Texas instruments LM61460-Q1 User Manual
User's Guide
SNVU621C–May 2019–Revised December 2019
LM61460-Q1 EVM User's Guide
The LM61460-Q1 evaluation module (EVM) is designed to help customers evaluate the performance of
the LM61460-Q1 synchronous step-down voltage converter. This EVM implements the LM61460-Q1 in a
14-pin wettable flanks Hotrod™ package, as shown in Table 1. It is capable of delivering 5-V output
voltage and up to 6-A load current with exceptional efficiency and output accuracy in a very small solution
size. The EVM provides multiple power connectors and test points. It also provides a good layout
example, which is optimized for EMI and thermal performance.
Table 1. Device and Package Configurations
CONVERTER IC PACKAGE
U1 LM61460-Q1 14-pin wettable flanks Hotrod package 4.0 mm × 3.5 mm × 1.0 mm
Figure 1. LM61460EVM Front Figure 2. LM61460EVM Angle
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LM61460-Q1 EVM User's Guide
1
Introduction
Contents
1 Introduction ................................................................................................................... 2
2 Quick Start.................................................................................................................... 3
3 Detailed Descriptions........................................................................................................ 5
4 Schematic..................................................................................................................... 6
5 Board Layout ................................................................................................................. 9
6 LM61460EVM Board Test Results....................................................................................... 10
7 Bill of Materials ............................................................................................................. 16
Trademarks
Hotrod is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
1 Introduction
1.1 LM61460 Synchronous Step-Down Voltage Converter
The LM61460-Q1 device is an easy-to-use synchronous step-down DC/DC converter capable of driving
up to 6 A of load current from a supply voltage ranging from 3 V to 36 V. The LM61460-Q1 provides
exceptional efficiency and output accuracy in a very small solution size. The LM61460-Q1 is capable of
delivering 6 A of load current and is peak current limit controlled. The following are additional features that
provide both flexible and easy-to-use solutions for a wide range of applications:
• Adjustable switching frequency
• Synchronization to an external clock
• FPWM variant (LM61460AFS)
• Power-good flag
• Precision enable
Automatic frequency foldback at light load and optional external bias improve efficiency over the entire
load range. The device requires few external components and has a pinout designed for optimal EMI and
thermal performance. Protection features include the following:
• Thermal shutdown
• Input undervoltage lockout
• Cycle-by-cycle current limiting
• Hiccup short-circuit protection
The LM61460-Q1 device is pin-to-pin compatible with the LM61440-Q1 for easy output current scaling.
For a quick reference, Figure 3 shows the pin configuration of the LM61460-Q1 and Figure 4 shows the
simplified schematic. See the LM61460-Q1 Automotive 3-V to 36-V, 6-A, Low-Noise Synchronous Step-
Down Converter Data Sheet for more detailed feature descriptions and design guide.
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2
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LM61460-Q1
RESET
EN/SYNC
RT
PGND1
AGND
VCC
CBOOT
SW
FB
BIAS
RBOOT
3.0 V to 36 V input
VIN1
PGND2
VIN2
3.5 mm
4 mm
BIAS
CBOOT
RBOOT
EN/
SYNC
RESET
VIN1
VIN2
PGND1
PGND2
SW
FB
AGND
VCC
RT
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/RESET and PGOOD are used to describe the same device
pin throughout this document and other documents. Be aware
that these pin nomenclatures are used to describe the same
pin.
Figure 3. LM61460-Q1 Pin Configuration (Top View) Figure 4. LM61460-Q1 Schematic
1.2 LM61460-Q1 Evaluation Module
The LM61460-Q1 EVM has the board populated with the LM61460 in either one of two variants. Based on
the label populated, you can figure out which device trim is populated on the EVM and the corresponding
features. This board uses the LM61460-Q1 and limiting current to 6 A and comes with auto mode enabled.
Introduction
LABEL U1 I
LM61460EV
M-AS-400K
LM61460EV
M-FS-400K
LM61460AA
SQRJRRQ1
LM61460AF
SQRJRRQ1
2 Quick Start
1. Connect the voltage supply between the VIN and GND connectors or between VIN_EMI and
GND_EMI to include the on-board input filter in the input path. Use short and thick gauge wires to
minimize inductance and IR drop. Note that sense points for VINand V
2. Connect the load of the converter between VOUT and GND connectors using short and thick wires.
3. Set the supply voltage at an appropriate level between 6 V to 36 V. The 6 V minimum ensures enough
head room for V
appropriate level to supply needed current and protection.
4. Turn on the power supply. With the default configuration, the EVM powers up and provides V
5. Monitor the output voltage with sense points. The maximum load current must be 6 A with the
LM61460-Q1. Note that the maximum output current may need to derate if ambient temperature is
high, especially if device is operated at higher frequency, ie: 2.2MHz.
See Figure 5 for connector locations.
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OUT
Table 2. EVM Variants
OUT
SWITCHING
FREQUENCY
6 A 400 kHz 3 to 36 V 5 V Enabled Disabled Enabled
6 A 400 kHz 3 to 36 V 5 V Disabled Enabled Enabled
V
IN
RANGE
OUT
AUTO
MODE
FPWM SPREAD SPECTRUM
are provided.
OUT
V
to equal 5 V at a 6 A load current. Set the current limit of the supply to an
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OUT
= 5 V.
3
CAUTION
Caution Hot surface.
Contact may cause burns.
Do not touch.
Quick Start
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Figure 5. Top View of LM61460-Q1 EVM
4
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3 Detailed Descriptions
This section describes the connectors on the EVM and how to properly connect, set up, and use the EVM.
