Datasheet

V =
OUT
0.765 •
(1+
R1
R2
−
)
V = V
OUT OUT_SET
(0.763 + 0.0017 ) 1 +· · (
R1
R2
¾
)
TPS54226
www.ti.com SLVSA14E –OCTOBER 2009–REVISED JULY 2011
DESIGN GUIDE
Step By Step Design Procedure
To begin the design process, the following application parameters must be known:
• Input voltage range
• Output voltage
• Output current
• Output voltage ripple
• Input voltage ripple
Figure 14 shows the schematic diagram for this design example.
Figure 14. Schematic Diagram
Output Voltage Resistors Selection
The output voltage is set with a resistor divider from the output node to the VFB pin. It is recommended to use
1% tolerance or better divider resistors. Start by using Equation 3 and Equation 4 to calculate V
OUT
.
To improve efficiency at very light loads consider using larger value resistors, too high of resistance is more
susceptible to noise and voltage errors from the VFB input current are more noticeable.
For output voltage from 0.76 V to 2.5 V:
(3)
For output voltage over 2.5 V:
(4)
Where:
V
OUT_SET
= Target V
OUT
voltage
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