User's Guide
SNVA082B – March 2004 – Revised May 2013
AN-1314 LM5020 Evaluation Board
1
Introduction
The LM5020 evaluation board is designed to provide the design engineer with a fully functional nonisolated flyback power converter to evaluate the LM5020 controller.
The performance of the evaluation board is as follows:
• Input range: 30V to 75V (100V peak)
• Output voltage: 3.3V
• Output current: 0.2 to 4.5A
• Measured efficiency: 85% at 1.5A, 83% at 4.5A
• Board size: 1.25 × 2.5 × 0.5 inches
• Load Regulation: 1.5%
• Line Regulation: 0.1%
• Line UVLO, Current Limit
The printed circuit board consists of 2 layers of 2 ounce copper on FR4 material with a total thickness of
0.050 inches. Soldermask has been omitted from some areas to facilitate cooling. The unit is designed for
continuous operation at rated load at < 40°C with normal convection cooling.
2
Theory of Operation
The flyback converter is an inductive based converter in which inductive energy is stored by applying a
voltage across an inductor in a similar manner to that of a boost converter. Here the similarity ends. A
second coupled winding of the inductor transfers the energy to a secondary side rectifier after the voltage
has been removed from the first winding. This allows the converter input and output grounds to be
configured either isolated or non-isolated. There is also a voltage/current ratio change possible by altering
the winding ratio between the first winding and the second winding. A semi-regulated auxiliary winding can
also be provided.
The flyback transformer is actually a coupled inductor with multiple windings wound on a single core. For
simplification, we will refer to the first, driven winding, as the primary and the main output winding as the
secondary winding of the flyback transformer.
The transformer’s primary inductance is typically made as large as is practical. However, the airgap
necessary to store the cycle energy lowers the obtainable inductance. The higher the primary inductance,
the less input ripple current will be generated and the less input filtering will be required.
As shown, the LM5020 directly drives a MOSFET switch to apply voltage across the primary. When the
switch turns off, the secondary applies a forward current to the output rectifier and charges the output
capacitor. In applications where the input voltage is considerably higher than the output voltage, the turns
ratio between primary and secondary will reflect the input/output voltage ratio and the duty cycle.
The LM5020 is a full-featured controller providing an internal start-up regulator, soft start, over-current and
under-voltage lockout.
All trademarks are the property of their respective owners.
SNVA082B – March 2004 – Revised May 2013
Submit Documentation Feedback
AN-1314 LM5020 Evaluation Board
Copyright © 2004–2013, Texas Instruments Incorporated
1
Powering and Loading Considerations
www.ti.com
30V - 75V
V+
VOUT
VCC
VIN
RT
UVLO
SS
LM5020
OUT
COMP
CS
FB
COMPENSATION
Simplified Flyback Converter
Figure 1. Simplified Flyback Converter
3
Powering and Loading Considerations
When applying power to the LM5020 evaluation board certain precautions should be followed. The
LM5020 evaluation board is quite forgiving of load and input power variations. The possibility of shipping
damage or infant failure is always a concern at first power-up.
4
Proper Connections
Be sure to choose the correct wire size when attaching the source supply and the load. Monitor the
current into and out of the UUT. Monitor the voltages in and out directly at the terminals of the UUT. The
voltage drop across the connecting wires will yield inaccurate measurements. For accurate efficiency
measurements, these precautions are especially important.
5
Source Power
At low input line voltage (30V) the input current will be approximately 0.63A, while at high input line
voltage the input current will be approximately 0.23. Therefore to fully test the LM5020 evaluation board a
DC power supply capable of at least 75V and 1A is required. The power supply must have adjustments for
both voltage and current. An accurate readout of output current is desirable since the current is not subject
to loss in the cables as voltage is.
The power supply and cabling must present a low impedance to the UUT. Insufficient cabling or a high
impedance power supply will cause droop during power supply application with the UUT inrush current. If
large enough, this droop will cause a chattering condition upon power up. This chattering condition is an
interaction with the UUT undervoltage lockout, the cabling impedance and the inrush current.
