Detailed Descriptions
5
SNVU621C – May 2019 – Revised December 2019
Copyright © 2019, Texas Instruments Incorporated
LM61460-Q1 EVM User's Guide
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
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.
V
IN
—
Input voltage to the converter
The V
IN
connector 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
IN
higher than 6 V provides regulated 5 V output voltage. V
IN
must be no higher than 36 V to avoid
damaging the device. After start-up, the device stays active until V
IN
drops 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.
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 V
IN
, which is connected to the V
IN
pins 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.