This section describes the test points and connectors on the EVM and how to properly connect, set up, and use the LMR60460QEVM.
The EVM uses the LMR60460-Q1 converter, which
includes MODE/SYNC capability. This statement means that the device can operate in
pulse frequency modulation (PFM) light-load mode when this pin is tied to GND. TI
has observed additional output voltage ripple at input voltages close to the output
voltage when the device is operating in PFM light-load mode. To see improved
performance, TI recommends to configure the EVM to operate in forced pulse width
modulation (FPWM) mode. To access the FPWM light-load operating mode, depopulate
resistor R8 and populate resistor R6.
The test setup consists of the following instruments in addition to the EVM board.
- Power supply: the input DC voltage source
must be capable of supplying 36V and 4A.
- Load: the load must be an electronic,
constant-current (CC) or constant-resistance (CR) mode load, capable of supporting 6A of
load current at 5.0V. Disconnect the electronic load when performing no-load input current
tests.
- Multimeters:
- Voltmeter 1: measures input
voltage at VIN+ (TP14) and VIN– (TP15)
- Voltmeter 2: measures output
voltage at VOUT (TP16) and VOUT– (TP17)
- Ammeter 1: measures input
current.
- Ammeter 2: measures output
current.
- Oscilloscope: with the scope set to 20MHz
bandwidth and AC coupling, measure the output voltage ripple directly across an output
capacitor with a short ground lead. Place the oscilloscope probe tip on the positive
terminal of the output capacitor, and the ground lead on the negative terminal of the
output capacitor. TI does not recommend using a long-leaded ground connection because the
connection can induce additional noise due to a large ground loop. To measure other
waveforms, adjust the oscilloscope as necessary.