NEW
Wide-Input-Range
"Q" Models
®
®
A SUBSIDIARY OF C&D TECHNOLOGIES
Single Output
UHE Models
Isolated, High Efficiency, 1.6" x 2"
2-10 Amp, 12-30 Watt DC/DC's
Features
The most I
OUT
/P
OUT
in this format
Lower priced than bricks
Small 1.6" x 2" x 0.4" plastic package
with standard 2" x 2" pinout
Output configurations:
1.2/1.5/1.8/2.5V
OUT
@ 10 Amps
3.3/5V
OUT
@ 25 Watts
5/12/15V
OUT
@ 30 Watts
Five input ranges from 9-75 Volts
Efficiencies as high as 91.5%
Stable no-load operation
Optional Sense pins for low V
OUT
Thermal shutdown, I/O protected
1500 Vdc I/O BASIC Insulation
UL/EN60950 certified; CE marked
for Q48 models
Housed in smaller, 1.6" x 2" x 0.40" (41 x 51 x 10.2mm) packages carrying the
standard 2" x 2" pinout, DATEL's new UHE Series DC/DC Converters deliver more
current/power (up to 10A/30W) than currently available from either package size.
The UHE 12-30W Series of high-efficiency, isolated DC/DC's provide output power
ranging from 10 Amps @ 1.2V to 2 Amps @ 15V. Offering both 2:1 and 4:1 input
voltage ranges, UHE's meet V
IN
requirements from 9 to 75 Volts.
Taking full advantage of the synchronous-rectifier, forward topology, UHE's boast
outstanding efficiency (some models exceed 91%) enabling full-power operation to
ambient temperatures as high as +60°C, without air flow. Assembled using fully
automated, SMT-on-pcb techniques, UHE's provide stable no-load operation, excel-
lent line (±0.1%) and load (±0.15%) regulation, quick step response (200µsec), and
low output ripple/noise (50-100mVp-p). Additionally, the UHE's unique output design
eliminates one of the topology's few shortcomings–output reverse conduction.
All devices feature full I/O fault protection including: input overvoltage and under-
voltage shutdown, precise output overvoltage protection (a rarity on low-voltage
outputs), output current limiting, short-circuit protection, and thermal shutdown.
All UHE models incorporate a V
OUT
Trim function and an On/Off Control pin
(positive or negative polarity). Low-voltage models (1.2V to 5V) offer optional sense
pins facilitating either remote load regulation or current sharing for true N+1 redun-
dancy. All models are certified to the BASIC insulation requirements of UL/EN60950,
and 48V
IN
(75V max.) models carry the CE mark.
+INPUT
(1)
+OUTPUT
(6)
SWITCH
CONTROL
+SENSE
(5)
➁
➀½½
THERMAL
SHUTDOWN
OPTO
ISOLATION
OVERVOLTAGE
COMPARATOR
–OUTPUT
(7)
–INPUT
(2)
–SENSE
(8)
➁
PWM
CONTROLLER
UVLO & OVLO
COMPARATORS
ON/OFF
CONTROL
(4)
OPTO
ISOLATION
REFERENCE &
ERROR AMP
V
OUT
TRIM
(9)
➀
Optional comparator feedback. Contact DATEL.
➁
Sense pins are optional on 1.2-5V
OUT
models ("R" suffix).
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
XHE Series
Performance Specifications and Ordering Guide
Output
Model
UHE-1.2/10000-D12
UHE-1.2/10000-D24
UHE-1.2/10000-D48
UHE-1.5/10000-D12
UHE-1.5/10000-D24
UHE-1.5/10000-D48
UHE-1.8/10000-D12
UHE-1.8/10000-D24
UHE-1.8/10000-D48
UHE-2.5/10000-D12
UHE-2.5/10000-D24
UHE-2.5/10000-D48
UHE-3.3/7500-Q12
UHE-3.3/7500-Q48
UHE-3.3/7500-D48
UHE-3.3/7500-D48T
UHE-5/5000-Q12
UHE-5/5000-Q48
UHE-5/6000-D48
UHE-5/6000-D48T
UHE-5/6000-Q48T
UHE-12/2500-Q12
UHE-12/2500-D12
UHE-12/2500-D24
UHE-12/2500-Q48
UHE-12/2500-D48
UHE-15/2000-D12
UHE-15/2000-Q12
UHE-15/2000-D24
UHE-15/2000-Q48
UHE-15/2000-D48
1 2 - 3 0 W, S I N G L E O U T P U T D C / D C C O N V E RT E R S
➀
Input
Regulation (Max.)