6
Loading
An appropriate electronic load specified for operation down to 2.0V is desirable. The maximum load
current is specified as 4.5A. Minimum load is specified at 5% or 0.23A. The resistance of a maximum load
is 0.73Ω (including cables). The resistance of a minimum load is 14.4Ω.
2
AN-1314 LM5020 Evaluation Board
SNVA082B – March 2004 – Revised May 2013
Submit Documentation Feedback
Copyright © 2004–2013, Texas Instruments Incorporated
Powering Up
www.ti.com
7
Powering Up
Using the shutdown feature provided on the UUT will allow powering up the source supply initially with a
low current level. It is suggested that the load be kept reasonably low during the first power up. Set the
current limit of the source supply to provide about 1½ times the wattage of the load. As you remove the
connection from the shutdown pin to ground, immediately check for 3.3 volts at the output. If more than a
couple of seconds pass without seeing an output voltage, remove input power.
A quick efficiency check is the best way to confirm that the UUT is operating properly. If something is
amiss you can be reasonably sure that it will affect the efficiency adversely. Few parameters can be
incorrect in a switching power supply without creating additional losses and potentially damaging heat. An
efficiency above 80% is expected.
After the unit is verified operationally, it can be powered up without use of the shutdown pin.
8
Typical Evaluation Setup
Scope
Volt-meter
+
75 Volt, 1 Amp
Power Supply
Evaluation Board
+
IN
Volt-meter
ON/OFF
(SHUTDOWN)
Current-meter
+
OUT
Electronic Load
-
Current
Meter
Jumper or single-pole switch
Figure 2. Typical Evaluation Setup
9
Performance Characteristics
9.1
Turn-on Waveforms
When applying power to the LM5020 evaluation board a certain sequence of events must occur. The softstart feature allows for a minimal output voltage for a short time until the feedback loop can stabilize
without overshoot. Figure 3, Figure 4, and Figure 5 show typical turn-on waveforms at no load, 5% load,
and at full load. Input voltage, output voltage and output current are shown.
Figure 6 shows the initial ramp-up of the Vcc pin to 7.7 volts through the internal regulator. The auxiliary
winding starts to supply a higher voltage as the output voltage rises. The resulting second ramp is shown
following the soft-start delay. This sequence is nearly identical for all loads and input voltages.
Trace 1: Input Voltage, at 30VDC. Volts/div = 20.0V Trace 2:
Output Voltage, no load. Volts/div = 2.0V Trace 3: Output
Current, no load. Amps/div = 100mA Horizontal Resolution =
1.0ms/div
Figure 3. Typical Turn-on Waveforms at No Load
Trace 1: Input Voltage, at 30VDC. Volts/div = 20.0V Trace 2:
Output Voltage, at 5% load. Volts/div = 2.0V Trace 3: Output
Current, at 5% load. Amps/div = 100mA Horizontal
Resolution = 1.0ms/div
Figure 4. Typical Turn-on Waveforms at 5% Load
SNVA082B – March 2004 – Revised May 2013
Submit Documentation Feedback
AN-1314 LM5020 Evaluation Board
Copyright © 2004–2013, Texas Instruments Incorporated
3
Performance Characteristics
www.ti.com
Trace 1: Input Voltage, at 30VDC. Volts/div = 20.0V Trace 2:
Output Voltage, at full load. Volts/div = 2.0V Trace 3: Output
Current, at full load. Amps/div = 2.0A Horizontal Resolution
= 1.0ms/div
Figure 5. Typical Turn-on Waveforms at Full Load
9.2
Trace 1: VCC pin with VIN = 30VDC, Load = 4.5A Volts/div
= 5.0V Trace 2: VIN approaching 30VDC Volts/div = 20.0V
Horizontal Resolution = 2.0ms/div
Figure 6. Initial Ramp-up of the Vcc Pin to 7.7V
Through the Internal Regulator
Load Step Response
Figure 7 shows the load step response at Vin = 30VDC for an instantaneous load change from 5% to full
load. The input voltage, output voltage and output current are shown.
