Datasheet

Modifications
1-3
Introduction
1.3 Modifications
1.3.1 General
The TPS54314EVM is designed to demonstrate the small amount of board
space taken up by the TPS54314 electrical components. In addition, the EVM
can be used to evaluate different output filters by substituting an alternative
inductor for L1, or by using the optional pads for capacitors C2 and C10 (see
Figure 4–1). Because the feedback compensation is fixed by the internal
circuitry of the TPS54314, proper selection of the output inductor and output
capacitor ensures stability. The SWIFT Designer software tool or Texas
Instruments application note SLVA111 can be used to assist in the selection
of an output filter. Both SWIFT Designer and SLVA111 are available for
download at the Texas Instruments web site.
1.3.2 Switching Frequency
The TPS54314 is configured to switch at a frequency of 700 kHz. Alternatively
the EVM can be easily configured to switch at either 350 kHz or 550 kHz by
removing the frequency trimming resistor R3 and placing the shunt on jumper
JP1 in the proper location. Also, by changing the value of RT (R3), the
switching frequency can be trimmed to any value between 280 kHz and
700 kHz. A plot of the value of RT versus the switching frequency is given in
Figure 1–1.
Figure 1–1. Frequency Trimming Resistor Selection Graph
250
300
350
400
450
500
550
600
650
700
750
60 70 80 90 100 110 120 130 140 150 160 170 180
Switching Frequency – kHz
R – Resistance – Ω
1.3.3 Output Voltage
The EVM can be modified for different preset output voltages by using other
devices in the TPS5431x family. The only U1 component needs to be changed.
Table 1–2 lists the devices required for U1 for different output voltage options.