3 Detailed Descriptions
This section describes the connectors on the EVM and how to properly connect, set up, and use the EVM. See
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
the VOUT connector and the GND connector 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.
V
IN
Input voltage to the converter
The V
IN
connector connects to the input capacitors and the VIN pins of the LMQ61460-Q1. Connect
the supply voltage from a power supply or a battery between VIN and GND connectors as power
input to the device. The input voltage (V
IN
) range must be higher than 3.9 V for the device to start up
and above 3 V to maintain operation. A V
IN
higher than 6 V provides a regulated 5-V output voltage.
Maximum V
IN
is limited to 36 V to avoid damaging the device. The current limit on the supply must
be high enough to provide the needed supply current. The supply voltage must be connected to the
board with short and thick wires to handle the required input current at maximum load current. If long
cables are used to power up the board, damping must be provided by adding CFLT3 and RFLT3 to
avoid oscillation between the cable parasitic inductance and the existing low-ESR ceramic
capacitors.
VIN_EMI
Low EMI option
If the input filter is required, connect the supply voltage between VIN_EMI and GND_EMI. The
supply voltage must be connected to the board with short and thick wires.
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 for filter optimization. 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 V
IN
, which is connected to the V
IN
pins of the LMQ61460-Q1.
Conducted EMI arises from the operation of switching circuits.
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
automatically changes to forced PWM mode, maintaining a constant switching frequency over the
entire load range while the clock signal is present.
EN
To monitor the EN pin or control EN 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 so the IC turns on by default. Populate RENB to adjust UVLO. Apply a voltage to EN
to externally enable or disable the device.
Detailed Descriptions
SNVU698B – SEPTEMBER 2020 – REVISED DECEMBER 2020
LMQ61460EVM-400K User's Guide
5
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