Datenblatt

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rev.
PART NUMBER: VPOL20A-12W-SMT
page
1 of 14
date
08/2007
DESCRIPTION: point of load converter
features
* industry standard pin out
* high efficiency to 94%
* 300 KHz switching frequency
* 6.0-14 VDC wide input range
* 0.75-5.0 VDC wide output range
* over temperature protection
* continuous short circuit protection
* remote on/off
* cost-efficient open frame design
* UL/C-UL60950 certified
* output voltage sequencing (tracking)
* power good signal
1. INTRODUCTION
2. VPOL20A-12W-SMT CONVERTER FEATURES
6. SAFETY
6.1 Input Fusing and Safety Considerations.
3. GENERAL DESCRIPTION
3.1 Electrical Description
7. APPLICATIONS
7.1 Layout Design Challenges.
3.2 Thermal Packaging and Physical Design.
7.2 Convection Requirements for Cooling
4. TECHNICAL SPECIFICATIONS
7.3 Thermal Considerations
5. MAIN FEATURES AND FUNCTIONS
5.1 Operating Temperature Range
7.4 Power De-Rating Curves
5.2 Over-Temperature Protection (OTP)
7.6 Input Capacitance at the Power Module
5.3 Output Voltage Adjustment
7.7 Test Set-Up
5.4 Safe Operating Area (SOA)
7.8 Remote Sense Compensation
5.5 Over Current Protection
7.9 VPOL20A-12W-SMT Series Output Voltage Adustment.
5.6 Remote ON/OFF
7.10 Output Ripple and Noise Measurement
5.7 UVLO (Under-Voltage Lockout)
7.11 Output Capacitance
5.8 Output Voltage Sequencing (Tracking)
7.12 VPOL20A-12W-SMT Reflow Profile
7.5 Efficiency vs Load Curves
8. MECHANICAL OUTLINE DIAGRAMS
20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2382
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rev.
PART NUMBER: VPOL20A-12W-SMT
1. Introduction
are highly efficient, reliable and compact, high power density, single
2 of 14
date
08/2007
DESCRIPTION: point of load converter
converter is also protected against over-temperature conditions. If the
converter is overloaded or the ambient temperature gets too high, the
converter will shut down to protect the unit.
This application note describes the features and functions of CUI INC's
VPOL20A-12W-SMT series of Non Isolated DC-DC Converters. These
page
L1
Q1
+VIN
output DC/DC converters. These “Point of Load” modules serve the
+VO
C1
needs specifically of the fixed and mobile telecommunications and
Q2
D1
C2
R sense
+SENSE
computing market, employing economical distributed Power
Architectures. VPOL20A-12W-SMT series provide precisely regulated
output voltage range from 0.7525V to 5.0Vdc over a wide range of input
COM
COM
voltage (Vi=6.0 – 14Vdc) and can operate over an ambient temperature
range of –40°C to +85°C. Ultra-high efficiency operation is achieved
through the use of synchronous rectification and drive control
techniques.
PGood
ON/OFF
PWM IC
ERR AMP
SEQ
R1
R trim
TRIM
R2
The modules are fully protected against short circuit and overtemperature conditions. CUI INC's world class automated
manufacturing methods, together with an extensive testing and
qualification program, ensure that all VPOL20A-12W-SMT series
Figure 1. Electrical Block Diagram
converters are extremely reliable.
3.2 Thermal Packaging and Physical Design.
2. VPOLW20A-12-SMT Converter Features
The VPOL20A-12W-SMT series uses a multi-layer FR4 PCB
High efficiency topology, typically 94% at 5.0Vdc
Industry standard footprint
Wide ambient temperature range, -40C to +85C
Cost efficient open frame design
Programmable output voltage via external resistor from 0.7525 to
5.0Vdc
No minimum load requirement (Stable at all loads)
Remote ON/OFF
Remote sense compensation
Fixed switching frequency
Continuous short-circuit protection and over current protection
Over-temperature protection (OTP)
Monotonic Startup with pre-bias at the output.
