AIC3413 datasheet(8/10 Pages) AIC

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AIC3413

 APPLICATION INFORMATION

The AIC3413 is a synchronous step-up DC-DC con-

verter. It is based on a slope compensated current

mode PWM control topology. It operates at a fixed

frequency of 1.2MHz. At the beginning of each clock

cycle, the main switch (NMOS) is turned on and the

inductor current starts to ramp. After the maximum

duty cycle or the sense current signal equals the error

amplifier (EA) output, the main switch is turned off and

the synchronous switch (PMOS) is turned on. The de-

vice can operate with an input voltage below 1V; the

typical start-up voltage is 0.9V.

Current Limit

The over current protection is to limit the switch current.

The output Voltage will be dropped when over current

is happened. The current limit amplifier will shut the

N-MOS switch off once the current exceeds its thresh-

old. The current amplifier delay to output is about 100

nS.

Anti-Ringing Control

An anti-ringing circuitry is included to remove the high

frequency ringing that appears on the SW pin when the

inductor current goes to zero. In this case, a ringing on

the SW pin is induced due to remaining energy stored

in parasitic components of switch and inductor. The

anti-ringing circuitry clamps the voltage internally to the

battery voltage and therefore dampens this ringing.

Zero Current Comparator

The zero current comparator monitors the inductor

current to the output and shuts off the synchronous

rectifier once the current is below 20 mA, This prevents

the inductor current from reversing in polarity improv-

ing efficiency at light loads.

Device Shutdown

When SHDN is set logic high, the AIC3413 is put into

active mode operation. If SHDN is set logic low, the

device is put into shutdown mode and consumes less

than 1

μA of current. At the shutdown mode, the syn-

chronous switch will turn off and the output voltage of

AIC3413 step-up converter will reduce to 0V.After

start-up, the internal circuitry is supplied by VOUT,

however, if shutdown mode is enabled, the internal

circuitry will be supplied by the input source again.

Adjustable Output Voltage

An external resistor divider is used to set the output

voltage. The output voltage of the switching regulator

(VOUT) is determined by the following equation:



















OUT

Where VFB is 1.2V reference voltage.

Input Inductor Selection

The inductor value determines the ripple current. The

approximate ripple current and inductance value are

measured by the following equations:

ΔI

Where

ΔI = inductor ripple current

FSW = switch frequency

D = duty cycle, (VOUT- VIN)/ VOUT

Where

ΔI is inductor ripple current, FSW is switch

frequency and D is the duty cycle. Increasing the value

of inductance will reduce the output ripple current and

ripple voltage.

Input Capacitor Selection

Surfaces mount 4.7

μF or greater, X5R or X7R, ceramic

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