Line
Load
➂
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.05%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.15/0.625%
±0.15/0.625%
±0.15/0.625%
±0.15/0.625%
±0.15/0.625%
±0.15/0.625%
±0.15/0.625%
±0.15/0.625%
±0.15/0.625%
±0.15/0.5%
±0.15/0.5%
±0.15/0.5%
±0.15/0.3%
±0.15/0.3%
±0.15/0.3%
±0.25%
±0.15/0.3%
±0.15/0.3%
±0.25/0.5%
±0.25%
±0.45%
±0.3%
±0.3%
±0.3%
±0.3%
±0.3%
±0.3%
±0.5%
±0.3%
±0.3%
±0.3%
V
OUT
(Volts)
1.2
1.2
1.2
1.5
1.5
1.5
1.8
1.8
1.8
2.5
2.5
2.5
3.3
3.3
3.3
3.3
5
5
5
5
5
12
12
12
12
12
15
15
15
15
15
I
OUT
(Amps)
10
10
10
10
10
10
10
10
10
10
10
10
7.5
7.5
7.5
7.5
5
5
6
6
6
2.5
2.5
2.5
2.5
2.5
2
2
2
2
2
R/N (mVp-p)
➁
Typ.
Max.
80
80
80
55
55
55
55
55
50
50
50
50
50
60
60
80
50
60
80
80
90
100
65
65
100
60
70
70
70
100
70
120
120
120
80
80
80
80
80
75
75
75
75
70
90
90
100
70
90
100
100
125
120
100
100
120
100
100
100
100
150
100
V
IN
Nom.
(Volts)
12
24
48
12
24
48
12
24
48
12
24
48
24
48
48
48
24
48
48
48
48
24
12
24
48
48
12
24
24
48
48
Range
(Volts)
9-18
18-36
36-75
9-18
18-36
36-75
9-18
18-36
36-75
9-18
18-36
36-75
9-36
18-75
36-75
36-75
9-36
18-75
36-75
36-75
18-75
9-36
9-18
18-36
18-75
36-75
9-18
9-36
18-36
18-75
36-75
I
IN
➃
(mA/A)
35/1.27
35/0.63
35/0.31
35/1.56
35/0.76
35/0.38
35/1.81
35/0.89
35/0.46
35/2.48
35/1.23
35/0.61
50/1.2
38/0.6
35/0.6
35/0.58
50/1.22
35/0.6
45/0.73
45/0.7
38/0.71
145/1.5
90/2.92
55/1.44
45/0.72
30/0.7
110/2.92
50/1.42
70/1.44
45/0.72
35/0.7
Efficiency
Min.
Typ.
80%
81%
81%
81%
84%
82%
84%
85.5%
83.5%
85%
86%
86%
86.5%
87.5%
88.5%
87%
86%
87.5%
87.5%
87.5%
86%
85%
87%
88%
88%
90%
87%
86%
88%
88%
90%
82%
83%
83%
83%
86%
84%
85.5%
87%
85%
87%
88%
88%
88%
89.5%
91%
88.5%
87.5%
90%
89%
89%
87.5%
87.5%
89%
90%
90.5%
92%
89%
88%
90%
90.5%
92%
Alternate Trim
Configuration
Package
(Case,
Pinout)
C32, P51/52
C32, P51/52
C32, P51/52
C32, P51/52
C32, P51/52
C32, P51/52
C32, P51/52
C32, P51/52
C32, P51/52
C32, P51/52
C32, P51/52
C32, P51/52
C32, P51/52
C32, P51/52
C32, P51/52
C32, P51
C32, P51/52
C32, P51/52
C32, P51/52
C32, P51
C32, P51
C32, P51
C32, P51
C32, P51
C32, P51
C32, P51
C32, P51
C32, P51
C32, P51
C32, P51
C32, P51
➀
Typical at T
A
= +25°C under nominal line voltage and full-load conditions, unless noted.
