Overvoltage Protection
Input Over/Undervoltage lockout
Thermal shutdown
Designed to meet UL/EN/IEC60950
EMC compliant
PRELIMINARY
®®
A SUBSIDIARY OF C&D TECHNOLOGIES
HEN D12 Series N O N - I S O L A T E D , 2 5 A E I G H T H B R I C K , D C / D C C O N V E R T E R S
HEN-0.8/25-D12 ➄ 0.8 25 10 20 ±0.05% ±0.1% 12 10.2-13.8 TBD/2.1 77.5% 80.5% C47,C48, P62
HEN-1/25-D12 ➄ 1 25 10 20 ±0.05% ±0.1% 12 10.2-13.8 TBD/2.5 79.5% 82.5% C47,C48, P62
HEN-1.2/25-D12 1.2 25 10 20 ±0.05% ±0.1% 12 10.2-13.8 160/2.9 82% 85% C47,C48, P62
HEN-1.5/25-D12 1.5 25 10 20 ±0.05% ±0.1% 12 10.2-13.8 160/3.6 84% 87% C47,C48, P62
HEN-1.8/25-D12 ➄ 1.8 25 10 20 ±0.05% ±0.1% 12 10.2-13.8 TBD/4.3 84.5% 88% C47,C48, P62
HEN-2/25-D12 ➄ 2 25 10 20 ±0.05% ±0.1% 12 10.2-13.8 TBD/4.7 85.5% 88.5% C47,C48, P62
HEN-2.5/25-D12 ➄ 2.5 25 10 20 ±0.05% ±0.1% 12 10.2-13.8 TBD/5.8 86.5% 90% C47,C48, P62
HEN-3.3/25-D12 ➄ 3.3 25 10 20 ±0.05% ±0.1% 12 10.2-13.8 TBD/7.5 88.5% 91.5% C47,C48, P62
HEN-5/25-D12 ➄ 5 25 10 20 ±0.05% ±0.1% 12 10.2-13.8 TBD/11.3 89.5% 92.5% C47,C48, P62
➀ Typical at TA = +25°C under nominal line voltage and full-load conditions, unless otherwise
noted. All models are tested and specified with an external 33µF input and output capacitors.
These capacitors are necessary to accomodate our test equipment and may not be required
to achieve performance in your application. All models are stable and regulate within spec
under no-load conditions.
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 availability.
➅ The operating input voltage is 10.2V to 13.8V. However, 10.8VIN 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.
MECHANICAL SPECIFICATIONS
PART NUMBER STRUCTURE
Performance Specifications and Ordering Guide ➀
VOUT IOUT VIN Nom. Range ➅ IIN ➃ Package
Model (Volts) (Amps) Typ. Max. Line Load (Volts) (Volts) (mA/A) Min. Typ. (Case, Pinout)
Output Input Efficiency
Full Load
I/O Connections
Maximum Rated Output
Current in Amps
Non-Isolated Eighth Brick
Output
Configuration:
H = Unipolar
High di/dt
Nominal Output Voltage:
0.8, 1, 1.2, 1.5, 1.8, 2, 2.5, 3.3
or 5 Volts
Input Voltage Range:
D12 = 10.2 to 13.8 Volts
(12V nominal)
H EN 25-/D12-1.8
Surface-Mount Package
M
Case C48
Case C47
2
Heat Sink Option
H
See Heatsink Installation and Automated Assembly and Production Notes for details
R/N (mVp-p) ➁ Regulation (Max.) ➂
Pin Function P62 Pin Function P62
1 Common 6 Common
2 VOUT Trim 7 +Output
3 NC 8 Common
4 On/Off Control 9 +Output
5 +Input 10 +Sense
HEN D12 Models
N O N - I S O L A T E D , 2 5 A E I G H T H B R I C K , D C / D C C O N V E R T E R S
Input
Input Voltage Range 10.2-13.8 Volts (12V nominal) ➉
Input Current:
Normal Operating Conditions See Ordering Guide
Inrush Transient ➆ 0.04A2sec maximum
Standby/Off Mode 41mA
Output Short-Circuit Condition 250mA
Input Reflected Ripple Current ➁ 25mAp-p
Input Filter Type Capacitive
Overvoltage Protection 14.3 Volts
Reverse-Polarity Protection None
Undervoltage Shutdown 9.5 Volts
No-Load Input Current 160mA
Remote On/Off Control: ➄ On = open (internal pull down), 0 to +0.8V
Off = +2.5V to +VIN or pulled high
Remote Control On/Off Current 0.75mA maximum
Remote Sense Input Range ±10% of VOUT
Output
VOUT Accuracy (50% load) ±1.5%
Minimum Loading ➀ No minimum load
Maximum Output Power ➇ 30.45W (1.2V), 38.06W (1.5V models)
Maximum Capacitive Loading 40,000µF (electrolytic, ESR <10mΩ)
VOUT Trim Range ➇ ±10%
Ripple/Noise (20MHz BW) See Ordering Guide
Total Accuracy ±3% over line, load and temperature
Temperature Coefficient at All Outputs ±0.02%/°C
Efficiency See Ordering Guide
Overcurrent Detection and Short-Circuit Protection:
Current-Limiting Detection 42 Amps, cold startup (35A after warmup)
Short-Circuit Protection Method ➈ Hiccup with auto recovery
Short-Circuit Current ➅ 2.5A, 4A maximum average
Short-Circuit Duration Continuous, output shorted to ground
Dynamic Characteristics
Transient Response:
(50-100% load step to±1.5%VOUT) 30µsec typical, 60µsec maximum
Start-Up Time:
VIN to VOUT or On/Off to VOUT 10msec maximum for VOUT = nominal
Switching Frequency 660kHz ±10%
Environmental
Calculated MTBF ➃ TBD million hours
