TLE2662 Datasheet, PDF (25/40 Pages) Texas Instruments – DUAL uPOWER JFET-INPUT OPERATIONAL AMPLIFIER WITH SWITCHED-CAPACITOR VOLTAGE CONVERTER

TLE2662
DUAL µPOWER JFET-INPUT OPERATIONAL AMPLIFIER
WITH SWITCHED-CAPACITOR VOLTAGE CONVERTER
SLOS118B – DECEMBER 1992 – REVISED AUGUST 1994
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
connected to both V_{CC +} and SCIN. V_{CC –} is connected to the output of the charge pump, SCOUT. Only three
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).
RL
5V
To ADC
RF
Signal
RF
From
Preamplifier
Filter
COUT
1N4933
+
1
1OUT
2
1IN –
3
1IN +
4
VCC _–
5
SCOUT
6
SCREF
7
OSC
16
VCC ₊
15
2OUT
14
2IN –
13
2IN +
12
CAP –
11
GND
10
CAP +
RF
CIN
+
RIN
Signal
From
Transducer
8
SCIN
9
FB/SD
Shutdown
Figure 49. Switched-Capacitor Block Supplying Negative Rail for Amplifiers
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