Test Setup and Procedure
7
SNVU609B – October 2018 – Revised April 2020
Copyright © 2018–2020, Texas Instruments Incorporated
LM5180-Q1 Dual-Output EVM User's Guide
5.2
Test Equipment
Voltage Source:
The input voltage source V
IN
must be a 0–65-V variable DC source.
Multimeters:
•
Voltmeter 1:
Input voltage at VIN+ to VIN–. Set voltmeter to an input impedance of 100 M
Ω
.
•
Voltmeter 2:
Output voltage at VOUT1 to SGND. Set voltmeter to an input impedance of 100 M
Ω
.
•
Voltmeter 3:
Output voltage at VOUT2 to SGND. Set voltmeter to an input impedance of 100 M
Ω
.
•
Ammeter 1:
Input current. Set ammeter to 1-second aperture time.
•
Ammeter 2:
Load current, output #1. Set ammeter to 1-second aperture time.
•
Ammeter 3:
Load current, output #2. Set ammeter to 1-second aperture time.
Electronic Loads:
The loads must be electronic constant-resistance (CR) or constant-current (CC) mode
load capable of 0 Adc to 300 mAdc up to 15 V. For a no-load input current measurement, disconnect the
electronic load as it may draw a small residual current.
Oscilloscope:
With the scope set to 20-MHz bandwidth and AC coupling, measure the output voltage
ripple directly across an output capacitor with a short ground lead normally provided with the scope probe.
Place the oscilloscope probe tip on the positive terminal of the output capacitor, holding the ground barrel
of the probe through the ground lead to the negative terminal of the capacitor. TI does not recommend
using a long-leaded ground connection because this may induce additional noise given a large ground
loop. To measure other waveforms, adjust the oscilloscope as needed.
Safety:
Always use caution when touching any circuits that may be live or energized.
5.3
Recommended Test Setup
5.3.1
Input Connections
•
Prior to connecting the DC input source, set the current limit of the input supply to 100 mA maximum.
Ensure the input source is initially set to 0 V and connected to the VIN+ and VIN– connection points as
shown in
. An additional input bulk capacitor is recommended to provide damping if long input
lines are used.
•
Connect voltmeter 3 at VIN+ and VIN– connection points to measure the input voltage.
•
Connect ammeter 3 to measure the input current and set to at least 1-second aperture time.
5.3.2
Output Connections
•
Connect electronic loads to VOUT1, VOUT2, and SGND connections as shown in
. Set the
load to constant-resistance mode or constant-current mode at 0 A before applying input voltage.
•
Connect voltmeters 1 and 2 at VOUT1, VOUT2, and SGND connection points to measure the output
voltages.
•
Connect ammeters 1 and 2 to measure the output currents.
5.4
Test Procedure
5.4.1
Line and Load Regulation, Efficiency
•
Set up the EVM as described above.
•
Set load to constant resistance or constant current mode and to sink 10 mA.
•
Increase input source from 0 V to 24 V; use voltmeter 3 to measure the input voltage.
•
Increase the current limit of the input supply to 500 mA.
•
Using voltmeters to measure the respective output voltages, vary both loads from 10 mA to 200 mA
DC; V
OUT1
and V
OUT2
must remain within the load regulation specification.
•
Set the load currents to 100 mA (50% rated load) and vary the input source voltage from 10 V to 65 V;
V
OUT1
and V
OUT2
must remain within the line regulation specification.
•
Decrease loads to 10 mA. Decrease input source voltage to 0 V.
