Detailed Descriptions
4
SNVU579 – September 2017
Copyright © 2017, Texas Instruments Incorporated
LM73605 / LM73606 EVM User’s Guide
3
Detailed Descriptions
This section describes the connectors and the test points on the EVM and how to properly connect, set up
and use the LM73605/LM73606 EVM. See
for a top view of the EVM.
VOUT —
Output voltage of the converter.
VOUT connector and test point connect to the power inductor and the output capacitors. Connect
the loading device between VOUT and PGND connectors to provide loading to the converter.
Connect the loading device to the board with short and thick wires to handle the large DC output
current.
PGND —
Ground of the converter.
It is connected to the PGND and AGND of the device, as well as the input and output capacitors.
PGND is the current return path for both supply voltage and load. Connect to supply and load
grounds with short and thick wires.
VIN —
Input voltage to the converter.
VIN connector and test point connect to the input capacitors and the PVIN pins of the
LM73605/LM73606. Connect the supply voltage from a power supply or a battery between VIN and
PGND connectors as power input to the board. The voltage range should be higher than 3.5 V for
the device to be active. V
IN
higher than 6 V provides regulated 5 V output voltage. V
IN
should be no
higher than 36 V to avoid damaging the device. The current limit on the supply should be high
enough to provide the needed supply current. Otherwise the supply voltage will not maintain the
desire voltage. The supply voltage should 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, the damping
capacitor C
BULK
located on the bottom side of board should be added, 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 voltage and the LM73605/6, connect the supply
voltage between VIN-EMI and GND-EMI. The supply voltage should be connected to the board with
short and thick wires to handle pulsing input current.
GND-EMI —
Ground connection near the input filter
This is the current return path for the supply connected to VIN-EMI. It provides a direct connection
to the input filter capacitors to best filter the conducted noises generated from the PCB. Use VIN-
EMI and GND-EMI connection if input filter is used and conducted EMI test is desired.
Input Filter—
Prevent noise from contaminating supply voltage
The input filter consists of C-FLTs, L-IN and CBULK, located on the bottom side of the PCB. 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 the V
IN
net, which is connected to the
PVIN pins of the LM73605/LM73606 and the input capacitors. Note that the input filter components
are not mounted on the PCB by default.
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 of the buck converter via physical contact of the conductors.
Without control, excessive input voltage ripple can compromise operation of the source. The input
filter helps to smooth out the voltage perturbations leading to the source.
Preliminary EMI test results are shown in
.
EN —
Test point to monitor the EN pin of the device
This test point is to monitor the voltage on the device EN pin.
EN Jumper —
Set EN pin options
As noted on the board, this jumper is to select which voltage is used to enable the device.
1. PIN-1 to PIN-2: EN is connected to EN-EXT test point through a resistor divider;
2. PIN-2 to PIN-3 (default): EN is connected to V
IN
through a resistor divider.