Texas Instruments LM5168FEVM User manual
User’s Guide
LM5168FEVM EVM User's Guide
ABSTRACT
The LM5168FEVM is a 115-V DC/DC fly-buck regulator that employs synchronous rectification to achieve high
conversion efficiency in a small footprint. The EVM operates over a wide input voltage range of 20 V to 115
V (120-V absolute maximum) to provide a regulated 10-V output at up to 0.25 A with a 750-kHz switching
frequency. An additional 10-V floating output is provided through the fly-buck topology. The output voltage has
better than 1.5% set-point accuracy and is adjustable using an external resistor divider. The module design
uses the LM5168F-Q1 synchronous buck converter with wide input voltage range, wide duty-cycle range,
integrated high-side and low-side power MOSFETs, advanced overcurrent protection, and precision enable. With
AEC-Q100 grade 1 automotive qualification, the LM5168F-Q1 is rated to operate over a junction temperature
range of –40°C to +150°C.
Table 1-1. EVM Configuration
EVM CONVERTER IC PACKAGE
LM5168FEVM LM5168F-Q1 8-pin SO package with PowerPAD (4.89 mm × 3.90 mm)
Table of Contents
1 General TI High Voltage Evaluation User Safety Guidelines.............................................................................................. 3
2 EVM Characteristics............................................................................................................................................................... 5
3 LM5168FEVM Evaluation Module..........................................................................................................................................6
3.1 Quick Start Procedure........................................................................................................................................................6
3.2 Detailed Descriptions......................................................................................................................................................... 7
4 Schematic................................................................................................................................................................................8
5 PCB Layout..............................................................................................................................................................................9
6 Bill of Materials......................................................................................................................................................................11
7 Performance Curves.............................................................................................................................................................13
List of Figures
Figure 3-1. LM5168FEVM Top View............................................................................................................................................6
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Figure 4-1. LM5168FEVM Schematic..........................................................................................................................................8
Figure 5-1. Top Layer...................................................................................................................................................................9
Figure 5-2. Mid-Layer 1 Ground Plane........................................................................................................................................ 9
Figure 5-3. Mid-Layer 2 Routing................................................................................................................................................ 10
Figure 5-4. Bottom Layer........................................................................................................................................................... 10
Figure 7-1. Efficiency................................................................................................................................................................. 13
Figure 7-2. Load Regulation...................................................................................................................................................... 13
Figure 7-3. Load Regulation...................................................................................................................................................... 13
Figure 7-4. Typical Switching Waveform....................................................................................................................................13
Figure 7-5. Typical Start-Up Waveform......................................................................................................................................13
Figure 7-6. Typical Shutdown Waveform...................................................................................................................................13
List of Tables
Table 1-1. EVM Configuration......................................................................................................................................................1
Table 2-1. LM5168FQEVM Electrical Performance Characteristics............................................................................................ 5
Table 6-1. LM5168FEVM Bill of Materials ................................................................................................................................. 11
Trademarks
PowerPAD™ is a trademark of Texas Instruments.
All trademarks are the property of their respective owners.
Trademarks www.ti.com
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1 General TI High Voltage Evaluation User Safety Guidelines
WARNING
Always follow TI’s set-up and application instructions, including use of all interface components within their
recommended electrical rated voltage and power limits. Always use electrical safety precautions to help ensure
your personal safety and the safety of those working around you. Contact TI’s Product Information Center http://
support.ti.com for further information.
Save all warnings and instructions for future reference.
Failure to follow warnings and instructions may result in personal injury, property damage, or death due
to electrical shock and/or burn hazards.
The term TI HV EVM refers to an electronic device typically provided as an open-framed, unenclosed printed-
circuit board assembly. It is intended strictly for use in development laboratory environments, solely for qualified
professional users having training, expertise, and knowledge of electrical safety risks in development and
application of high-voltage electrical circuits. Any other use and/or application are strictly prohibited by Texas
Instruments. If you are not suitably qualified, you should immediately stop from further use of the HV EVM.
•Work Area Safety:
– Maintain a clean and orderly work area.
– A qualified observer or observers must be present any time circuits are energized.
– Effective barriers and signage must be present in the area where the TI HV EVM and its interface
electronics are energized, indicating operation of accessible high voltages can be present, for the purpose
of protecting inadvertent access.