➁
Ripple/Noise (R/N) is tested/specified over a 20MHz bandwidth. All models are specified with
an external 0.47µF multi-layer ceramic capacitor installed across their output pins.
➂
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
(with/without sense option) is varied from its nominal/midpoint value to either extreme.
➃
Nominal line voltage, no-load/full-load conditions.
U
HE
-
3.3
/
7500
-
D48
N
R
LX
T
Unipolar
High Efficiency
Nominal Output Voltage
Optional Functions
Input Voltage Range
Maximum Rated Output in mA
See page 13 for
complete Part
Number structure
& ordering details.
M E C H A N I C A L
S P E C I F I C A T I O N S
2.00
(50.80)
PLASTIC CASE
0.40
(10.16)
CASE C32
STANDOFF
0.020 (0.51)
I/O Connections
Pin
1
2
3
4
5
6
7
8
9
Function P51
+Input
–Input
No Pin
On/Off Control
No Pin
+Output
–Output
No Pin
Trim
Function P52
+Input
–Input
No Pin
On/Off Control
+Sense*
+ Output
–Output
–Sense*
Trim
0.20 MIN
(5.08)
0.040 ±0.001 DIA.
(1.016 ±0.025)
1.800
(45.72)
0.10
(2.54)
* Pins 5 and 8 are
installed for optional
R-suffix versions of
1.2-5V
OUT
models.
0.200
(5.08)
0.200
(5.08)
5
1
2
0.400
(10.16)
6
0.400
(10.16)
7
8
9
1.60
(40.64)
3
4
0.400 (10.16)
2 EQ. SP. @
0.200 (5.08)
0.100
(2.54)
BOTTOM VIEW
DIMENSIONS ARE IN INCHES (MM)
0.20
(5.08)
2
1 2 - 3 0 W, S I N G L E O U T P U T D C / D C C O N V E RT E R S
UHE Models
Performance/Functional Specifications
Typical @ T
A
= +25°C under nominal line voltage and full-load conditions, unless noted.
(1) (2)
Input
Input Voltage Range:
D12 Models (start up at 10V max.)
Q12 Models (start up at 10V max.)
D24 Models
Q48 Models
D48 Models
Overvoltage Shutdown:
D12 Models
Q12/D24 Models
D48/Q48 Models
Start-Up Threshold:
(2)
D12/Q12 Models
D24/Q48 Models
D48 Models
Undervoltage Shutdown:
D12/Q12 Models
D24/Q48 Models
D48 Models
(2)
Output
Overvoltage Protection:
1.2V Outputs
1.5V Outputs
1.8V Outputs
2.5V Outputs
3.3V Outputs
5V Outputs
12V Outputs
15V Outputs
Maximum Capacitive Loading:
(Low ESR capacitor)
Dynamic Load Response:
(50-100% load step to ±3% V
OUT
)
Start-Up Time:
(8)
V
IN
to V
OUT
and On/Off to V
OUT
Switching Frequency
MTBF
(9)
Operating Temperature
(Ambient):
Without Derating
With Derating
Thermal Shutdown
Storage Temperature
(10)
9-18 Volts (12V nominal)
9-36 Volts (24V nominal)
18-36 Volts (24V nominal)
18-75 Volts (48V nominal)
36-75 Volts (48V nominal)
18.5-23 Volts (20V typical)
37-42 Volts (39.5V typical)
NA
9.4-10 Volts (9.6V typical)
15.5-18 Volts (17V typical)
33.5-36 Volts (35V typical)
7.0-8.8 Volts (8V typical)
15-17 Volts (16.5V typical)
32-35.5 Volts (34.5V typical)
See Ordering Guide
5mA
Magnetic feedback
1.5-2.1 Volts
1.8-2.4 Volts
2.2-2.8 Volts
2.8 to 3.2 Volts
4 to 4.8 Volts
6.1-7.5 Volts
12.7-13.5 Volts
15.8-16.2 Volts
10,000µF (1.2-5V
OUT
)
2,000µF (12-15V
OUT
)
Dynamic Characteristics
200µsec maximum
(8)
4-8msec typical
15msec maximum
150-350kHz (model dependent)
Environmental
2.15 million hours
+55 to +65°C (model dependent)
To +100°C (see Derating Curves)
105 to +125°C
–50 to +125°C
Input Current:
Normal Operating Conditions
Standby Mode (Off, OV, UV)
Input Reflected Ripple Current
Input Filter Type
Reverse-Polarity Protection
Remote On/Off Control
(Pin 4):
(4)
Positive Logic (Standard)
(3)
10mAp-p
LC
Brief duration, 5A maximum
On = open, open collector, or
+3.5V-V
IN
applied. I
IN
= 2.6mA max.