UL/IEC/EN60950 Certified.
Output Voltage Sequencing( Tracking )
Power Good Signal (Option)
construction. All surface mount power components are placed on one
side of the PCB, and all low-power control components are placed on
the other side. Thus, the Heat dissipation of the power components is
optimized, ensuring that control components are not thermally stressed.
The converter is an open-frame product and has no case or case pin.
The open-frame design has several advantages over encapsulated
closed devices. Among these advantages are:
Efficient Thermal Management: the heat is removed from the
heat generating components without heating more sensitive, small
signal control components.
Environmental: Lead free open-frame converters are more easily
re-cycled.
Cost Efficient: No encapsulation. Cost efficient open-frame
construction.
Reliable: Efficient cooling provided by open frame construction
offers high reliability and easy diagnostics .
3. General Description
3.1 Electrical Description
A block diagram of the VPOL20A-12W-SMT Series converter is shown
in Figure 1. Extremely high efficiency power conversion is achieved
through the use of synchronous rectification and drive techniques.
Essentially, the powerful VPOL20A-12W-SMT series topology is based
on a non-isolated synchronous buck converter. The control loop is
optimized for unconditional stability, fast transient response and a very
tight line and load regulation. In a typical pre-bias application the
VPOL20A-12W-SMT series converters do not draw any reverse current
at start-up. The output voltage can be adjusted from 0.7525 to 5.0vdc,
using the TRIM pin with a external resistor. The converter can be shut
down via a remote ON/OFF input that is referenced to ground. This
input is compatible with popular logic devices; a 'positive' logic input is
supplied as standard.
Positive logic implies that the converter is enabled if the remote
ON/OFF input is high (or floating), and disabled if it is low. The
20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2382
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rev.
page
3 of 14
date
08/2007
DESCRIPTION: point of load converter
PART NUMBER: VPOL20A-12W-SMT
4. Technical Specifications
(All specifications are typical at nominal input, full load at 25°C unless otherwise noted.)
PARAMETER
ABSOLUTE MAXIMUM RATINGS
Input Voltage
Continuous
Operating Temp erature
See Thermal Considerations Section
NOTES and CONDITIONS
Operating Input Voltage
Min.
Typical Max.
Units
ALL
0
16
Vdc
ALL
-40
+85
°C
ALL
-55
+125
°C
ALL
6.0
6.5
14
14
Vdc
Storage Temperature
INPUT CHARACTERISTICS
Device
Vo=4.5V
Vo=5.0V
Input Under-Voltage Lockout
Turn-On Voltage Threshold
Turn-Off Voltage Threshold
Lockout Hysteresis Voltage
ALL
ALL
ALL
ALL
12
12
5.0
4.0
1.0
Vdc
Vdc
Vdc
Maximum Input Current
Vin=0 to 14Vdc , Io=Io,max.
