AIC1611 데이터 시트보기 (PDF) - Analog Intergrations

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AIC1611

High Efficiency Synchronous Step-Up DC/DC Converter

Analog Intergrations 

AIC1610/AIC1611

formance

Shutdown

The whole circuit is shutdown when VSHDN is low.

At shutdown mode, the current can flow from battery

to output due to body diode of the P-MOSFET. VOUT

falls to approximately Vin-0.6V and LX remains high

impedance. The capacitance and load at OUT de-

termine the rate at which VOUT decays. Shutdown

can be pulled as high as 6V. Regardless of the volt-

age at OUT.

Selecting the Output Voltage

VOUT can be simply set to 3.3V/5.0V by connecting

FB pin to OUT/GND due to the use of internal resis-

tor divider in the IC (Fig.32 and Fig.33). In order to

adjust output voltage, a resistor divider is connected

to VOUT, FB, GND (Fig.34). Vout can be calculated

by the following equation:

R5=R6 [(VOUT / VREF )-1] .....................................(1)

Where VREF =1.23V and VOUT ranging from 1.8V to

5.5V. The recommended R6 is 240KΩ.

Low-Battery Detection

AIC1610 series contains an on-chip comparator with

50mV internal hysteresis (REF, REF+50mV) for low

battery detection. If the voltage at LBI falls below the

internal reference voltage. LBO ( an open-drain out-

put) sinks current to GND.

Component Selection

1. Inductor Selection

An inductor value of 22µH performs well in most

applications. The AIC1610 series also work with

inductors in the 10µH to 47µH range. An induc-

tor 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:

IOUT(MAX)

=

VIN

VOUT



ILIM



−

t OFF



VOUT − VIN

2×L

η

……………………………………………………(2)

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=1.0A or 0.65A

2. Capacitor Selection

The output ripple voltage relates with the peak

inductor current and the output capacitor ESR.

Besides output ripple voltage, the output ripple

current also needs to be concerned. A filter ca-

pacitor with low ESR is helpful to the efficiency

and steady state output current of AIC1610 se-

ries. Therefore NIPPON tantalum capacitor

MCM series with 100µF/6V is recommended. A

smaller capacitor (down to 47μ F with higher

ESR) is acceptable for light loads or in applica-

tions that can tolerate higher output ripple.

3. PCB Layout and Grounding

Since AIC1610’s switching frequency can range

up to 500kHz, it makes AIC1610 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 ca-

pacitors less than 0.2in (5mm) apart. In addition,

keep all connection to the FB and LX pins as

short as possible. In particular, when using ex-

ternal feedback resistors, locate them as close

to the FB as possible. To maximize output pow-

er and efficiency and minimize output ripple

voltage, use a ground plane and solder the IC’s

12

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