Off = pulled low to 0-0.8V. I
IN
= 2mA max.
On = pulled low to 0-0.8V. I
IN
= 6mA max.
Off = open, open collector or
+3.5V to V
IN
applied. I
IN
= 1mA max.
Physical
Dimensions
Case Material
Pin Material
Weight:
1.6" x 2" x 0.40" (40.64 x 50.8 x 10.16mm)
Diallyl Phthalate
Brass, solder coated
1.51 ounces (46.9 grams)
Negative Logic ("N" Suffix Models)
Output
V
OUT
Accuracy
(50% load):
Initial
Temperatue Coefficient
Extreme
(5)
Ripple/Noise
(20MHz BW)
(1)
Line/Load Regulation
Efficiency
V
OUT
Trim Range
(6)
Primary to Secondary Insulation Level
Basic
All models are tested and specified with a single, external, 0.47µF, multi-layer ceramic output
capacitor and no external input capacitors, unless otherwise noted. All models will effectively
regulate under no-load conditions (with perhaps a slight increase in output ripple/noise).
(2)
See Technical Notes/Performance Curves for additional explanations and details.
(3)
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.
(4)
The On/Off Control is designed to be driven with open-collector (or equivalent) logic or the
application of appropriate voltages (referenced to –Input (pin 2)). Applying a voltage
to the On/Off Control pin when no input voltage is applied to the converter can cause permanent
damage. See Remote On/Off Control for more details.
(5)
Extreme Accuracy refers to the accuracy of either trimmed or untrimmed output voltages over all
normal operating ranges and combinations of input voltage, output load and temperature.
(6)
Tie the Output Trim pin (pin 9) to +Output (pin 6) for maximum trim down or to –Output (Output
Return/Common, pin 7) for maximum trim up. See Output Trimming for detailed trim equations.
(7)
The Current-Limit-Inception point is the output current level at which the converter's power-
limiting circuitry drops the output voltage 2% from its initial value. See Output Current Limiting
and Short-Circuit Protection for more details.
(8)
For Start-Up-Time specifications, output settling time is defined as the output voltage having
reached ±1% of its final value at maximum load current.
(9)
MTBF’s are calculated using TELCORDIA SR-332 Method 1 Case, ground fixed, +25°C ambient
air and full-load conditions. Contact DATEL for demonstrated life-test data.
(10)
All models are fully operational and meet all published specifications, including "cold start,"
at –40°C.
(1)
±1.5% maximum
±0.02% per °C
±3%
See Ordering Guide
See Ordering Guide
See Ordering Guide
±5% minimum (±10% for T models)
±5%
1500Vdc minimum (BASIC)
650pF
100MΩ
(7)
Minimum Loading for Specification:
(2)
No load
Remote Sense Compensation
(2)
Isolation Voltage:
Input-to-Output
Isolation Capacitance
Isolation Resistance
Current Limit Inception
(@98%V
OUT
):
10 Amp Models
7.5 Amp Models
5/6 Amp Models
2.5 Amp Models
2.0 Amp Models
Short Circuit Current (Hiccup)
12-15 Amps
8.2-11.5 Amps
6.5-8.5 Amps
2.6-3.75 Amps
2.1-3 Amps
1.5-2.3 Amps
3
XHE Series
1 2 - 3 0 W, S I N G L E O U T P U T D C / D C C O N V E RT E R S
Absolute Maximum Ratings
Input Voltage:
Continuous:
D12 Models
D24/Q12 Models
D48/Q48 Models
Transient (100msec):
D12 Models
D24/Q12 Models
D48/Q48 Models
On/Off Control (pin 4) Max. Voltages
Referenced to –Input (pin 2)
No Suffix
"N" Suffix
Input Reverse-Polarity Protection
Output Current
Subsequent re-start will not occur until the input is brought back up to the
Start-Up Threshold. This built in hysteresis prevents any unstable on/off
situations from occurring at a single input voltage.
