 2002 Microchip Technology Inc.

DS21465B-page 5

TC7660

3.0

PIN DESCRIPTIONS

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

TABLE 3-1:

PIN FUNCTION TABLE

3.1

Positive connection for the charge pump capacitor, or

flying capacitor, used to transfer charge from the input

source to the output. In the voltage-inverting configura-

tion, the charge pump capacitor is charged to the input

voltage during the first half of the switching cycle. Dur-

ing the second half of the switching cycle, the charge

pump capacitor is inverted and charge is transferred to

the output capacitor and load.

It is recommended that a low ESR (equivalent series

resistance) capacitor be used. Additionally, larger

values will lower the output resistance.

3.2

Ground (GND)

Input and output zero volt reference.

3.3

Negative connection for the charge pump capacitor, or

flying capacitor, used to transfer charge from the input

to the output. Proper orientation is imperative when

using a polarized capacitor.

3.4

Negative connection for the charge pump output

capacitor. In the voltage-inverting configuration, the

charge pump output capacitor supplies the output load

during the first half of the switching cycle. During the

second half of the switching cycle, charge is restored to

the charge pump output capacitor.

It is recommended that a low ESR (equivalent series

resistance) capacitor be used. Additionally, larger

values will lower the output ripple.

3.5

Low Voltage Pin (LV)

The low voltage pin ensures proper operation of the

internal oscillator for input voltages below 3.5V. The low

voltage pin should be connected to ground (GND) for

input voltages below 3.5V. Otherwise, the low voltage

pin should be allowed to float.

3.6

Oscillator Control Input (OSC)

The oscillator control input can be utilized to slow down

or speed up the operation of the TC7660. Refer to

Section 5.4,

“Changing

the

TC7660

Oscillator

Frequency”, for details on altering the oscillator

frequency.

3.7

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).

Pin No.

Symbol

Description

1

NC

No connection

Charge pump capacitor positive terminal

3

GND

Ground terminal

Charge pump capacitor negative terminal

Output voltage

6

LV

Low voltage pin. Connect to GND for V+ < 3.5V

7

OSC

Oscillator control input. Bypass with an external capacitor to slow the oscillator

Power supply positive voltage input