– All interface circuits, power supplies, evaluation modules, instruments, meters, scopes, and other related
apparatus used in a development environment exceeding 50 VRMS/75 VDC must be electrically located
within a protected Emergency Power Off (EPO) protected power strip.
– Use a stable and non-conductive work surface.
– Use adequately insulated clamps and wires to attach measurement probes and instruments. No freehand
testing whenever possible.
•Electrical Safety:
As a precautionary measure, it is always a good engineering practice to assume that the entire EVM can
have fully accessible and active high voltages.
– De-energize the TI HV EVM and all its inputs, outputs, and electrical loads before performing any
electrical or other diagnostic measurements. Confirm that TI HV EVM power has been safely de-
energized.
– With the EVM confirmed de-energized, proceed with required electrical circuit configurations, wiring,
measurement equipment hook-ups, and other application needs, while still assuming the EVM circuit and
measuring instruments are electrically live.
– When EVM readiness is complete, energize the EVM as intended.
WARNING
WARNING: While the EVM is energized, never touch the EVM or its electrical circuits as
they could be at high voltages capable of causing electrical shock hazard.
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•Personal Safety:
– Wear personal protective equipment, for example, latex gloves, safety glasses with side shields, or both,
or protect EVM in an adequate lucent plastic box with interlocks from accidental touch.
•Limitation for Safe Use:
– EVMs are not to be used as all or part of a production unit.
Safety and Precautions
The EVM is designed for professionals who have received the appropriate technical training, and is designed
to operate from an AC power supply or a high-voltage DC supply. Please read this user's guide and the
safety-related documents that come with the EVM package before operating this EVM.
CAUTION
!
Do not leave the EVM powered when unattended.
WARNING
Hot surface! Contact may cause burns. Do not touch!
WARNING
High Voltage! Electric shock is possible when connecting board to live wire. Board should be handled with care by a
professional.
For safety, use of isolated test equipment with overvoltage and overcurrent protection is highly recommended.
General TI High Voltage Evaluation User Safety Guidelines www.ti.com
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2 EVM Characteristics
Unless otherwise specified, the following conditions apply: TA = 25ºC, IOUT1 = primary output current, IOUT2 =
secondary output current
Table 2-1. LM5168FQEVM Electrical Performance Characteristics
Parameter Test Conditions MIN TYP MAX UNITS
INPUT CHARACTERISTICS
Input voltage range, VVIN EVM input voltage operating range 20 48 115 V
Input voltage turn-on, VIN(ON)
Adjusted by EN/UVLO resistors
6.0 V
Input voltage turn-off, VIN(OFF) 5.6 V
Input voltage hysteresis, VIN(HYS) 0.4 V
Input current, no load, IIN(NL) IOUT = 0 A VIN = 48 V 13 mA
Input current, disabled, IIN(OFF) VEN/UVLO = 0 V, no EN divider VIN = 36 V 10 µA
OUTPUT CHARACTERISTICS
Output voltage, VOUT1 VIN = 48 V, IOUT1 = IOUT2 = 0A 10.0 V
Output voltage, VOUT2 VIN = 48 V, IOUT1=0 A, IOUT2 = 0A 10.0
Output current, IOUT1 VIN = 48 V, IOUT2 = 0 A 0.25 A
Output current, IOUT2 VIN = 48 V, IOUT1 = 0 A 0.25 A
Output voltage regulation, ΔVOUT1
Load regulation, VIN = 48 V IOUT1 = 0 A to 0.25
A, IOUT2 = 0 A
1 mV
Output voltage regulation, ΔVOUT2
Load regulation, VIN = 48 V IOUT1 = 0 A to 0.25
A, IOUT2 = 0 A
200
Output voltage regulation, ΔVOUT1
Load regulation, VIN = 48 V IOUT2 = 0 A to 0.25
A, IOUT1 = 0 A
7
Output voltage regulation, ΔVOUT2
Load regulation, VIN = 48 V IOUT2 = 0 A to 0.25
A, IOUT1 = 0 A
1000
Output voltage regulation, ΔVOUT1
Line regulation, IOUT1 = IOUT2
= 0 A
VIN = 24 V to 115 V 50
Output voltage regulation, ΔVOUT2
Line regulation, IOUT1 = IOUT2
= 0 A
VIN = 24 V to 115 V 750
Maximum output current from primary
output VIN = 48 V, IOUT2 = 0 A 0.27 A
Soft-start time, tSS 3.5 ms
SYSTEM CHARACTERISTICS
Switching frequency VIN = 36 V, IOUT1 = 0 A , IOUT2 = 0 A 730 kHz
Half-load efficiency IOUT1 = IOUT2 = 0.08 A VIN = 48 V 70%
Full load efficiency IOUT1 = IOUT2 = 0.125 A VIN = 48 V 76%
VIN = 60 V 72%
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3 LM5168FEVM Evaluation Module
The LM5168FEVM is configured to deliver a regulated 10-V output, 0.25 A at 750-kHz switching frequency, and
an additional 10-V floating output. The LM5168 uses a COT control architecture, with input voltage feedforward
to provide a constant frequency regulator with tightly regulated output voltage. This type of control requires
adequate voltage ripple at the FB input to achieve stable regulation. The LM5168FEVM is set up with type III
ripple injection to minimize the output voltage ripple while ensuring a stable regulator. The LM5168FEVM also
provides the option to use type I or type II ripple injection. See the LM516x-Q1 0.65/0.3-A, 120-V Step-Down
Converter w/ Fly-Buck Converter Capability Data Sheet for more information. An overall view of the LM516FEVM
and the schematic are shown in Figure 3-1 and Figure 4-1, respectively.