All D12/Q12 models will start-up at 9.6V typically and will then work within
specifications from 9-18V or 9-36V respectively.
Start-Up Time
The V
IN
to V
OUT
Start-Up Time is the interval of time between the point at
which the ramping input voltage crosses the Start-Up Threshold 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/output capacitance, and load. The UHE Series implements a soft start
circuit that limits the duty cycle of its PWM controller at power up, thereby
limiting the input inrush current.
The On/Off Control to V
OUT
start-up time assumes the converter has its
nominal input voltage applied but is turned off via the On/Off Control pin. The
specification defines the interval between the point at which the converter
is turned on and the fully loaded output voltage enters and remains within
its specified accuracy band. Similar to the V
IN
to V
OUT
start-up, the On/Off
Control to V
OUT
start-up time is also governed by the internal soft start
circuitry and external load capacitance.
The difference in start up time from V
IN
to V
OUT
and from On/Off Control to
V
OUT
is therefore insignificant.
Input Overvoltage Shutdown
23 Volts
42 Volts
81 Volts
25½ Volts
50 Volts
100 Volts
+V
IN
+7 Volts
Current must be <5 Amps. Brief
duration only. Fusing recommended.
Current limited. Devices can
withstand sustained output short
circuits without damage.
+100°C
–50 to +125°C
+300°C
Case Temperature
Storage Temperature
Lead Temperature
(soldering, 10 sec.)
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.
T E C H N I C A L
N O T E S
Input Fusing
Certain applications and/or safety agencies may require the installation of
fuses at the inputs of power conversion components. Fuses should also be
used if the possibility of sustained, non-current-limited, input-voltage polarity
reversals exists. For DATEL UHE 12-30 Watt DC/DC Converters, you should
use slow-blow type fuses, installed in the ungrounded input supply line, with
values no greater than the following.
Model
Output/Input
1.2 V
OUT
1.5 V
OUT
1.8 V
OUT
2.5 V
OUT
3.3 V
OUT
5 V
OUT
12 V
OUT
15 V
OUT
D12
3
4
5
5
--
--
6
6
Fuse Values in Amps
Q12
D24
Q48
--
2
--
--
2
--
--
2.5
--
--
2.5
--
7.5
-
3
6
-
3
--
3
5
--
3
5
D48
1
1
1
1
1.5
2
2
2
All D12/Q12 and D24 Models of the UHE DC/DC converters are equipped
with Input Overvoltage Protection. Input voltages exceeding the input over-
voltage shutdown specification listed in the Performance/Functional Specifi-
cations will cause the device to shutdown. A built-in hysteresis for all models
will not allow the converter to restart until the input voltage is sufficiently
reduced.
All 48V
IN
models have this overvoltage shutdown function disabled because
of requirements for withstanding brief input surges to 100V for up to 100msec
without output voltage interruption.
Please contact DATEL to have input overvoltage shutdown for D48/Q48
models enabled.
Input Source Impedance
UHE converters must be driven from a low ac-impedance input source.
The DC/DC's performance and stability can be compromised by the use of
highly inductive source impedances. The input circuit shown in Figure 2 is a
practical solution that can be used to minimize the effects of inductance in
the input traces. For optimum performance, components should be mounted
close to the DC/DC converter. If the application has a high source imped-
ance, low V
IN
models can benefit of increased external input capacitance.
All relevant national and international safety standards and regulations must
be observed by the installer. For system safety agency approvals, the
converters must be installed in compliance with the requirements of the end-
use safety standard, e.g. IEC/EN/UL60950.
Input Undervoltage Shutdown and Start-Up Threshold
Under normal start-up conditions, devices will not begin to regulate until
the ramping-up input voltage exceeds the Start-Up Threshold Voltage (35V
for "D48" models). Once operating, devices will not turn off until the input
voltage drops below the Undervoltage Shutdown limit (34V for "D48" models).
4
1 2 - 3 0 W, S I N G L E O U T P U T D C / D C C O N V E RT E R S
UHE Models
I/O Filtering, Input Ripple Current, and Output Noise
All models in the UHE 12-30 Watt DC/DC Converters are tested/specified for
input reflected ripple current and output noise using the specified external
input/output components/circuits and layout as shown in the following two
figures.