Operating Temperature: (Ambient)
100 lfm Airflow, Full Power –40 to +60°C (model dependent)
With Derating See Derating Curves
Storage Temperature Range –55 to +125°C
Thermal Protection Shutdown +119°C
Altitude 0 to 10,000 feet
Relative Humidity 10 to 90% non-condensing
Physical
Dimensions See Mechanical Specifications
Pin Material Copper with tin-lead plate over nickel
Weight 0.6 ounces (17g)
Flamability Rating UL94V-0
Electromagnetic Interference Conducted and radiated to FCC part
EN55022 Class A
Safety UL/cUL/IEC/EN 60950, CSA-C22.2 #234
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 an external 33µF tantalum input capacitor and
3000µF POSCAP and 300µF ceramic external output capacitors except where noted.
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 specified with no external filter.
➂ Current Limit Inception is given at either cold startup or after warmup.
➃ MTBF is calculated using Telcordia (Bellcore) SR-332, Method 1, Case 3, ground-fixed
conditions, TCASE = +25°C, full load, natural convection, +67°C maximum pcb temperature.
➄ The On/Off Control (pin 4) may be driven with open-collector logic or the application of
appropriate voltages (referenced to Common, pin 1).
➅ The short circuit current is an average which includes brief, full-current hiccup pulses.
➆ Startup inrush current should be used to compute proper external fusing, if installed. The
fuse rating will depend on the fuse thermal time constant ("slow blow"), and other factors.
➇ VOUT times IOUT must not exceed maximum power.
➈ See Technical Notes.
➉ See note 6, page 2.
T E C H N I C A L N O T E S
Input Voltage:
Continuous 14 Volts
Transient (100msec maximum) 15 Volts
On/Off Control (Pin 4) +VIN
Input Reverse-Polarity Protection None
Output Overvoltage Protection VOUT +20%
Output Current Current limited. Devices can
withstand sustained output short
circuit without damage.
Storage Temperature –55 to +125°C
Lead Temperature (soldering, 10 sec.) +300°C (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 or recommended.
Absolute Maximum Ratings
3
Return Current Paths
The HEN 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 HEN 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 HEN 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 HEN 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.
HEN D12 Series N O N - I S O L A T E D , 2 5 A E I G H T H B R I C K , D C / D C C O N V E R T E R S
4
Figure 2. Driving the On/Off Control Pin
ON/OFF pin open: Logic Low = DC/DC converter On
ON/OFF pin >2.8V: Logic High = DC/DC converter Off
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 and 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
appropriate 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. HEN 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 40Amps, 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
HEN 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/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.
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 (10.2 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 VOUT Start-Up Time assumes the converter is turned off via
the On/Off Control with the nominal input voltage already applied to the con-
verter. 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
HEN 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
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 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
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 converter's specified rating. Therefore:
(VOUT at pins) x (IOUT) ≤ rated output power
The internal 10Ω 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. HEN D12
Series DC/DC converters are designed so that they are enabled when the
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HEN D12 Models
N O N - I S O L A T E D , 2 5 A E I G H T H B R I C K , D C / D C C O N V E R T E R S
Figure 5. Trim Connections Using Fixed Resistors
Figure 4. Trim Connections Using a Trimpot
�
Note:
Install either a fixed
trim-up resistor
or a fixed trim-down
resistor depending upon
desired output voltage.