9.3
Ripple Voltage and Ripple Current
Figure 8 shows the output ripple voltage, the output ripple current and the input ripple current relative to
the LM5020 gate drive.
Trace 1: Input Voltage, at 30VDC Volts/div = 20.0V Trace 2:
Output Voltage, at 3.3VDC Volts/div = 2.0V Trace 3: Load
changing from 0.23A to 4.5A instantaneously Amps/div =
2.0A Horizontal Resolution = 1.0ms/div
Figure 7. Load Step Response at Vin = 30VDC for an
Instantaneous Load Change from 5% to Full Load
4
Trace 1: Q1 gate drive at Vin = 48VDC Volts/div = 20.0V
Trace 2: Output ripple voltage Volts/div = 100mV Trace 3:
Output ripple current Amps/div = 20.0mA Trace 4: Input
ripple current Amps/div = 100mA Horizontal Resolution =
2.0µs/div
Figure 8. Output Ripple Voltage, Output Ripple
Current, and Input Ripple Current
AN-1314 LM5020 Evaluation Board
SNVA082B – March 2004 – Revised May 2013
Submit Documentation Feedback
Copyright © 2004–2013, Texas Instruments Incorporated
Performance Characteristics
www.ti.com
9.4
Transformer Waveforms
Figure 9, Figure 10, and Figure 11 show typical waveforms at the junction of Q1 MOSFET and the
transformer primary winding. Also shown are typical waveforms at the junction of the transformer
secondary and the output rectifier, D3. Figure 9 reflects an input voltage of 30VDC and a load of 4.5A.
Figure 10 reflects an input voltage of 50VDC with the same load. Figure 11 reflects an input voltage of
75VDC, also at full load.
Trace 1: Drain of Q1 at Vin = 30VDC; Volts/div = 50.0V
Trace 2: Anode of D3; Volts/div = 10.0V
Horizontal Resolution = 0.5µs/div
Figure 9. Typical Waveforms
Trace 1: Drain of Q1 at Vin = 50VDC; Volts/div = 50.0V
Trace 2: Anode of D3; Volts/div = 10.0V
Horizontal Resolution = 0.5µs/div
Figure 10. Typical Waveforms
Trace 1: Drain of Q1 at Vin = 75VDC; Volts/div = 50.0V
Trace 2: Anode of D3; Volts/div = 10.0V
Horizontal Resolution = 0.5µs/div
Figure 11. Typical Waveforms
SNVA082B – March 2004 – Revised May 2013
Submit Documentation Feedback
AN-1314 LM5020 Evaluation Board
Copyright © 2004–2013, Texas Instruments Incorporated
5
Bill of Materials
10
www.ti.com
Bill of Materials
The Bill of Materials is listed in Table 1 and includes the manufacturer and part number.
