Application Notes

North America (USA): 1-888-41-ASTEC

Europe (UK): 44(1384)842-211

Asia (HK): 852-2437-9662

Table 2-1: Input/Output Capacitors

ATH22T033/T05: Capacitor Recommendations

Input Capacitor

The recommended input capacitor(s) is determined by

minimum ripple current rating.

Ripple current and <100 m

Ω equivalent series resistance

(ESR) values are the major considerations, along with

temperature, when designing with different types of

capacitors. Tantalum capacitors have a recommended

minimum voltage rating of 2

× (the maximum DC voltage

+ AC ripple). This is standard practice for tantalum

capacitors to insure reliability.

Ceramic Capacitors

Ceramic capacitors may be substituted for electrolytic

types using the minimum capacitance, for improved

ripple reduction on the input bus.

Output Capacitors (Optional)

The recommended ESR of the capacitors is equal to or

less than 150 m

Ω. Electrolytic capacitors have marginal

ripple performance at frequencies greater than 400 kHz

but excellent low frequency transient response. Above

the ripple frequency, ceramic capacitors are necessary to

improve the transient response and reduce any high

frequency noise components apparent during higher

current excursions. Preferred low ESR type capacitor part

numbers are identified in Table 2-1.

Tantalum Capacitors

Tantalum type capacitors can be used for the output, but

only the AVX TPS, Sprague 593D/594/595or Kemet

T495/T510 series. These capacitors are recommended

over many other tantalum types due to their higher rated

surge, power dissipation, and ripple current capability.

As a caution the TAJ series by AVX is not recommended.

This series has considerably higher ESR, reduced power

dissipation, and lower ripple current capability. The TAJ

series is less reliable than the AVX TPS series when

determining power dissipation capability. Tantalum,

ceramic, or Os-con types are recommended for applica-

tions where ambient temperatures fall below 0 °C.

Capacitor Table

Table 2-1 identifies the characteristics of capacitors from a

number of vendors with acceptable ESR and ripple current

(rms) ratings. The number of capacitors required at both

the input and output buses is identified for each capacitor

type.

This is not an extensive capacitor list. Capacitors from other

vendors are available with comparable specifications. Those

listed are for guidance. The RMS ripple current rating and

ESR (at 100kHz) are critical parameters necessary to insure

both optimum regulator performance and long capacitor life.

/

r

o

d

n

e

V

r

o

t

i

c

a

p

a

C

s

e

i

r

e

S

s

c

i

t

s

i

r

e

t

c

a

r

a

h

C

r

o

t

i

c

a

p

a

Cy

t

i

t

n

a

u

Q

g

n

i

k

r

o

W

e

g

a

t

l

o

V

)

F

µ

(

e

u

l

a

Vt

n

e

l

a

v

i

u

q

E

)

R

S

E

(

e

c

n

a

t

s

i

s

e

R

s

e

i

r

e

S

m

u

m

i

x

a

M

C

°

5

0

1

e

l

p

p

i

R

)

s

m

r

I

(

t

n

e

r

r

u

C

l

a

c

i

s

y

h

P

)

m

m

(

e

z

i

S

t

u

p

n

I

s

u

B

t

u

p

t

u

O

s

u

B

r

e

b

m

u

N

t

r

a

P

r

o

d

n

e

V

c

i

n

o

s

a

n

a

P

)

l

a

i

d

a

R

(

C

F

K

F)

.

t

M

e

c

a

f

r

u

S

(

V

0

1

V

0

1

V

5

2

V

0

1

0

6

5

0

0

0

1

0

0

0

1

0

0

0

1

0

9

0

.

0

Ω

8

6

0

.

0

Ω

0

6

0

0

Ω

0

8

0

.

0

Ω

A

m

5

5

7

A

m

0

5

0

1

A

m

0

0

1

1

A

m

0

5

8

0

1

× 5

.

2

1

0

1

× 6

1

5

.

2

1

× 5

.

3

1

0

1

× 2

.