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.
5
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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 +VIN). As shown in Figure 2, all models
have an internal 20kΩ pull-down resistor to Common (ground).
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.
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
+VIN will disable the converter.
Power-up sequencing
If a controlled start-up of one or more HEN 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 +VIN with an external
5.6kΩ resistor. 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.
Output Overvoltage Protection
The HEN 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. HEN 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 HEN
D12's internal overcurrent-detection circuitry immediately turns off the
+INPUT
COMMON
ON/OFF
CONTROL
2.5V
+
–
5.6kΩ
20kΩ
Figure 3. Driving The Power-Up With An External Pull-up Resistor
External Input Open: On/Off pin High = DC/DC converter Off
External Input Low: On/Off pin Low = DC/DC converter On
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, 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 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 4 below.
A trimpot can be used to determine the value of a single fixed resistor
which can then be connected, as shown in Figure 5, 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 ±1.5% accurate.
Adjustment beyond the specified ±10% adjustment range is not recommended.
HEN D12 Series N O N - I S O L A T E D , 2 5 A E I G H T H B R I C K , D C / D C C O N V E R T E R S
Typical Performance Curves for HEN 1.2V Models
6
HEN D12 Models
N O N - I S O L A T E D , 2 5 A E I G H T H B R I C K , D C / D C C O N V E R T E R S
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.
HEN D12 DC/DC converters do not suffer from Output Reverse Conduction.
They employ proprietary gate drive circuitry that makes them immune to
applied output voltages.
Typical Performance Curves for HEN 1.5V Models
7
HEN D12 Series N O N - I S O L A T E D , 2 5 A E I G H T H B R I C K , D C / D C C O N V E R T E R S
8
Heatsink Installation
Heatsinks, in combination with adequate airflow, significantly extend the
power-handling capability of DATEL power supplies and add a safety margin.
Please study the Derating Curves to understand the increased thermal
capacity available when a heatsink is installed.
DATEL will supply our custom-designed heatsinks already installed. If
preferred, users may also purchase the heatsink assembly separately. If so,
please carefully follow the installation instructions below to avoid damage to
the DC/DC converter. Contact DATEL if you need assistance. The following
procedures require adequate mechanical skills.
Installation has several goals:
1. Insure positive thermal contact between heat-generating circuit
components and the heatsink.
2. Avoid mechanical stress to the printed circuit board and on-board
components.
3. Fasten the heatsink securely so that vibration in the application will not
loosen the mounting screws. Note that some heat may be conducted
through the screws.
4. Avoid stripping threads in the aluminum heatsink.
Thermal Pads
The heatsink is supplied with one or more thermal mounting pads which
provide a heat transfer path with low thermal resistance between power com-
ponents and the heatsink. DATEL does NOT recommend "thermal grease" or
thermal mounting compounds.
Mounting Screws
DATEL power supplies are precision miniature electronic assemblies
fabricated on multiple circuit board layers. Excessive pressure or incorrect
mechanical stress may distort the board layers, apply too much force on
components or even break small connections. Such fractures may not be
visible with the naked eye. It is very important to use the assembly sequence
below. We want both a correct sequence and the right amount of torque. This
assembly sequence is similar to engine cylinder heads (progressive torquing
of diagonally alternating bolts).
A tiny amount of medium-strength (blue) Loctite ® thread assembly adhesive
or equivalent is acceptable in high vibration applications. The threads must
be degreased for Loctite to work. Do not soak the threads with Loctite. Also,
be aware that Loctite will soften at higher temperatures.
Correct assembly requires a precision low range torque wrench.
[1] Make sure all the thermal pads have been securely installed. Mount the
heatsink using the screws supplied. See the assembly diagram. Do not
tighten the screws yet.
[2] Tighten the first screw only to 50% of maximum final torque (see the
table below).
[3] Tighten the screw in the diagonally opposite corner to 50% torque.
[4] Tighten the screw adjacent to the first screw to 50% torque.
[5] Repeat steps [2] to [4], tightening all screws to their maximum torque.
[6] Thoroughly retest the power supply before committing it to application.
