© 2005 Microchip Technology Inc.

DS21486C-page 5

TCM680

3.0

PIN DESCRIPTION

The descriptions of the pins are listed in Table 3-1.

TABLE 3-1:

PIN FUNCTION TABLE

3.1

Negative connection for the charge pump capacitor

(flying capacitor) used to transfer charge from the input

source to a second charge pump capacitor. This

charge pump capacitor is used to double the input volt-

age and store the charge in the second charge pump

capacitor.

It is recommended that a low ESR (equivalent series

resistance) capacitor be used. Additionally, larger

values will lower the output resistance.

3.2

Second Charge Pump Capacitor

Positive connection for the second charge pump

capacitor (flying capacitor) used to transfer charge from

the first charge pump capacitor to the output.

It is recommended that a low ESR (equivalent series

resistance) capacitor be used. Additionally, larger

values will lower the output resistance.

3.3

Second Charge Pump Capacitor

Negative connection for the second charge pump

capacitor (flying capacitor) used to transfer charge from

the first charge pump capacitor to the output. Proper

orientation is imperative when using a polarized

capacitor.

3.4

Negative connection for the negative charge pump out-

put capacitor. The negative charge pump output capac-

itor supplies the output load during the first, third and

fourth phases of the switching cycle. During the second

phase of the switching cycle, charge is restored to the

negative charge pump output capacitor. The negative

output voltage magnitude is approximately twice the

input voltage.

It is recommended that a low ESR (equivalent series

resistance) capacitor be used. Additionally, larger

values will lower the output ripple.

3.5

Ground (GND)

Input zero volt reference.

3.6

Positive power supply input voltage connection. It is

recommended that a low ESR (equivalent series resis-

tance) capacitor be used to bypass the power supply

input to ground (GND).

3.7

Positive connection for the charge pump capacitor (fly-

ing capacitor) used to transfer charge from the input

source to a second charge pump capacitor. Proper

orientation is imperative when using a polarized

capacitor.

3.8

Positive connection for the positive charge pump out-

put capacitor. The positive charge pump output capac-

itor supplies the output load during the first, second and

third phases of the switching cycle. During the fourth

phase of the switching cycle, charge is restored to the

positive charge pump output capacitor. The positive

output voltage magnitude is approximately twice the

input voltage.

It is recommended that a low ESR (equivalent series

resistance) capacitor be used. Additionally, larger

values will lower the output ripple.

Pin No.

(8-Pin PDIP,

SOIC)

Symbol

Description

-

Input. First charge pump

capacitor. Negative

connection

+

Input. Second charge pump

capacitor. Positive

connection.

-

Input. Second charge pump

capacitor. Negative

connection.

-

Output. Negative Output

voltage

5

GND

Input. Ground connection.

Input. Power supply.

+

Input. First charge pump

capacitor. Positive

connection.

+

Output. Positive Output

Voltage.