No-Load Input Current
Vo=0.7525V
Vo=1.2V
Vo=1.5V
Vo=1.8V
Vo=2.0V
Vo=2.5V
Vo=3.3V
Vo=5.0V
ALL
Off Converter Input Current
Shutdown input idle current
ALL
10
mA
ALL
0.4
As
2
Inrush Current (I t)
Input Reflected-Ripple Current
19
40
50
50
50
60
65
75
95
A
mA
2
P-P thru 1uH inductor, 5Hz to 20MHz
ALL
220
mA
Output Voltage S et Point
Vin=Nominal Vin , Io=Io.max, Tc=25°C
ALL
-1.5% Vo,set +1.5%
Vdc
Output Voltage Trim Adjustment Range
Selected by an e xternal resistor
ALL
0.7525
Vdc
OUTPUT CHARACTERISTIC
5.0
Output Voltage Regulation
Load Regulation
Io=Io.min to Io.max
ALL
-0.5
+0.5
%
Line Regulation
Vin=low line to high line
ALL
-0.2
+0.2
%
Tempera ture Coefficient
Ta=-40° C to 85°C
ALL
-0.03
+0.03
%/°C
Output Voltage Ripple and Noise
5Hz to 20MHz bandwidth
Peak-to-Peak
Full Load, 1uF ceramic and 10uF tantalum
ALL
75
mV
RMS
Full Load, 1uF ceramic and 10uF tantalum
ALL
30
mV
Lo w ESR
ALL
8000
uF
ALL
0
Output DC Current-Limit Inception
Output Voltage =90% Nominal Output Voltage
ALL
24
Shout Circuit Protection
Continuous with Hiccup Mode
Sequenc y Sle w Rate Capability
dVSEQ/dt
External Capacitive Load
Operating Output Current Range
0.1
Sequencing Delay Time
30
20
A
36
A
1.0
10
Tracking Accuracy
Power up
Power down
Power Good Signal
Asserted Logic High Vo
ALL
Suffix “P”
V/ms
ms
90
20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2382
200
400
mV
110
%
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rev.
page
4 of 14
date
08/2007
DESCRIPTION: point of load converter
PART NUMBER: VPOL20A-12W-SMT
Error Brand
50% Step Load Change, di/dt=2.5A/us
ALL
200
mV
Setting Time (within 1% Vout nominal)
50% Step Load Change, di/dt=2.5A/us
ALL
200
us
EFFICIENCY
100% Load
ISOLATION CHARACTERISTICS
Input to Output
Vo=0.7525V
Vo=1.2V
Vo=1.5V
Vo=1.8V
Vo=2.0V
Vo=2.5V
Vo=3.3V
Vo=5.0V
ALL
Non-isolation
ALL
78
84
87
88
89
90
92
94
%
0
Vdc
FEATURE CHARACTERISTICS
Switching Frequency
ON/OFF Control, Positive Logic Remote On/Off
Logic Low (Module Off)
Logic High (Module On)
ALL
or Open Circuit
ON/OFF Control, Negative Logic Remote On/Off
Logic Low (Module On)
or Open Circuit
Logic High (Module Off)
ON/OFF Current (for both remote on/off logic)
Leakage Current (for both remote on/off logic)
Turn-On Delay and Rise Time
Turn-On Delay Time, From On/Off Control
Turn-On Delay Time, From Input
Output Voltage Rise Time
Over Temperature Protection
GENERAL SPECIFICATIONS
MTBF
Weight
Dimensions
1.7x0.53
300
KHz
VPOLW20A-12-SMT
0
0.4
Vin
Vdc
Vdc
VPOL20A-12W-SMT
0
2.8
0.4
Vin
Vdc
Vdc
1
1
mA
mA
Ion/off at Von/off =0.0V
Logic High, Von/off=14V
ALL
ALL
Von/off to 10 %Vo,set
Vin,min. to 10%V o,set
10%Vo,set to 90 %Vo,set
ALL
ALL
ALL
ALL
3
3
4
130
ms
ms
ms
°C
ALL
0.9
M hours
ALL
11
grams
Io=100%of Io.max;Ta=2 5°C per MIL-HDBK217F
x0.366 inches(43.2x13.46x9.3 mm)
20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2382
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rev.
page
5 of 14
date
08/2007
DESCRIPTION: point of load converter
PART NUMBER: VPOL20A-12W-SMT
5. Main Features and Functions
removed. The power module will supply up to 150% of rated current. In
the event of an over current converter will go into a hiccup mode
5.1 Operating Temperature Range
protection.