WARNING: Incorrect assembly sequence and/or excessive torque may
damage the converter.
For attachment screws, the following maximum final torques must be used:
Screw Size Maximum Assembled Torque
#2-56 thread 2.5 inch-pounds maximum
#4-40 thread 5.5 inch-pounds maximum
#M3 thread 6.0 inch-pounds maximum
#6-32 thread 9.6 inch-pounds maximum
HEN D12 Models
N O N - I S O L A T E D , 2 5 A E I G H T H B R I C K , D C / D C C O N V E R T E R S
Automated Assembly Production Notes
DATEL’s new high-efficiency DC/DC converters are designed for modern
surface-mount technology (SMT) automated assembly using screened solder
paste, "pick and place" component positioning and forced hot air reflow oven
soldering. If you are new to SMT techniques and have a volume applica-
tion, these features save time, cost and improve manufacturing efficiency.
DATEL’s DC/DC assembly operations themselves make extensive use of
such techniques.
Even if you have previous SMT experience, you should read the sections
below on solder reflow profiles and heat shields. This information is not
intended to replace the documentation for your SMT system. We assume that
you are already experienced with all the components of your SMT system.
This section will discuss several SMT issues, including:
I/O Mechanical Configuration
Part Handling and Supply
Printed Circuit Board (pcb) Mounting
Soldering using Reflow Technology
Temperature Profiling
Heat Shields and Removal
Mechanical Configuration of Input/Output Connections
These new converters are supplied either using traditional through-hole pins
or SMT leads. (Note that some models are offered only with lead mounting).
The pin options insert into plated-through holes in the host pcb. Be aware
that some heat dissipation is carried off by either the pins or leads. The
Derating Curves assume that some additional pad area is available on your
host pcb to absorb the heat.
The lead option uses either short tabs in "gullwing" style or standoff leads
under the converter. The gullwing leads typically are copper alloy with 150
microinches of tin plating. Solder paste (typically 0.008" to 0.009" thick) is
applied to the host pcb using a solder mask pressure screening technique
and the board is heated and cooled long enough for the solder to reflow and
adhere to both the host pads and the converter’s mounting leads.
After such mounting, the entire mechanical mounting load is carried by the
solder. Obviously the converters must be accurately positioned all during the
solder reflow period. Where solder surface tension is sufficient to force tiny
components into position, these larger converters may not move and must be
accurately positioned by your SMT system.
Part Handling and Supply
SMT eighth- and quarter-brick DC/DC converters (plus installed heat shields
if used) are supplied in JEDEC-standard 5.35" by 12.4" waffle trays which are
compatible with the feeders on industry-standard pick-and-place machines.
Since the converters are larger and heavier than many other components,
make sure your system can reliably remove the units from their trays, move
them to the host pcb and accurately position them. The plastic heat shield
(see below) doubles as a vacuum pickup area.
Heatsinks
If you are using the preinstalled heatsink from DATEL, proceed normally
with surface mounting per the information in this section (the heat shield
fits completely over the heatsink). However, if you wish to add the heatsink
after receiving the converters and heatsink separately, you must install the
heatsink before solder reflow. Essentially, install the heatsink then place the
assembled converters back in the tray for surface mount positioning. Please
observe the torquing and assembly procedure discussed earlier for the
heatsink.
Pick and Place pcb Mounting
The main issues here are pad area, orientation, positioning accuracy,
vacuum pickup and coplanarity. DATEL recommends that pcb pads to
interface with the DC/DC converter should be sized as shown in the diagram
below. The pads footprint accommodates the positioning accuracy of your
SMT equipment and manufactured tolerances of the DC/DC mounting leads.
Orientation: When loaded into JEDEC trays, these converters are all
oriented in the same direction. See the diagram below. For the LEN and
HEN series, a notch is placed on the top of the case (on the removal tabs) to
indicate the pin 1 position. You should visually inspect the tray to be sure of
this orientation.
On the bottom of the converter, the LEN and HEN series include optical fidu-
cial marks viewable by your SMT imaging system. See the attached diagram.
Observing from the bottom, your SMT imaging camera should find these
marks to identify the converter and verify pin 1. On most pick-and-place
systems, during head transit, the imaging system will automatically fine tune
the end mounting position of the converter using image comparisons from
these fiducials or other reference marks you have chosen.
