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The LM3475 evaluation board is provided as a tool for developing DC/DC converters based on the LM3475 IC. As shown in Figure 3-1, the evaluation board is configured to provide an output of 2.5 V at up to 2 A from an input up to 10 V. The corresponding bill of material is given in Table 3-1. Typical efficiencies are shown in Figure 3-2 and Figure 3-3. Figure 4-1 and Figure 4-2 show the board layout.
To aid in the design and evaluation of DC/DC buck converters based on the LM3475 controller, the LM3475 evaluation board can be easily re-configured for different output voltages.
Vout can be set using RFB1, as shown in Equation 1:
where
See the device-specific data sheet before changing any component values since additional design adjustments can be required.
A feedforward capacitor, CFF, is placed on the board, which will increase operating frequency. However, the speed up effect decreases with lower output voltage and is negligible below 1.6-V output.
A 0 Ω is used to pull up the EN pin for always on operation. The enable pin can be pulled low at the EN post to shutdown the device. If this resistor is removed, any analog level signal can be used to enable and disable the device.
Designator | Part Description | Part Number |
---|---|---|
CIN | 10 µF, 16-V ceramic | Yuden EMK325BJ106MN |
COUT | 100 µF, 6-V tantalum | AVX TPSY107M006R0100 |
CFF | 1 nF, 25-V ceramic | VJ1206Y102KXXA |
D1 | Schottky 20 V, 2 A | Central CMSH2-20L |
L1 | 10 µH, 3.1 A | Sumida CDRH103R100 |
Q1 | Si 2343 30 V, 2.5 A | Vishay Si2343 |
RFB2 | 1 kΩ | Vishay CRCW08051001F |
RFB1 | 2.15 kΩ | Vishay CRCW08052151F |
R2 | 0 Ω | Vishay CRCW08050R00F |