CUI INC's VPOL20A-12W-SMT series converters highly efficient
5.6 Remote ON/OFF
converter design has resulted in its ability to operate over a wide ambient
temperature environment ( -40°C to 85°C). Due consideration must be
given to the de-rating curves when ascertaining maximum power that can
be drawn from the converter. The maximum power drawn is influenced
by a number of factors, such as:
The remote ON/OFF input feature of the converter allows external
circuitry to turn the converter ON or OFF. Active-high remote ON/OFF is
available as standard. The VPOL20A-12W-SMT is turned on if the
remote ON/OFF pin is high(=Vin), or left open. Setting the pin
low(<0.4Vdc) will turn the converter ‘Off’. The signal level of the remote
Input voltage range.
on/off input is defined with respect to ground. If not using the remote
Output load current.
Air velocity (forced or natural convection).
Mounting orientation of converter PCB with respect to the Airflow.
Motherboard PCB design, especially ground and power planes.
These can be effective heat sinks for the converter.
5.2 Over-Temperature Protection (OTP)
on/off pin, leave the pin open (module will be on). The part number suffix
“N” is Negative remote ON/OFF version. The unit is guaranteed OFF
over the full temperature range if this voltage level exceeds 2.8Vdc. The
converters are turned on If the on/off pin input is low (<0.4Vdc) or left
open. The recommended VPOL20A-12W-SMT remote on/off drive circuit
as shown as figure 3, 4.
The VPOL20A-12W-SMT Series converters are equipped with nonlatching over-temperature protection. A temperature sensor monitors the
+Vin
temperature of the hot spot (typically, top switch). If the temperature
exceeds a threshold of 130°C (typical) the converter will shut down,
disabling the output. When the temperature has decreased the converter
will automatically restart.
The over-temperature condition can be induced by a variety of reasons
ON/OFF
Control
Remote ON/OFF
Q1
VPOL20A-12W-SMT
such as external overload condition or a system fan failure.
Common
5.3 Output Voltage Adjustment
Section 7.8 describes in detail as to how to trim the output voltage with
respect to its set point. The output voltage on all models is trimmable in
+Vo
Common
Figure 3. Positive Remote ON/OFF Input Drive Circuit
the range 0.7525 – 5.0Vdc.
5.4 Safe Operating Area (SOA)
+Vin
Figure 2 provides a graphical representation of the Safe Operating Area
(SOA) of the converter. This representation assumes ambient operating
conditions such as airflow are met as per thermal guidelines provided in
Sections 7.2 and 7.3.
Vo
ON/OFF
Control
+Vo
VPOL20A-12W-SMT
Remote ON/OFF
Common
Common
Figure 4. Negative Remote ON/OFF Input Drive Circuit
Vo,nom
VOLTAGE (V)
Q1
Safe Operating Area
CURRENT (A)
Io,max Io,CL Io
Figure 2. Maximum Output Current Safe Operating Area
5.5 Over Current Protection
All different voltage models have a full continuous short-circuit protection.
The unit will auto recover once the short circuit is removed. To provide
protection in a fault condition, the unit is equipped with internal overcurrent protection. The unit operates normally once the fault condition is
20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2382
For more information, please visit the product page.
rev.
page
6 of 14
date
08/2007
DESCRIPTION: point of load converter
PART NUMBER: VPOL20A-12W-SMT
Power start up with SEQ signal
Input Voltage=12Vdc
Master DC/DC output voltage (CH1) = 5Vdc
Salve DC/DC output voltage (CH2)=3.3Vdc
Sequencing voltage= 0.67V/msec
5.7 UVLO (Under-Voltage Lockout)
The voltage on the Vcc pin determines the start of the operation of the
Converter. When the input Vcc rises and exceeds about 5.0V the
converter initiates a soft start. The UVLO function in the converter has a
hysteresis (about 1V) built in to provide noise immunity at start-up.
