CAT661

10

Doc. No. 5003, Rev. J

CAPACITOR SUPPLIERS

The following manufacturers supply low-ESR capacitors:

Manufacturer

Capacitor Type

Phone

WEB

Email

Comments

AVX/Kyocera

TPS/TPS3

843-448-9411

www.avxcorp.com

avx@avxcorp.com

Tantalum

Vishay/Sprague 595

402-563-6866

www.vishay.com

—

Aluminum

Sanyo

MV-AX, UGX

619-661-6835

www.sanyo.com

Svcsales@sanyo.com Aluminum

Nichicon

F55

847-843-7500

www.nichicon-us.com

—

Tantalum

HC/HD

Aluminum

The effective output impedance of a CAT661 circuit is

approximately:

Rcircuit

≈ Rout 661 + (4 x ESRC1) + ESRC2

VOLTAGE INVERSION POSITIVE-TO-NEGATIVE

The CAT661 easily provides a negative supply voltage

from a positive supply in the system. Figure 8 shows a

typical circuit. The LV pin may be left floating for positive

input voltages at or above 3.3V.

Figure 8: Voltage Inverter

CONTROLLING LOSS IN CAT661 APPLICATIONS

There are three primary sources of voltage loss:

1.

Output resistance

VLOSS = ILOAD x ROUT, where ROUT is the

CAT661 output resistance and ILOAD is the

load current.

2.

Charge pump (C1) capacitor ESR:

VLOSSC1

4 x ESRC1 x ILOAD, where

ESRC1 is the ESR of capacitor C1.

3.

Output or reservoir (C2) capacitor ESR:

VLOSSC2 = ESRC2 x ILOAD, where ESRC2

is the ESR of capacitor C2.

Increasing the value of C2 and/or decreasing its ESR will

reduce noise and ripple.

≈

+

VOUT = -VIN

C2

1

2

3

4

8

7

6

5

CAT661

NC

+

C1

VIN

1.5V to 5.5V

BOOST/FC

CAP+

GND

CAP-

V+

OSC

LV

OUT

Capacitor manufacturers continually introduce new series

and offer different package styles. It is recommended

that before a design is finalized capacitor manufacturers

should be surveyed for their latest product offerings.

TYPICAL APPLICATIONS