3.1 Quick Start Procedure
1. Connect the input voltage supply to the VIN connector (+ and –).
2. Connect the load or loads to the VOUT and the VOUT2 connectors (+ and –).
3. Set the input supply voltage to an appropriate level between 20 V to 115 V.
4. Turn on the power supply. The EVM powers up and provides VOUT = 10 V, and VOUT2 = 10 V.
See Figure 3-1 for the location of the connectors.
CAUTION
Caution Hot surface.
Contact may cause burns.
Do not touch.
Figure 3-1. LM5168FEVM Top View
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3.2 Detailed Descriptions
This section describes the connectors and the test points on the EVM and how to properly connect, set up, and
use the LM5168FEVM EVM. See Figure 3-1 for location of connectors and jumpers.
VOUT Output voltage of the converter
VOUT screw terminal connector. Apply load to this connector (+ and –). The VOUT test point is
used to monitor output voltage.
VOUT2 Secondary output voltage of the converter
VOUT2 screw terminal connector. One side of this output is connected to the primary ground
(GND) through a tie resistor, Rtie (R12). This resistor can be removed for a true floating voltage
source. Apply load to this connector (+ and –).
GND Ground of the converter
GND and GNDS test points. Used as ground test points for the EVM.
VIN Input voltage to the converter
VIN screw terminal connector. Apply input voltage to this connector (+ and –). The VIN test point is
used to monitor input voltage.
VINEMI Input voltage to input filter of the converter
If it is desired to use the built-in EMI filter on the EVM, then connect the input supply to the VINEMI
screw terminal connector (+ and –).
Input
Filter
EMI mitigation
An input EMI filter is provided on the EVM. Note L2 and C18 are not populated and must be
installed for the EMI filter to operate. Also, note that the maximum input voltage to the filter is 100
VDC.
EN/UVLO
Jumper
Set EN/UVLO pin options
Use this jumper to enable/disable the EVM. The resistors connected to this pin set the input UVLO
thresholds. Input UVLO thresholds are set to approximately 6 V and 5.6 V. These levels can be
changed by changing the values of R5 and R7. For external control of the device, these resistors
should be removed and the control signal applied to the center pin of the header. Note that for
accurate shutdown current measurement, these resistors must also be removed and the EN input
(center pin) grounded.
1. Jumper open (default setup): Device starts up and shuts down with UVLO.
2. Center pin connected to ON: Device starts up and shuts down without UVLO.
3. Center pin connected to OFF: Device is off.
PGOOD The PGOOD header used as a test point to monitor the power-good indicator. This flag indicates
whether the output voltage has reached its regulation level. PGOOD is an open-drain output that is
tied to VOUT through a 100-kΩ, resistor R10.
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5 PCB Layout
Figure 5-1 through Figure 5-4 show the board layout for the LM5168FEVM.
The 8-pin SO PowerPAD™ package offers an exposed thermal pad, which must be soldered to the copper
landing on the PCB for optimal thermal performance. The PCB consists of a 4-layer design. There are 2-oz
copper planes on the top and bottom and 1-oz copper mid-layer planes to dissipate heat with an array of thermal
vias under the thermal pad to connect to all four layers.
Figure 5-1. Top Layer
Figure 5-2. Mid-Layer 1 Ground Plane
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