The fiducial marks are placed fairly close together because most imaging
systems have a one inch or less observing area since most SMT parts are
considerably smaller than these converters. You may prefer to train your
imaging system to use a corner of the converter or an I/O lead.
In the drawing below, these dimensions are intended for initial search for
these marks by your camera. There will be tiny variations in absolute position
from unit to unit.
9
Figure 6. Recommended SMT Mounting Pad Dimensions
HEN D12 Series N O N - I S O L A T E D , 2 5 A E I G H T H B R I C K , D C / D C C O N V E R T E R S
If you use a camera above the pcb after placement on the solder paste, do
not rely on the inkjet marking on the heat shield to verify proper orientation.
Use the pin 1 notch instead.
Coplanarity: DATEL manufactures these converters with very flat mounting
leads (see coplanarity specs) however your host pcb must also be flat for a
successful mounting. Be aware of possible warping of the pcb under heat
gradients and/or humidity conditions. The solder paste will tolerate a small
amount of mismatch and will tend to “wet” the entire pad area by capillary
action if the temperatures are correct.
Vacuum Pickup: Select the vacuum collet on your SMT placement system
for the weight and size of the DC/DC converter. Note that units with heatsinks
are slightly heavier. Tests at DATEL have shown that excellent acceleration
and transit head speed are available for these converters if the collet size is
proper and the vacuum is sufficient. When positioning the vacuum collet, use
the geometric center of the heat shield as the pickup area since the center of
gravity is very close.
Soldering
Reflow technology works well for small parts. However, larger components
such as these DC/DC’s with higher thermal mass may require additional
reflow time (but not enough to disturb smaller parts also being reflowed con-
currently with the DC/DC). When this is combined with higher temperature
lead-free solders (or solders with reduced heavy metals), there is increased
risk of reheating components inside the DC/DC enough so that they either
change positions (and possibly stop functioning) or the components are
damaged by the heat.
For these reasons, DATEL developed disposable heat shields using high
temperature plastic. The DC/DC is installed and reflowed with the shield in
place. After successful reflow and cooling, and before washing, the heat
shield should be removed.
Temperature Profiling
We wish to ramp the temperature up and down to successfully reflow the
solder without heat damage. Each reflow oven, humidity conditions, solder
paste type, oven feed rate, and the number of heat zones all require a differ-
ent profile. Therefore you may have to experiment.
Since these converters are constructed using high temperature solders, there
will be no heat problems on your host pcb using traditional solder with 63%
lead and 37% tin with a melting point of +183°C. Device lead temperature
must remain below 230°C for less than 75 seconds, assuming that the heat
shield is in place. DATEL uses a 216°C melt lead-free tin/silver/copper alloy
to assemble these converters.
There are several lead-free solders suitable for your host pcb depending on
your SMT system and whatever local certification and environmental regula-
tions you must observe. Contact DATEL if you need specific advice.
Heat Shield
Careful thermocouple testing has shown that the interior of the DC/DC under
the heat shield is tens of degrees cooler than the outside ambient tempera-
ture for typical reflow profiles. This protects internal components and limits
the amount of reflow where it is not desired. The heat shield also includes
marking for product identification and a date/lot code.
On LEN and HEN models, the heat shield is attached to the converter using
molded plastic pins on the heat shield interior which insert into recessed
dimples in the pinframe. An extra molded pin on the heat shield at the pin 1
location (and corresponding notch on the pcb) can only be installed one way
properly on the pinframe. If the shield accidentally comes loose, it may be
reinstalled by aligning the pins and dimples.
To remove the shield from the converter, after successful mounting and cool-
ing, squeeze the heat shield ears inward toward the converter body and pull
the shield upwards. Discard or recycle the shield. If you are using a flux wash
cycle, remove the heat shield before washing to avoid coming loose inside
the washer.
Figure 7. Fiducial Mark Location
10
HEN D12 Models
N O N - I S O L A T E D , 2 5 A E I G H T H B R I C K , D C / D C C O N V E R T E R S
DS-0533 07/04
11
Figure 8. Shipping Tray
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
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Internet: www.datel-europe.com E-mail: datel.sarl@datel.com
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Internet: www.datel-europe.com E-mail: datel.gmbh@datel.com
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Internet: www.datel.co.jp Email: salestko@datel.co.jp, salesosa@datel.co.jp
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E-mail: davidx@datel.com
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Tel: (508) 339-3000 (800) 233-2765 Fax: (508) 339-6356
www.datel.com Email: sales@datel.com
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