AIC1620 datasheet(10/12 Pages) AIC

10 / 12 page

AIC1620/AIC1621/AIC1622

Component Selection

1. Inductor Selection

An inductor value of 22

µH performs well in most

applications. The AIC1620 series also work with

inductors in the 10

µH to 47µH range. An inductor

with higher peak inductor current tends a higher

output voltage ripple (IPEAK×output filter capacitor

ESR). The inductor’s DC resistance significantly

affects efficiency. We can calculate the maximum

output current as follows:

























−

OUT

OFF

LIM

OUT

)

MAX

(

OUT

where IOUT(MAX)=maximum output current in

amps

VIN=input voltage

L=inductor value in

µH

η=efficiency (typically 0.9)

tOFF=LX switch’off-time in µS

ILIM=0.45A or 0.8A

2. Capacitor Selection

The output voltage ripple relates with the peak in-

ductor current and the output capacitor ESR. Be-

sides output ripple voltage, the output ripple cur-

rent also needs to be concerned. The smaller the

capacitor ESR is, the higher the ripple current will

be. A filter capacitor with low ESR is helpful to

the efficiency and steady state output current of

AIC1620 series. Therefore HERMEI capacitor LT

series with 220

µF/6.3V is recommended. A

smaller capacitor (down to 10F with higher ESR)

is acceptable for light loads or in applications that

can tolerate higher output ripple.

3. PCB Layout and Grounding

Since AIC1622’s switching frequency can range

up to 500kHz, it makes AIC1622 become very

sensitive. So careful printed circuit layout is im-

portant for minimizing ground bounce and noise.

IC’s OUT pin should be as clear as possible. And

the GND pin should be placed close to the ground

plane. Keep the IC’s GND pin and the ground

leads of the input and output filter capacitors less

than 0.2in (5mm) apart. In addition, keep all con-

nection to the FB and LX pins as short as possi-

ble. In particular, when using external feedback

resistors, locate them as close to the FB as pos-

sible. To maximize output power and efficiency

and minimize output ripple voltage, use a ground

plane and solder the IC’s GND directly to the

ground plane. Following are the recommended

layout diagrams.

Figure 12. Top layer

Figure 13. Bottom layer

Figure 14. Placement

AIC1620 Datasheet(PDF) 10 Page - Analog Intergrations Corporation

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