Table 1. Bill of Materials
Designator
6
Description
Manufacturer
Part Number
C1
2.2µF, 100V, CER, X7R, 1812
TDK
C4532X7R2A225M
C2
2.2µF, 100V, CER, X7R, 1812
TDK
C4532X7R2A225M
C3
0.01µF, 50V, CER, X7R, 0805
TDK
C2012X7R1H103K
C4
0.1µF, 100V, CER, X7R, 1206
TDK
C3216X7R2A104K
C5
0.01µF, 50V, CER, X7R, 0805
TDK
C2012X7R1H103K
C6
220pF, 50V, CER, COG, 0805
TDK
C2012COG1H221J
C7
3300pF, 50V, CER, COG, 0805
TDK
C2012COG1H332K
C8
100pF, 50V, CER, COG, 0805
TDK
C2012COG1H101J
C9
0.1µF, 50V, CER, X7R, 0805
TDK
C2012X7R1H104K
C10
4.7µF, 16V, CER, X7R, 1206
TDK
C3216X7R1C475K
C11
1000pF, 50V, CER, COG, 0805
TDK
C2012COG1H102J
C12
470pF, 50V, CER, COG, 0805
TDK
C2012COG1H471J
C13
100µF, 4V, CER, X7S, 1812
TDK
C4532X7S0G107M
C14
100µF, 4V, CER, X7S, 1812
TDK
C4532X7S0G107M
C15
270µF, 4V, ALUM ORG, 3018 PKG
KEMET
A700X277M0004AT
D1
DUAL, SIGNAL, COM CATH, SOT-23
CENTRAL SEMICONDUCTOR
CMPD2838E-NSA
D2
DUAL, SIGNAL, COM CATH, SOT-23
CENTRAL SEMICONDUCTOR
CMPD2838E-NSA
D3
SCHOTTKY RECT, 8A, 35V, D2PAK
ON SEMICONDUCTOR
J1
TERMINAL BLOCK, SCREW, 2 POS
PHOENIX CONTACT
MKDS ½-3.81
J2
TERMINAL BLOCK, SCREW, 2 POS
PHOENIX CONTACT
MKDS ½-3.81
Q1
MOSFET, N-CH, 150V, 85mΩ, PWR SO8
R1
10.0Ω, 1%, THICK FILM, 1206
VISHAY
CRCW120610R0J
R2
61.9K, 1%, THICK FILM, 1206
VISHAY
CRCW12066192F
R3
2.87K, 1%, THICK FILM, 0805
VISHAY
CRCW08052871F
R4
1.00K, 1%, THICK FILM, 0805
VISHAY
CRCW08051001F
R5
15.0K, 1%, THICK FILM, 0805
VISHAY
CRCW08051502F
R6
12.4K, 1%, THICK FILM, 0805
VISHAY
CRCW08051242F
R7
100Ω, 1%, THICK FILM, 0805
VISHAY
CRCW08051000F
R8
0.47Ω, 1%, THICK FILM, 1206
VISHAY
CRCW12060R47F
R9
0.47Ω, 1%, THICK FILM, 1206
VISHAY
CRCW12060R47F
R10
10.0Ω, 1%, 1W, THICK FILM, 2512
VISHAY
CRCW251210R0J
R11
2.43K, 1%, THICK FILM, 0805
VISHAY
CRCW08052431F
R12
1.47K, 1%, THICK FILM, 0805
VISHAY
CRCW08051471F
R13
20.0Ω, 1%, THICK FILM, 0805
VISHAY
CRCW080520R0F
SD
TERMINAL, SMALL TEST POINT
KEYSTONE
5002
SYNC
TERMINAL, SMALL TEST POINT
KEYSTONE
5002
T1
TRANSFORMER, FLYBACK, EFD20
COILCRAFT
B0695-A
OR T1
TRANSFORMER, FLYBACK, EFD20
PULSE
PA0751
VISHAY/SILICONIX
MBRD835L
Si7898DP
U1
CONTROLLER, SINGLE OUT, PWM, VSSOP-10
TEXAS INSTRUMENTS
LM5020
Z1
ZENER, 30V, SMB PKG.
ON SEMICONDUCTOR
1SMB5936B
AN-1314 LM5020 Evaluation Board
SNVA082B – March 2004 – Revised May 2013
Submit Documentation Feedback
Copyright © 2004–2013, Texas Instruments Incorporated
PCB Layouts
www.ti.com
11
PCB Layouts
The layers of the printed circuit board are shown in top down order. View is from the top down. Scale is
approximately X2.0. The printed circuit board consists of 2 layers of 2 ounce copper on FR4 material with
a total thickness of 0.050 inches.
