TLE2662

DUAL

µPOWER JFET-INPUT OPERATIONAL AMPLIFIER

WITH SWITCHED-CAPACITOR VOLTAGE CONVERTER

SLOS118B – DECEMBER 1992 – REVISED AUGUST 1994

25

POST OFFICE BOX 655303

APPLICATION INFORMATION

switched-capacitor section (continued)

The TLE2662, with its high-output-drive amplifiers and switched-capacitor voltage converter, readily lends itself

to applications like headphone drivers where large signal swing into heavy loads is paramount. Another

application is analog-to-digital interfacing when only a single rail is available to the system, but maximization

of the ADC dynamic range is key. See Figure 48 for the functional block diagram of the switched-capacitor block.

typical application

In its most basic configuration, the TLE2662 switched-capacitor section is used as a voltage inverter to provide

the negative rail for the amplifiers in a single-supply system. As shown in Figure 49, the positive 5-V supply is

external components (excluding the resistors used with the amplifiers) are necessary: the storage capacitors,

CIN and COUT, and a fast-recovery Schottky diode to clamp SCOUT during start up. The diode is necessary

because the amplifiers present a load referenced to the positive rail and tends to pull SCOUT above ground,

which can cause the device to fail to start up (see pin functions section in APPLICATION INFORMATION). As

shown in Figure 50, one amplifier is shown driving a resistive load; the other is interfacing to an analog-to-digital

converter (ADC).

Filter

Shutdown

RL

RF

RF

To ADC

5 V

RF

RIN

+

+

COUT

1

2

3

4

5

6

7

8

1OUT

1IN –

1IN +

VCC –

SCOUT

SCREF

OSC

SCIN

16

15

14

13

12

11

10

9

VCC +

2OUT

2IN –

2IN +

CAP –

GND

CAP +

FB/SD

CIN

Signal

From

Preamplifier

Signal

From

Transducer

1N4933

Figure 49. Switched-Capacitor Block Supplying Negative Rail for Amplifiers