8

Date: 5/25/04

SP6680 High Efficiency Buck/Boost Charge Pump Regulator

© Copyright 2004 Sipex Corporation

Table 3. Output Resistance vs Output Capacitance

All Ceramic Capacitors ESR < 0.05ohm

Cin, CF1, CF2 = 2.2uF, Vin = 3.85V, Iout = 5mA, CLK = 32kHz

Cout (uF)

SP6680 Rout (ohms)

0.47

57

128

2.2

18

4.7

13

10

11

22

10

Table 4. Output Resistance vs Pump Capacitance

All Ceramic Capacitors ESR < 0.05ohm

Cin, Cout = 2.2uF, Vin = 3.85V, Iout = 5mA, CLK = 32kHz

CF1, CF2 (uF)

SP6680 Rout (ohms)

0.47

39

124

2.2

18

4.7

15

10

14

22

13

#

E

N

O

H

P

E

L

E

T

/

R

E

R

U

T

C

A

F

U

N

A

MR

E

B

M

U

N

T

R

A

P

/

E

C

N

A

T

I

C

A

P

A

C

E

G

A

T

L

O

V

R

S

E

X

A

M

z

H

k

0

0

1

@

R

O

T

I

C

A

P

A

C

E

P

Y

T

/

E

Z

I

S

0

0

1

6

-

3

0

8

-

7

4

8

/

K

D

TK

5

2

2

A

1

R

5

X

2

1

0

2

C2

.

2 µ

V

0

1

/

F0

3

0

.

0

Ω

R

5

X

/

5

0

8

0

0

0

1

6

-

3

0

8

-

7

4

8

/

K

D

TK

5

7

4

C

1

R

5

X

6

1

2

3

C7

.

4 µ

V

0

1

/

F0

2

0

.

0

Ω

R

5

X

/

6

0

2

1

1

1

4

9

-

8

4

4

-

3

4

8

/

X

V

AK

5

2

2

C

Z

6

0

2

12

.

2 µ

V

0

1

/

F0

3

0

.

0

Ω

R

7

X

/

6

0

2

1

8

8

8

0

-

5

2

9

-

7

4

8

/

n

e

d

u

Y

o

y

i

a

TG

M

5

2

2

J

B

2

1

2

K

M

L2

.

2 µ

V

0

1

/

F0

3

0

.

0

Ω

R

5

X

/

5

0

8

0

8

8

8

0

-

5

2

9

-

7

4

8

/

n

e

d

u

Y

o

y

i

a

TL

M

5

7

4

J

B

6

1

3

K

M

L7

.

4 µ

V

0

1

/

F0

2

0

.

0

Ω

R

7

X

/

6

0

2

1

Board Layout

PC board layout is an important design consideration to mitigate switching current effects. High

frequency operation makes PC layout important for minimizing ground bounc and noise. Components

should be place as close to the IC as possible with connections made through short, low impedance

traces. To maximize output ripple voltage, use a ground plane and solder the IC's GND pin directly to

the ground plane.

Output Resistance with Various Output and Pump Capacitors

From Tables 3 & 4 it can be seen that increasing output capacitance alone reduces the output resistance

more than increasing pump capacitance. This offers the advantage of increasing one capacitor versus

two capacitors in the case for the pump capacitance.

Figure 2. Suggested Low ESR Cermic Surface Mount Capacitors.