Texas Instruments TPS54291EVM-431, Руководство пользователя, Страница: 7 / 18

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Test Set UP
V1: VIN, 0-15V voltmeter
V2: VOUT1 0-6V voltmeter
V3: VOUT2 0-4V voltmeter
4.1.3 Loads
LOAD1
The Output1 Load (LOAD1) should be an Electronic Constant Current Mode Load capable of 0-1.5Adc at
3.3V
LOAD2
The Output2 Load (LOAD2) should be an Electronic Constant Current Mode Load capable of 0-2.5Adc at
1.2V
4.1.4 Oscilloscope
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.
4.1.5 Recommended Wire Gauge
V
IN
to J1
The connection between the source voltage, VIN and J1 of HPA431 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
The power connection between J2 of HPA431 and LOAD1 can carry as much as 1.5Adc. The minimum
recommended wire size is AWG #18, with the total length of wire less than 2 feet (1 foot output, 1 foot
return).
J3 to LOAD2
The power connection between J3 of HPA431 and LOAD2 can carry as much as 2.5Adc. The minimum
recommended wire size is AWG #18, with the total length of wire less than 2 feet (1 foot output, 1 foot
return).
4.1.6 Other
FAN
This evaluation module includes components that can get hot to the touch, because this EVM is not
enclosed to allow probing of circuit nodes, a small fan capable of 200-400 lfm is recommended to reduce
component surface temperatures to prevent user injury. The EVM should not be left unattended while
powered. The EVM should not be probed while the fan is not running.
4.2 Equipment Setup
Shown in Figure 2 is the basic test set up recommended to evaluate the TPS54291EVM-431. Note that
although the return for J1, J2 and JP3 are the same system ground, the connections should remain
separate as shown in
Figure 2 .
4.2.1 Procedure
1. Working at an ESD workstation, make sure that any wrist straps, bootstraps or mats are connected
referencing the user to earth ground before power is applied to the EVM. Electrostatic smock and
safety glasses should also be worn.
2. Prior to connecting the DC input source, V
IN
, it is advisable to limit the source current from V
IN
to 2.0A
7 SLVU356 – January 2010 Using the TPS54291EVM-431 A 12V Input, 3.3V 1.5A and 1.2V 2.5A
Synchronous Buck Converter
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