AiT Semiconductor Inc.
A7231A
DC-DC CONVERTER BUCK (STEP-DOWN)
500kHz, 3A, 16V SYNCHRONOUS
www.ait-ic.com
APPLICATIONS INFORMATION
Setting Output Voltages
The external resistor divider is used to set the output voltage (see Typical Application on page 1). The
feedback resistor R1 also sets the feedback loop bandwidth with the internal compensation capacitor. Choose
R1 to be around 300kΩ for optimal transient response. R2 is then given by:
Selecting the Inductor
Use a 2.2μH to 10μH inductor with a DC current rating of at least 25% percent higher than the maximum load
current for most applications. For highest efficiency, select an inductor with a DC resistance less than 15mΩ.
For most designs, derive the inductance value from the following equation.
L =
Where ΔIL is the inductor ripple current. Choose an inductor current approximately 30% of the maximum load
current. The maximum inductor peak current is:
IL(MAX) = ILOAD
+
Under light-load conditions (below 100mA), use a larger inductor to improve efficiency.
Selecting the Output Capacitor
The output capacitor (C2) maintains the DC output voltage. Use ceramic, tantalum, or low- ESR electrolytic
capacitors. Use low ESR capacitors to limit the output voltage ripple. Estimate the output voltage ripple with:
ΔVOUT
=
Where L is the inductor value and RESR is the equivalent series resistance (ESR) of the output capacitor.
For ceramic capacitors, the capacitance dominates the impedance at the switching frequency and causes
most of the output voltage ripple. For simplification, estimate the output voltage ripple with:
ΔVOUT
=
REV1.0
- MAY 2018 RELEASED -
- 10 -
AITSEMI [ AiT Semiconductor ]