5.8 Output Voltage Sequencing (Tracking)
The VPOL20A-12W-SMT series includes a sequencing feature. It is able
implement various types of output voltage sequencing in customer
applications, VPOL20A-12W-SMT series is accomplishable through an
additional sequencing pin. When not using the sequencing feature, tie
the SEQ pin to +Vin. When the signal voltage is applied to the SEQ pin,
the output voltage tracks this voltage until the output reaches the set
point voltage. The SEQ voltage needs to be set higher than the set point
of the module. The output voltage will be follow by the voltage on the
SEQ pin. On the multiple modules application, we can connect SEQ pin
and input signal voltage together to apply on the SEQ pin. Customers
can get multiple modules to track their output voltages to follow the
voltage of the SEQ pin.
To control this module for sequen cing, when the input voltage
Figure 6. Example testing circuit of sequencing function
applied to the module. The on/off pin is left unconnected so that
the module is ON by default. After applying input voltage to the module, a
minimum of 10msec delay is required before applying voltage on the
SEQ pin and slew rate of the voltage on the SEQ pin see technical
Power turn off with SEQ signal voltage
Input Voltage=12Vdc (CH1)
Master DC/DC output voltage (CH2) = 5Vdc
Salve DC/DC output voltage (CH3)=3.3Vdc
specifications “ dVSEQ/dt “. After 10msec delay, an Analog voltage is
applied to the SEQ pin and the output voltage of the module will track
this voltage until output voltage reaches the set point voltage. To initiate
simultaneous shutdown of the modules, the SEQ pin voltage is lowered
in a controlled manner. Output voltage of the modules track the voltages
below their set-point voltage voltages. A valid input voltage must be
maintained until the tracking and output voltages reach ground potential
to ensure a controlled shutdown of the modules.
A typical example testing circuit used master DC/DC converter and
VPOL20A-12W-SMT Module as shown as below:
+Vin
Power
+
C1
+Vo
CH1
R1
Load
Master DC/DC Converter
Supply
Common
Common
Figure 7. Example testing circuit of sequencing function
+Vin
+Vo
SEQ
CH2
VPOL20A-12W-SMT
Common
C2
Common
Figure 5. Example testing circuit of sequencing function
CH3
R2
Load
6. Safety
6.1 Input Fusing and Safety Considerations.
Agency Approvals: The power Supply shall be submitted to and receive
formal approval from the following test agencies.
1.The power supply shall be approved by a nationally recognized testing
rd
laboratory to UL/CSA 60950 3 Edition (North America) and EN60950
(International)
20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2382
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rev.
PART NUMBER: VPOL20A-12W-SMT
page
7 of 14
date
08/2007
DESCRIPTION: point of load converter
2. CB Certificate from an internationally recognized test house in
accordance with EN 60950.
The VPOL20A-12W-SMT series converters do not have an internal fuse.
However, to achieve maximum safety and system protection, always
use an input line fuse. The safety agencies require a time-delay fuse
with a maximum rating of 25A.
7. Applications
7.1 Layout Design Challenges.
In optimizing thermal design the PCB is utilized as a heat sink. Also
some heat is transferred from the VPOL20A-12W-SMT module to the
main board through connecting pins. The system designer or the end
user must ensure that other components and metal in the vicinity of the
VPOL20A-12W-SMT series meet the spacing requirements to which the
system is approved.
Low resistance and low inductance PCB layout traces are the norm and
should be used where possible. Due consideration must also be given to
proper low impedance tracks between power module, input and output
grounds. The recommended VPOL20A-12W-SMT footprint as shown as
figure 8.
Recommended Pad Layout
Dimensions are in millimeters and(inches)
3.05
(0.120)
7.54
(0.297)
4.83
4.83
4.83
4.83
4.83
(0.190) (0.190) (0.190) (0.190) (0.190)
PGood +SENSE TRIM +VO
COM
SEQ
10.28
(0.405)
10.92
(0.430)
+VIN
ON/OFF
29.90
(1.177)
PAD SIZE
MIN:3.556x2.413(0.140x0.095)
MAX:4.19x2.79(0.165x0.110)
Figure 8. Recommended VPOL20A-12W-SMT Footprint
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rev.
page
8 of 14
date
08/2007
DESCRIPTION: point of load converter
PART NUMBER: VPOL20A-12W-SMT
7.2 Convection Requirements for Cooling
To predict the ap proximate cooling needed for the module, refer to the
Power De-rating curves in Figure 11. These de -rating curves are
approximations of the ambient temperatures and airflows required to
keep the power module temperature below its maximum rating. Once the
module is assembled in the actual system, the module’s temperature
should be checked as shown in Figure 9 to ensure it does not exceed
120°C.