External input capacitors (C
IN
in Figure 2) serve primarily as energy-storage
elements, minimizing line voltage variations caused by transient IR drops in
conductors from backplane to the DC/DC. Input caps should be selected
for bulk capacitance (at appropriate frequencies), low ESR, and high rms-
ripple-current ratings. The switching nature of DC/DC converters requires
that dc voltage sources have low ac impedance as highly inductive source
impedance can affect system stability. In Figure 2, C
BUS
and L
BUS
simulate
a typical dc voltage bus. Your specific system configuration may necessitate
additional considerations.
TO
OSCILLOSCOPE
CURRENT
PROBE
+SENSE
+OUTPUT
COPPER STRIP
C1
C2
SCOPE
R
LOAD
–OUTPUT
–SENSE
COPPER STRIP
C1 = 0.47µF CERAMIC
C2 = NA
LOAD 2-3 INCHES (51-76mm) FROM MODULE
Figure 3. Measuring Output Ripple/Noise (PARD)
Minimum Output Loading Requirements
+INPUT
+
L
BUS
C
BUS
C
IN
V
IN
–
UHE converters employ a synchronous-rectifier design topology and all
models regulate within spec and are stable under no-load to full load condi-
tions. Operation under no-load conditions however might slightly increase the
output ripple and noise.
Thermal Shutdown
–INPUT
C
IN
= 33µF, ESR < 700mΩ @ 100kHz
C
BUS
= 220µF, ESR < 100mΩ @ 100kHz
L
BUS
= 12µH
Figure 2. Measuring Input Ripple Current
These UHE converters are equipped with thermal-shutdown circuitry. If envi-
ronmental conditions cause the internal temperature of the DC/DC converter
to rise above the designed operating temperature, a precision temperature
sensor will power down the unit. When the internal temperature decreases
below the threshold of the temperature sensor, the unit will self start. See
Performance/Functional Specifications.
Output Overvoltage Protection
UHE output voltages are monitored for an overvoltage condition via magnetic
feedback. The signal is coupled to the primary side and if the output voltage
rises to a level which could be damaging to the load, the sensing circuitry
will power down the PWM controller causing the output voltages to decrease.
Following a time-out period the PWM will restart, causing the output voltages
to ramp to their appropriate values. If the fault condition persists, and the
output voltages again climb to excessive levels, the overvoltage circuitry will
initiate another shutdown cycle. This on/off cycling is referred to as "hiccup"
mode.
Contact DATEL for an optional output overvoltage monitor circuit using a
comparator which is optically coupled to the primary side thus allowing tighter
and more precise control.
Current Limiting
As soon as the output current increases to 10% to 50% above its rated value,
the DC/DC converter will go into a current-limiting mode. In this condition, the
output voltage will decrease proportionately with increases in output current,
thereby maintaining somewhat constant power dissipation. This is commonly
referred to as power limiting. Current limit inception is defined as the point
at which the full-power output voltage falls below the specified tolerance.
See Performance/Functional Specifications. If the load current, being drawn
from the converter, is significant enough, the unit will go into a short circuit
condition as specified under "Performance."
In critical applications, output ripple/noise (also referred to as periodic and
random deviations or PARD) may be reduced below specified limits using
filtering techniques, the simplest of which is the installation of additional
external output capacitors. These output caps function as true filter elements
and should be selected for bulk capacitance, low ESR and appropriate
frequency response. All external capacitors should have appropriate voltage
ratings and be located as close to the converter as possible. Temperature
variations for all relevant parameters should also be taken carefully into
consideration.
The most effective combination of external I/O capacitors will be a function
of line voltage and source impedance, as well as 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 Engineering
Group for additional details.
In Figure 3, the two copper strips simulate real-world pcb impedances
between the power supply and its load. In order to minimize measurement
errors, scope measurements should be made using BNC connectors, or the
probe ground should be less than ½ inch and soldered directly to the fixture.
Floating Outputs
Since these are isolated DC/DC converters, their outputs are "floating" with
respect to their input. Designers will normally use the –Output (pin 7) as the
ground/return of the load circuit. You can, however, use the +Output (pin 6) as
ground/return to effectively reverse the output polarity.
5
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