SNVA082B – March 2004 – Revised May 2013
Submit Documentation Feedback
AN-1314 LM5020 Evaluation Board
Copyright © 2004–2013, Texas Instruments Incorporated
7
PCB Layouts
8
www.ti.com
AN-1314 LM5020 Evaluation Board
SNVA082B – March 2004 – Revised May 2013
Submit Documentation Feedback
Copyright © 2004–2013, Texas Instruments Incorporated
PCB Layouts
www.ti.com
SNVA082B – March 2004 – Revised May 2013
Submit Documentation Feedback
AN-1314 LM5020 Evaluation Board
Copyright © 2004–2013, Texas Instruments Incorporated
9
Application Circuit
12
www.ti.com
Application Circuit
C9
R10
R13
T1
V+
J1
30-75V IN
1
J2
+3.3V
2
C12
470 pF
D2
CMPD2838E
20
0.1 PF
10, 1W
1
C13
100 PF
GND
D3
MBRD835L
2
GND
R2
61.9k
R1
10
C4
0.1 PF
SD
R3
2.87k
GND
C10
4.7 PF
1
7
GND
VIN
VCC
UVLO
3
9
C6
220 pF
R5
15.0k
10
C8
100 pF
R6
12.4k
COMP
RT
CS
VFB
SS
GND
GND
Q1
Si7898DP
R11
2.43k
4
5
R12
1.47k
R7
8
2
100
6
R8
0.47
R9
0.47
GND
C11
1000 pF
LM5020
C5
0.01 PF
C7
3300 pF
D1
CMPD2838E
GND GND
U1
R4
1.00k
OUT
SYNC
GND
GND
GND
C3
0.01 PF
GND
Z1
GND
1SMB5936B
5
6
7
8
GND
C2
2.2 PF
OUT RTN
4
3
2
1
C1
2.2 PF
C15
270 PF
GND
GND
GND
C14
100 PF
GND
GND
GND
GND
Figure 12. Application Circuit: Input 36V to 78V, Output 3.3V, 4.5A
10
AN-1314 LM5020 Evaluation Board
SNVA082B – March 2004 – Revised May 2013
Submit Documentation Feedback
Copyright © 2004–2013, Texas Instruments Incorporated
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other
changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest
issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and
complete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale
supplied at the time of order acknowledgment.
TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms
and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary
to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily
performed.
TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products and
applications using TI components. To minimize the risks associated with Buyers’ products and applications, Buyers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or
other intellectual property right relating to any combination, machine, or process in which TI components or services are used. Information
published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or
endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the
third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration
and is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altered
documentation. Information of third parties may be subject to additional restrictions.
Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service
voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice.
TI is not responsible or liable for any such statements.
Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements
concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support
that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which
anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause
harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use
of any TI components in safety-critical applications.
In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI’s goal is to
help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and
requirements. Nonetheless, such components are subject to these terms.
No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties
have executed a special agreement specifically governing such use.
Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use in
military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components
which have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and
regulatory requirements in connection with such use.
TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of
non-designated products, TI will not be responsible for any failure to meet ISO/TS16949.
Products
Applications
Audio
www.ti.com/audio
Automotive and Transportation
www.ti.com/automotive
Amplifiers
amplifier.ti.com
Communications and Telecom
www.ti.com/communications
Data Converters
dataconverter.ti.com
Computers and Peripherals
www.ti.com/computers
DLP® Products
www.dlp.com
Consumer Electronics
www.ti.com/consumer-apps
DSP
dsp.ti.com
Energy and Lighting
www.ti.com/energy
Clocks and Timers
www.ti.com/clocks
Industrial
www.ti.com/industrial
Interface
interface.ti.com
Medical
www.ti.com/medical
Logic
logic.ti.com
Security
www.ti.com/security
Power Mgmt
power.ti.com
Space, Avionics and Defense
www.ti.com/space-avionics-defense
Microcontrollers
microcontroller.ti.com
Video and Imaging
www.ti.com/video
RFID
www.ti-rfid.com
OMAP Applications Processors
www.ti.com/omap
TI E2E Community
e2e.ti.com
Wireless Connectivity
www.ti.com/wirelessconnectivity
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2013, Texas Instruments Incorporated