Proper cooling can be verified by measuring the power module’s
temperature at “ Tref ” as shown in Figure 10.
Wind
Tunnel
25.4(1.0)
PWBs
Power Module
Figure 10. Temperature Measurement Location for VPOL20A-
12W-SMT
7.3 Thermal Considerations
The power module operates in a variety of thermal environments;
76.2(3.0)
however, sufficient cooling should be provided to help ensure reliable
operation of the unit. Heat is removed by conduction, convection, and
radiation to the surrounding environment. The thermal data presented is
Thermocuple Location
for measuring
ambient temperature
and airflow
12.7(0.5)
Air
flow
based on measurements taken in a set-up as shown in Figure10. Figure
11 represents the test data. Note that the airflow is parallel to the long
axis of the module as shown in Figure 7 for the VPOL20A-12W-SMT.
The temperature at “ Tref ” location should not exceed 120 °C. The
output power of the module should not exceed the rated power for the
module (VO, set x IO, max). The thermal data presented is based on
measurements taken in a wind tunnel. The test setup shown in Figure 7
and EUT need to solder on 53.8mm x 43.2mm (2.12'' x 1.7'') test pcb.
Note that airflow is parallel to the long axis of the module as shown in
Fig10.
Note : Dimensions are in millimeters and (inches)
Figure 9. Thermal Test Setup
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rev.
DESCRIPTION: point of load converter
PART NUMBER: VPOL20A-12W-SMT
TYPICAL POWER DERATING FOR 5 Vin 3.3 Vout
25.0
Output Current(A)
20.0
15.0
0LFM
100LFM
200LFM
300LFM
400LFM
10.0
5.0
0.0
0
10
20
30
40
50
60
70
80
90
100
Ambient Temperature(o C)
NOTE:
1. specific input & output derating curves available, please
contact CUI INC for detail
20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2382
page
9 of 14
date
08/2007
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rev.
page
10 of 14
date
08/2007
DESCRIPTION: point of load converter
PART NUMBER: VPOL20A-12W-SMT
7.5 Efficiency vs Load Curves
VPOL20A-12W-SMT Vo=5.0V (Eff Vs Io)
VPOL20A-12W-SMT Vo=3.3V (Eff Vs Io)
95%
95%
Efficincy (%)
100%
Efficincy (%)
100%
90%
90%
85%
85%
6.5V
12V
14V
80%
75%
6.0V
12V
14V
80%
75%
70%
70%
0
2
4
6
8
10
12
Current Load (A)
14
16
18
20
VPOL20A-12W-SMT Vo=2.5V (Eff Vs Io)
0
95%
95%
4
6
8
10
12
Current Load (A)
14
16
18
20
VPOL20A-12W-SMT Vo=2.0V (Eff Vs Io)
Efficincy (%)
100%
Efficincy (%)
100%
2
90%
90%
85%
85%
6.0V
12V
14V
80%
75%
6.0V
12V
14V
80%
75%
70%
70%
0
2
4
6
8
10
12
Current Load (A)
14
16
18
0
20
VPOL20A-12W-SMT Vo=1.8V (Eff Vs Io)
95%
95%
4
6
8
10
12
Current Load (A)
14
16
18
20
VPOL20A-12W-SMT Vo=1.5V (Eff Vs Io)
Efficincy (%)
100%
Efficincy (%)
100%
2
90%
90%
85%
85%
6.0V
12V
14V
80%
75%
6.0V
12V
14V
80%
75%
70%
70%
0
2
4
6
8
10
12
Current Load (A)
14
16
18
20
0
2
4
6
8
10
12
Current Load (A)
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14
16
18
20
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rev.
