MIC2182 datasheet(25/40 Pages) MICROCHIP

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

2022 Microchip Technology Inc. and its subsidiaries

DS20006644A-page 25

MIC2182

The total output ripple is a combination of output ripple

voltages due to the ESR and the output capacitance.

The total ripple is calculated below:

EQUATION 5-27:

The voltage rating of capacitor should be twice the

output voltage for a tantalum and 20% greater for an

aluminum electrolytic or OS-CON.

The output capacitor RMS current is calculated below:

EQUATION 5-28:

The power dissipated in the output capacitor is:

EQUATION 5-29:

5.6

Input Capacitor Selection

The input capacitor should be selected for ripple

current rating and voltage rating. Tantalum input

capacitors may fail when subjected to high inrush

currents, caused by turning the input supply on.

Tantalum input capacitor voltage rating should be at

least twice the maximum input voltage to maximize

reliability. Aluminum electrolytic, OS-CON, and

multilayer polymer film capacitors can handle the

higher inrush currents without voltage derating.

The input voltage ripple will primarily depend on the

input capacitors ESR. The peak input current is equal

to the peak inductor current, so:

EQUATION 5-30:

The input capacitor must be rated for the input current

ripple. The RMS value of input capacitor current is

determined at the maximum output current. Assuming

the peak to peak inductor ripple current is low:

EQUATION 5-31:

The power dissipated in the input capacitor is:

EQUATION 5-32:

5.7

Voltage Setting Components

The MIC2182-3.3 and MIC2182-5.0 ICs contain

internal voltage dividers that set the output voltage. The

MIC2182 adjustable version requires two resistors to

set the output voltage as shown in Figure 5-2.

FIGURE 5-2:

Voltage Divider

Configuration.



VOUT

IL PP







8 COUT



fSW



--------------------------------------









IL PP







ESRCOUT





2

Where:

COUT = Output capacitance value

fSW = Switching frequency

ESRCOUT = ESR of output capacitor

ICOUT RMS





IL PP







------------------

PDISS COUT





ICOUT RMS





2 ESR

COUT





VIN IL PK





ESRCIN



Where:

ESRCIN = ESR of input capacitor.

ICIN RMS





IOUT MAX





1 D

–









PDISS CIN





ICIN RMS





2 ESR

CIN



Error

Amp

MIC2182 [adj.]

VREF

1.245V

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