Texas Instruments TPS40075EVM, Руководство пользователя, Страница: 6 / 21

To operate with a 5-V input, two resistors need to be changed. R10 (R
KFF
) sets the voltage ramp amplitude and
needs to be reduced to 53.6 kΩ to lower the UVLO to 3.9 V for 5 V operation. In addition, a 330-kΩ resistor
should be added at R15 to prevent an internal race condition during soft start.
3.4 Enable
To disable the output and force the power MOSFETs into a high-impedance tri-state, connect TP21 to TP19. This
drives the base of Q3 and discharges the soft-start capacitor and shuts down the TPS40075 Controller.
4 Test Setup
4.1 Equipment
4.1.1 Voltage Source
V
12V_IN
The input voltage source (V
12V_IN
) should be a variable DC source between 0 V and 15 V, and capable of 5 A
DC
.
Connect V
12V_IN
to J1 as shown in Figure 4-2 .
4.1.2 Meters
• A1: 0 A to 5 A
DC
, ammeter
• V1: V
12V_IN
, 0-V to 15-V voltmeter
• V2: V
1V5_OUT
0-V to 5-V voltmeter
4.1.3 Loads
4.1.3.1 LOAD1
The output load (LOAD1) should be an electronic constant current mode load capable of 0 A
DC
–15 A
DC
at 1.5V.
4.1.4 Recommended Wire Gauge
4.1.4.1 V
12V_IN
to J1
The connection between the source voltage, V12V_IN and J1 of HPA187 can carry as much as 3 A
DC
. The
minimum recommended wire size is AWG #16 with the total length of wire less than four feet (2-feet input, 2-feet
return).
4.1.4.2 J2 to LOAD1 (Power)
The power connection between J2 of HPA187 and LOAD1 can carry as much as 15 A
DC
. The minimum
recommended wire size is 2 × AWG #16, with the total length of wire less than four feet (2-feet output, 2-feet
return).
4.1.4.3 J3 to LOAD1 (Remote Sense)
If remote sense is used, the remote sense connection between J3 of HPA187 and LOAD1 can carry less than 1
A
DC
. The minimum recommended wire size is AWG #22, with the total length of wire less and four feet (2-feet
output, 2-feet return).
4.1.5 Other
4.1.5.1 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 between 200 LFM and 400 LFM is required to reduce
component surface temperatures to prevent user injury. The EVM should not be left unattended while powered
or probed while the fan is not running.
4.1.5.2 Oscilloscope
A 60-MHz or faster oscilloscope can be used to determine the ripple voltage on 1V5_OUT. The oscilloscope
should be set for the following to take output ripple measurements:
• 1-MΩ impedance
• AC coupling
• 1-μs/division horizontal resolution
• 20-mV/division vertical resolution
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6 TPS40075 Buck Controller Evaluation Module User's Guide SLUU254A – DECEMBER 2006 – REVISED JANUARY 2022
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