11 of 14
date
08/2007
DESCRIPTION: point of load converter
PART NUMBER: VPOL20A-12W-SMT
VPOLW 20A-12-SMT Vo=1.2V (Eff Vs Io)
100%
page
95%
90%
90%
Efficincy (%)
95%
Efficincy (%)
VPOL20A-12W-SMT Vo=0.75V (Eff Vs Io)
100%
85%
85%
80%
80%
75%
65%
60%
0
2
4
6
8
10
12
Current Load (A)
14
16
18
6.0V
12V
14V
75%
6.0V
12V
14V
70%
70%
65%
60%
20
0
2
4
6
8
10
12
Current Load (A)
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14
16
18
20
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rev.
page
12 of 14
date
08/2007
DESCRIPTION: point of load converter
PART NUMBER: VPOL20A-12W-SMT
Line.reg =
7.6 Input Capacitance at the Power Module
VHL _ VLL
x100 %
VLL
Where: VHL is the output voltage of maximum input voltage at full load.
The VPOL20A-12W-SMT converters must be connected to a low AC
VLL is the output voltage of minimum input voltage at full load.
source impedance. To avoid probl ems with loop stability source
inductance should be low. Also, the input capacitors should be placed
Current Meter
close to the converter input pins to de-couple distribution inductance.
A
However, the external input capacitors are chosen for suitable ripple
handling capability. Low ESR polymers are a good choice. They have
Power
high capacitance, high ripple rating and low ESR (typical <100mohm).
Supply
Electrolytic capacitors should be avoided. Circuit as shown in Figure 12
+Vin
A
+Vo
+Sense
+
V 100uF
Voltage Meter
VPOL20A-12W-SMT
represents typical measurement methods for ripple current. Input
Common
V
Load
Common
reflected-ripple current is measured with a simulated source Inductance
of 1uH. Current is measured at the input of the module.
Figure 13. VPOL20A-12W-SMT Series Test Setup
7.8 Remote Sense Compensation
To Oscilloscope
L1
+Vin
1uH
Power
+
2*100uF
Tantalum
Supply
Remote Sense regulates the output voltage at the point of load. It
+Vo
minimizes the effects of distribution losses such as drops across the
R1
VPOL20A-12W-SMT
C2
1000uF Electronlyic
ESR<0.1ohm
Com
Load
Com
Figure 12. Input Reflected-Ripple Test Setup
7.7 Test Set-Up
The basic test set-up to measure parameters such as efficiency and
load regulation is shown in Figure 13. Things to note are that this
converter is non-isolated, as such the input and output share a common
ground. These grounds should be connected together via low
connecting pin and PCB tracks (see Figure 17). Please note however,
the maximum drop from the output pin to the point of load should not
exceed 500mV for remote compensation to work.
The amount of power delivered by the module is defined as the output
voltage multiplied by the output current (VO x IO).
When using TRIM UP, the output voltage of the module will increase
which, if the same output current is maintained, increases the power
output by the module. Make sure that the maximum output power of the
module remains at or below the maximum rated power.
When the Remote Sense feature is not being used, leave sense pin
disconnected.
Figure 14. Circuit Configuration for Remote Sense Operation
impedance ground plane in the application circuit. When testing a
converter on a bench set-up, ensure that -Vin and -Vo are connected
together via a low impedance short to ensure proper efficiency and load
regulation measurements are being made. When testing the CUI INC's
VPOL20A-12W-SMT series under any transient conditions please
ensure that the transient response of the source is sufficient to power
the equipment under test. We can calculate the
Efficiency
Distribution Losses
+Vin
+Vo
+Sense
Load regulation and line regulation.