See Figure 5 for a top view of the EVM.
VOUT —Output voltage of the converter
VOUT connectors connect to the power inductor and output capacitors. Connect the load between
VOUT connector and the GND connector right next to it to provide load current. Connect the
loading device to the board with short and thick wires to handle the large DC output current.
GND —Ground of the converter
The GND is connected to the PGND and AGND pins of the device, as well as the ground of the
input and output capacitors. The GND connections next to VIN, VIN_EMI, and VOUT connectors
are meant for current return path for the supply voltage and load, respectively. Connectors are
provided in pairs to allow easy and accurate sensing of voltages. Connect to supply and load
grounds with short and thick wires. Other GND connectors are for signal measurement and probing.
VIN— Input voltage to the converter
The VINconnector connects to the input capacitors and the VIN pins of the LM61460-Q1. Connect
the supply voltage from a power supply or a battery between VIN and GND connectors as power
input to the device. The voltage range must be higher than 3.9 V for the device to start up. V
higher than 6 V provides regulated 5 V output voltage. VINmust be no higher than 36 V to avoid
damaging the device. After start-up, the device stays active until VINdrops below 3 V. The current
limit on the supply must be high enough to provide the needed supply current. Otherwise, the
supply voltage does not maintain the desired voltage. The supply voltage must be connected to the
board with short and thick wires to handle the pulsing input current. If long cables are used to
power up the board, damping must be provided by added CFLT3 and RFLT3 to avoid oscillation
between the cable parasitic inductance and the low-ESR ceramic capacitors.
Detailed Descriptions
IN
VIN_EMI —Input voltage to input filter of the converter
If the input filter is desired between the supply and the LM61460-Q1, connect the supply voltage
between VIN_EMI and GND_EMI. The supply voltage must be connected to the board with short
and thick wires to handle pulsing input current.
The input filter consists of the following: CF1, CF2, CF3, CF4, CF5, CF6, and L2. CD1, CD2, RD1,
and RD2 are provided to allow more options to during filter design. To include the input filter in the
power path, connect the supply voltage between the VIN_EMI and GND_EMI connectors. The
output of the filter is connected to VIN, which is connected to the VINpins of the LM61460-Q1 and
the input capacitors.
Conducted EMI arises from the normal operation of switching circuits. The ON and OFF actions of
the power switches generate large discontinuous currents. The discontinuous currents are present
at the input side of buck converters. Voltage ripple generated by discontinuous currents can be
conducted to the voltage supply for the buck converter. Without filtering, excessive input voltage
ripple can compromise operation of other circuits connected to this source. The input filter helps
smooth out the voltage perturbations leading to less noise at the power source.
GND_EMI —Ground return for the input filter
This is the current return path for the supply connected to VIN_EMI. It provides a short-loop
connection to the input filter capacitors to best filter the conducted noise generated from the PCB.
Use VIN_EMI and GND_EMI connection if input filter is used and conducted EMI test is desired.
CLK —For synchronization clock input
The CLK input connector is designed for external clock input to the EN/SYNC pin. Switching action
of the buck is synchronized to the external clock when it is present. The operation mode changes to
forced PWM mode automatically, maintaining a constant switching frequency at light load.
EN — To monitor the EN pin or input EN control signal
This test point is used to monitor the voltage on the device EN pin. By default, the EN pin is
connected to the mid-point of an enable divider. Note that the lower resistor in this divider, RENB, is
not populated.
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Schematic
PG — To monitor the PGOOD/RESET pin
The PGOOD flag indicates whether the output voltage is within the regulation band. The PGOOD
pin of the device is an open-drain output and it is pulled up to V
resistor. This flag is high impedance when the output voltage is in regulation.
Vinj —To aid when making bode plots
There is a low value resistor, Rinj, between VOUT and this node. This feedback divider of the board
is connected to this node as well. Stimulus can be applied between this node and VOUT when
taking measurements for bode plots.
VOUTS —Kelvin sensing for VOUT
This connector is provided to allow V
VINS —Kelvin sensing for VIN
This connector is provided to allow VINto be measured more accurately.
4 Schematic
The bill of materials from Table 2 is tabulated in Section 7. In addition, Figure 6 shows the corresponding
schematic.
OUT
to be measured more accurately.
OUT
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on this board through a pullup
6
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Schematic
NOTE: Long leads and additional inductance in used to power the DC/DC may cause issues for ideal device operation. RD2, CD2, RD1, and
CD1 are placeholders for damping networks to be populated. For more information regarding this topic, reference the EMI Filter
Components and Their Nonidealities for Automotive DC/DC Regulators Technical Brief.
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Figure 6. LM61460-AS-400K Rev A EVM Schematic
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LM61460-Q1 EVM User's Guide
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Schematic
4.1 Alternative BOM Configurations
Table 3. Different BOM Configurations
VOUT FREQUENCY RFBB RT COUT CIN + CHF L1
3.3 V 400 kHz 43.2 kΩ 33.2 kΩ 6 x 22 µF 2 x 4.7 µF + 2 x
3.3 V 2100 kHz 43.2 kΩ 6.04 kΩ 3 x 22 µF 2 x 4.7 µF + 2 x
5 V 400 kHz 24.9 kΩ 33.2 kΩ 4 x 22 µF 2 x 4.7 µF + 2 x
5 V 2100 kHz 24.9 kΩ 6.04 kΩ 3 x 22 µF 2 x 4.7 µF + 2 x
100 nF
100 nF
100 nF
100 nF
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4.7 µH
(XHMI6060)
1 µH (XEL5030)
4.7 µH
(XHMI6060)
1 µH (XEL5030)
8
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