0

1

2

1

1

1

1

1

1

1

1

6

5

A

1

C

F

U

E

E

2

0

1

A

1

C

F

U

E

E

Q

2

0

1

E

1

K

F

V

E

E

P

2

0

1

A

1

K

F

V

E

E

n

o

c

-

i

m

e

h

C

d

e

t

i

n

U

)

.

t

M

e

c

a

f

r

u

S

(

A

X

P

X

F

s

e

i

r

e

S

Z

X

L

V

3

.

6

V

3

.

6

V

0

1

V

0

1

0

7

4

0

0

0

1

0

8

6

0

0

0

1

0

2

0

.

0

Ω

3

1

0

.

0

Ω

0

9

0

.

0

Ω

8

6

0

.

0

Ω

A

m

0

3

1

4

A

m

5

3

9

4

A

m

0

6

7

A

m

0

5

0

1

0

1

× 7

.

7

0

1

× 5

.

0

1

0

1

× 5

.

2

1

0

1

× 6

1

)

1

(

2

1

2

1

1

1

1

1

P

T

0

8

J

M

1

7

4

C

V

3

.

6

A

X

P

M

0

0

0

1

X

F

6

L

L

2

1

X

0

1

M

1

8

6

B

V

0

1

Z

X

L

L

L

6

1

X

0

1

M

2

0

1

B

V

0

1

Z

X

L

n

o

c

i

h

c

i

N

s

e

i

r

e

S

M

P

V

3

.

6

V

0

1

V

6

1

0

0

0

1

0

0

0

1

0

0

0

1

3

5

0

.

0

Ω

5

6

0

.

0

Ω

5

5

0

.

0

Ω

A

m

0

3

0

1

A

m

0

6

0

1

A

m

0

0

4

4

5

.

2

1

x

0

1

6

1

× 5

1

0

1

× 0

1

1

1

1

1

1

1

R

P

M

2

0

1

J

0

D

H

U

6

H

P

M

2

0

1

A

1

M

P

U

6

H

H

M

2

0

1

C

1

M

P

U

:

n

o

c

-

s

O

-

o

y

n

a

S

P

S

)

.

t

M

e

c

a

f

r

u

S

(

P

V

S

V

0

1

V

0

1

0

7

4

0

6

5

5

1

0

.

0

Ω

3

1

0

.

0

Ω

A

m

0

0

5

4

>

A

m

0

0

2

5

>

0

1

× 5

.

0

1

0

1

× 7

.

2

1

)

1

(

2

2

1

1

M

0

7

4

P

S

0

1

M

0

6

5

P

V

S

0

1

m

u

l

a

t

n

a

T

X

V

A

)

.

t

M

e

c

a

f

r

u

S

(

S

P

T

V

0

1

V

0

1

0

7

4

0

7

4

5

4

0

.

0

Ω

0

6

0

.

0

Ω

A

m

3

2

7

1

A

m

6

2

8

1

L

3

.

7

× W

7

.

5

× H

1

.

4

)

1

(

2

)

1

(

2

1

1

5

4

0

0

R

0

1

0

M

7

7

4

E

S

P

T

0

6

0

0

R

0

1

0

M

7

7

4

V

S

P

T

r

e

m

y

l

o

P

t

e

m

e

K

m

u

l

a

t

n

a

T

s

e

i

r

e

S

0

3

5

T

/

0

2

5

T

)

.

t

M

e

c

a

f

r

u

S

(

V

0

1

V

0

1

0

3

3

0

3

3

0

4

0

.

0

Ω

5

1

0

.

0

Ω

A

m

0

0

8

1

A

m

0

0

8

3

>

W

3

.

4

× L

3

.

7

× H

0

.

4

3

3

1

1

S

A

0

1

0

M

7

3

3

X

0

2

5

T

S

A

0

1

0

M

7

3

3

X

0

3

5

T

m

u

l

a

t

n

a

T

e

u

g

a

r

p

S

s

e

i

r

e

S

D

5

9

5

)

.

t

M

e

c

a

f

r

u

S

(

V

0

10

7

40

0

1

.

0

Ω

A

m

0

4

4

1L

2

.

7

× W

6

× H

1

.

4

)

1

(

21

T

2

R

0

1

0

0

X

7

7

4

D

5

9

5

ATH22T033 & ATH22T05 Series

(1) Total capacitance of 940 µF is acceptable based on the combined ripple current rating.