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4 Test Setup
4.1 Test and Configuration Software
To change any of the default configuration parameters on the EVM, it is necessary to obtain the TI Fusion
Digital Power Designer software.
4.1.1 Description
The Fusion Digital Power Designer is the graphical user interface (GUI) used to configure and monitor the
Texas Instruments TPS40422 power controller on this evaluation module. The application uses the
PMBus protocol to communicate with the controller over serial bus by way of a TI USB adapter (see
Figure 3).
4.1.2 Features
Some of the tasks you can perform with the GUI include:
• Turn on or off the power supply output, either through the hardware control line or the PMBus
operation command.
• Monitor real-time data. Items such as input voltage, output voltage, output current, temperature, and
warnings and faults are continuously monitored and displayed by the GUI.
• Configure common operating characteristics such as VOUT trim and margin, UVLO, soft-start time,
warning and fault thresholds, fault response, and ON/OFF.
This software is available for download at http://www.ti.com/tool/fusion_digital_power_designer
4.2 Test Equipment
Voltage Source: The input voltage source VIN must be a 0-V to 14-V variable dc source capable of
supplying 15 Adc. Connect VIN to J5 as shown in Figure 2.
Multimeters: It is recommended to use three separate multimeters as shown in Figure 2. One meter to
measure Vin, one to measure Vout1 and the third to measure Vout2.
Output Load: Two variable electronic loads are recommended for the test setup as shown in Figure 2.
Load 1 must be capable of 25 A at voltages as low as 0.9 V. Load 2 must be capable of 20 A at voltages
as low as 3 V.
Oscilloscope: An oscilloscope is recommended for measuring output noise and ripple. Output ripple must
be measured using a Tip-and-Barrel method or better as shown in Figure 4.The scope must be adjusted
to 20-MHz bandwidth, ac coupling at 50 mV/division, and must be set to 1-µs/division.
Fan: During prolonged operation at high loads, it may be necessary to provide forced air cooling with a
small fan aimed at the EVM. The temperature of the devices on the EVM must be maintained at less than
105°C.
USB-to-GPIO Interface Adapter: A communications adapter is required between the EVM and the host
computer. This EVM was designed to use the Texas Instruments USB-to-GPIO Adapter (see Figure 3).
This adapter can be purchased at http://www.ti.com/tool/usb-to-gpio.
Recommended Wire Gauge: It is recommended that the voltage drop in the load wires does not exceed
0.2 V total in order to keep the voltage at the load above 1 V. See the following table for recommended
wire gauge and length to achieve a voltage drop of no more than 0.2 V at a 20-A load.
Ohms per Foot Load Wires Combined Length Each Wire Length
AWG Gauge
(Ω) (Ft) (Ft)
12 1.59E-3 6.30 3.15
14 2.53E-3 3.96 1.98
16 4.02E-3 2.49 1.25
18 6.39E-3 1.57 0.78
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Using the PWR091EVM Dual-Output DC/DC Analog With PMBus Interface SLVU638–January 2012
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