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(

)

CC

CC

DD

boost

CC

I

V

V

C = 2

V

f

V

´

-

´

D

´

´

(4)

(

)

CC

CC

DD

boost

CC

I

V

V

C =

V

f

V

´

-

D

´

´

(5)

TPA2013D1

SLOS520 – AUGUST 2007

TPA2013D1 CAPACITOR EQUATIONS

The value of the boost capacitor is determined by the minimum value of working capacitance required for stability

10

μF. Do not use any component with a working capacitance less than 10 μF.

For X5R or X7R ceramic capacitors, Equation 4 shows the relationship between the boost capacitance, C, to

respectively). Insert the maximum allowed ripple voltage into Equation 4 to solve for C. A factor of 2 is included

to implement the rules and specifications listed earlier.

For aluminum or tantalum capacitors, Equation 5 shows the relationship between he boost capacitance, C, to

respectively). Insert the maximum allowed ripple voltage into Equation 5 to solve for C. Solve this equation

assuming ESR is zero.

Capacitance of aluminum and tantalum capacitors is normally not sensitive to applied voltage so there is no

factor of 2 included in Equation 5. However, the ESR in aluminum and tantalum capacitors can be significant.

Choose an aluminum or tantalum capacitor with ESR around 30 m

Ω. For best perfornamce using of tantalum

capacitor, use at least a 10 V rating. Note that tantalum capacitors must generally be used at voltages of half

their ratings or less.

16

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