Datasheet

3.4.8 Output Voltage Monitoring (TP18 and TP19)
4 Test Set UP
4.1 Equipment
4.1.1 Voltage Source
4.1.2 Meters
4.1.3 Loads
4.1.4 Oscilloscope
4.1.5 Recommended Wire Gauge
www.ti.com Test Set UP
TPS55386EVM-363 provides two test points for measuring the voltage generated by the module. This
allows the user to measure the actual module output voltage without losses from output cables and
connector losses. All output voltage measurements should be made between TP18 and TP19. To use
TP18 and TP19, connect a voltmeter positive terminal to TP18 and negative terminal to TP19. For Output
ripple measurements, TP18 and TP19 allow a user to limit the ground loop area by using the Tip and
Barrel measurement technique shown in Figure 3 All output ripple measurements should be made using
the Tip and Barrel measurement. Even this Tip and Barrel measurement technique increases the
measured switch edge noise. For improved output ripple measurement, measure the output ripple at the
output capacitor (C17)
V
IN
The input voltage source (V
IN
) should be a 0-15V variable DC source capable of 5Adc. Connect V
IN
to J1
as shown in Figure 3 .
A1: 0-3Adc, ammeter
V1: VIN, 0-15V voltmeter
V2: VOUT1 0-6V voltmeter
V3: VOUT2 0-4V voltmeter
LOAD1
The Output1 Load (LOAD1) should be an Electronic Constant Current Mode Load capable of 0-2Adc at
5.0V
LOAD2
The Output2 Load (LOAD2) should be an Electronic Constant Current Mode Load capable of 0-2Adc at
3.3V
OSCILLOSCOPE
A Digital or Analog Oscilloscope can be used to measure the ripple voltage on VOUT1 or VOUT2. The
Oscilloscope should be set for 1M Ω impedance, 20MHz Bandwidth, AC coupling, 1 µ s/division horizontal
resolution, 10mV/division vertical resolution for taking output ripple measurements. TP3 and TP4 or TP18
and TP19 can be used to measure the output ripple voltages by placing the oscilloscope probe tip through
TP3 or TP18 and holding the ground barrel to TP4 or TP19 as shown in Figure 3 . For a hands free
approach, the loop in TP4 or TP19 can be cut and opened to cradle the probe barrel. Using a leaded
ground connection may induce additional noise due to the large ground loop area.
V
IN
to J1
The connection between the source voltage, VIN and J1 of HPA241 can carry as much as 5 Adc. The
minimum recommended wire size is AWG #16 with the total length of wire less than 4 feet (2 feet input, 2
feet return).
J2 to LOAD1
SLVU273 – September 2008 Using the TPS55386EVM-363 A 12V Input, 5.0V & 3.3V Output, 3A Non-Synchronous Buck Converter 7
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