AAT1123 데이터 시트보기 (PDF) - Skyworks Solutions

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AAT1123

1MHz Step-Down Converter

Skyworks Solutions 

for VIN = 2 x VO

I = RMS(MAX)

IO

2

The term

VO

VIN

·

⎛⎝1 -

VO ⎞

VIN ⎠

appears in both the input voltage

ripple and input capacitor RMS current equations and is

a maximum when VO is twice VIN. This is why the input

voltage ripple and the input capacitor RMS current ripple

are a maximum at 50% duty cycle.

The input capacitor provides a low impedance loop for

the edges of pulsed current drawn by the AAT1123. Low

ESR/ESL X7R and X5R ceramic capacitors are ideal for

this function. To minimize stray inductance, the capaci-

DATA SHEET

AAT1123

1MHz Step-Down Converter

tor should be placed as closely as possible to the IC. This

keeps the high frequency content of the input current

localized, minimizing EMI and input voltage ripple.

The proper placement of the input capacitor (C2) can be

seen in the evaluation board layout in Figure 2.

A laboratory test set-up typically consists of two long

wires running from the bench power supply to the eval-

uation board input voltage pins. The inductance of these

wires, along with the low-ESR ceramic input capacitor,

can create a high Q network that may affect converter

performance. This problem often becomes apparent in

the form of excessive ringing in the output voltage dur-

ing load transients. Errors in the loop phase and gain

measurements can also result.

Figure 2: AAT1123 Evaluation Board

Top Side.

Figure 3: Exploded View of Evaluation

Board Top Side Layout.

Figure 4: AAT1123 Evaluation Board

Bottom Side.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

201975B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013

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