TLE2682 Datasheet, PDF (44/49 Pages) Texas Instruments – HIGH-SPEED JFET-INPUT DUAL OPERATIONAL AMPLIFIER WITH SWITCHED-CAPACITOR VOLTAGE CONVERTER

TLE2682
HIGHĆSPEED JFETĆINPUT DUAL OPERATIONAL AMPLIFIER
WITH SWITCHEDĆCAPACITOR VOLTAGE CONVERTER
SLOS127 − JUNE 1993
APPLICATION INFORMATION
pin functions (see functional block diagram − converter)
Supply voltage (V_IN) alternately charges C_IN to the input voltage when C_IN is switched in parallel with the input
supply and then transfers charge to C_OUT when C_IN is switched in parallel with C_OUT. Switching occurs at the
oscillator frequency. During the time that C_IN is charging, the peak supply current is approximately 2.2 times
the output current. During the time that C_IN is delivering a charge to C_OUT, the supply current drops to
approximately 0.2 times the output current. An input supply bypass capacitor supplies part of the peak input
current drawn by the TLE2682 switched-capacitor section and averages out the current drawn from the supply.
A minimum input supply bypass capacitor of 2 µF, preferably tantalum or some other low-ESR type, is
recommended. A larger capacitor is desirable in some cases. An example is when the actual input supply is
connected to the TLE2682 through long leads or when the pulse currents drawn by the TLE2682 might affect
other circuits through supply coupling.
In addition to being the output pin, V_OUT is tied to the substrate of the device. Special care must be taken in
TLE2682 circuits to avoid making V_OUT positive with respect to any of the other pins. For circuits with the output
load connected from V_{CC +} to V_OUT or from some external positive supply voltage to V_OUT, an external
Schottky diode must be added (see Figure 103). This diode prevents V_OUT from being pulled above the GND
during start up. A fast recovery diode such as IN4933 with low forward voltage (V_f ≈ 0.2 V) can be used.
VOUT
IN4933
COUT
+
Load
1
1 OUT
2
1 IN −
3
1 IN +
4
VCC _−
5
VOUT
6
VREF
7
OSC
8
VIN
16
VCC +
15
2 OUT
14
2 IN −
13
2 IN +
12
CAP −
11
GND
10
CAP +
9
FB/SD
VCC+ or External Supply Voltage
Figure 103. Circuit With Load Connected From V_CC to V_OUT
CIN
+
The voltage reference (V_REF) output provides a 2.5-V reference point for use in TLE2682-based regulator
circuits. The temperature coefficient (TC) of the reference voltage has been adjusted so that the TC of the
regulated output voltage is near zero. As seen in the typical performance curves, this requires the reference
output to have a positive TC. This nonzero drift is necessary to offset a drift term inherent in the internal reference
divider and comparator network tied to the feedback pin. The overall result of these drift terms is a regulated
output that has a slight positive TC at output voltages below 5 V and a slight negative TC at output voltages
above 5 V. For regulator feedback networks, reference output current should be limited to approximately 60 µA.
V_REF draws approximately 100 µA when shorted to ground and does not affect the internal reference/regulator.
This pin can also be used as a pullup for TLE2682 circuits that require synchronization.
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