The value of efficiency is defined as:
Vo x Io
x100 %
ç=
Vin x Iin
Where:
Vo is output voltage,
VPOL20A-12W-SMT
Common
Common
R-Load
Distribution Losses
Io is output current,
Vin is input voltage,
Iin is input current.
The value of load regulation is defined as:
Load .reg =
VFL _ VNL
x100%
VNL
Where:
VFL is the output voltage at full load
VNL is the output voltage at no load
The value of line regulation is defined as:
20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2382
For more information, please visit the product page.
rev.
page
13 of 14
date
08/2007
DESCRIPTION: point of load converter
PART NUMBER: VPOL20A-12W-SMT
7.9 VPOL20A-12W-SMT Series Output Voltage
Adustment.
The output Voltage of the VPOL20A-12W-SMT can be adjusted in the
range 0.7525V to 5.0V by connecting a single resistor on the
motherboard (shown as Rtrim) in Figure 15. When Trim resistor is not
VO
COPPER STRIPS
10uF
Power
C1
SCOPE
1uF
LOAD
COM
Supply +
VIN
connected the output voltage defaults to 0.7525V
VPOL20A-12W-SMT
+Vo
Figure 16. Output Voltage Ripple and Noise Measurement Set-Up
7.11 Output Capacitance
Trim
R-Load
VPOL20A-12W-SMT
R trim-up
Common
Figure 15. Trim-up Voltage Setup
Rtrim-up
Output capacitors with its associated ESR values have an impact on
loop stability and bandwidth. CUI INC's converters are designed to
work with load capacitance up-to 8,000uF. It is reco mmended that any
10500 _
1000 )
_
Vo 0.7525
is the external resistor in ohm,
Vo is the desired output voltage
To give an exa mple of the above calculation, to set a voltage of 3.3Vdc,
Rtrim is given by:
10500
_ 1000 )
Rtrim = (
_
3.3 0.7525
Rtrim = 3.122K ohm
additional capacitance, typically 1,000uF and low ESR (<20mohm), be
connected close to the point of load and outside the remote
compensation point.
7.12 VPOL20A-12W-SMT Reflow Profile
An example of the VPOL20A-12W-SMT reflow profile is given in Fig 17.
Equipment used: SMD HOT AIR REFLOW HD-350SAR
Alloy: AMQ-M293TA or N C-SMQ92 IND-82088 SN63
REFLOW PROFILE
240
200
For various output values various resistors are calculated and provided
in Table 3 for co nvenience.
Vo,set (V)
0.7525
1.2
1.5
1.8
2.0
2.5
3.3
5.0
low ESR output capacitors should be located close to the point of load.
considerations for low resistance and low inductance tracks.
The value of Rtrim-up defined as:
Where:
stability with or without external capacitors. For good transient response
For high current applications point has already been made in layout
Common
Rtrim = (
CUI INC's VPOL20A-12W-SMT series converters provide unconditional
Rtrim (Kohm)
Open
22.46
13.05
9.024
7.417
5.009
3.122
1.472
TEMPERATURE (C)
+Vin
160
120
80
40
0
0
30
60
90
120 150 180 210 240
TIME (SECONDS)
Figure 17 VPOL20A-12W-SMT Reflow Profile
Table 3 – Trim Resistor Values
7.10 Output Ripple and Noise Measurement
The test set-up for noise and ripple measurements is shown in Figure
19. a coaxial cable with a 50ohm termination was used to prevent
impedance mismatch reflections disturbing the noise readings at higher
frequencies. The Output Ripple & Noise is measured with 1uf ceramic
and 10uf tantalum. The measured position are 50mm to 75mm(2” to 3”)
from the module. The “C1” is 200uF Tant alum capacitor ESR< 25m
20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2382
For more information, please visit the product page.
rev.
PART NUMBER: VPOL20A-12W-SMT
DESCRIPTION: point of load converter
20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2382
page
14 of 14
date
08/2007
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