Datasheet

LM7332
www.ti.com SNOSAV4A –APRIL 2008–REVISED MARCH 2013
APPLICATION INFORMATION
ADVANTAGES OF THE LM7332
Wide Operating Voltage Range
The LM7332 has an operating voltage from 2.5V to 32V which makes it suitable for industrial and automotive
applications.
RRIO with 100 mA Output Current
The LM7332 takes advantages of Texas Instruments' VIP3 process which enables high current driving from the
rails. Rail-to-rail output swing provides the maximum possible output dynamic range. The LM7332 eliminates the
need to use extra transistors when driving large capacitive loads, therefore reducing the application cost and
space.
-40°C to 125°C Operating Temperature Range
The LM7332 has an operating temperature ranging from -40°C to 125°C, which is Automotive Grade 1, and also
meets most industrial requirements.
SOIC and VSSOP Packages
The LM7332 are offered in both the standard SOIC package and the space saving VSSOP package. Please
refer to the Physical Dimensions on page 17 for details.
OUTPUT VOLTAGE SWING CLOSE TO V
−
The LM7332’s output stage design allows voltage swings to within millivolts of either supply rail for maximum
flexibility and improved useful range. Because of this design architecture, with output approaching either supply
rail, the output transistor Collector-Base junction reverse bias will decrease. With output less than a V
be
from
either rail, the corresponding output transistor operates near saturation. In this mode of operation, the transistor
will exhibit higher junction capacitance and lower f
t
which will reduce phase margin. With the Noise Gain (NG = 1
+ R
F
/R
G
, R
F
and R
G
are external gain setting resistors) of 2 or higher, there is sufficient phase margin that this
reduction in phase margin is of no consequence. However, with lower Noise Gain (<2) and with less than 150
mV to the supply rail, if the output loading is light, the phase margin reduction could result in unwanted
oscillations.
In the case of the LM7332, due to inherent architectural specifics, the oscillation occurs only with respect to the
output transistor at V
−
when output swings to within 150 mV of V
−
. However, if this output transistor's collector
current is larger than its idle value of a few microamps, the phase margin loss becomes insignificant. In this case,
300 μA is the required output transistor's collector current to remedy this situation. Therefore, when all the
aforementioned critical conditions are present at the same time (NG < 2, V
OUT
< 150 mV from supply rails, &
output load is light) it is possible to ensure stability by adding a load resistor to the output to provide the output
transistor the necessary minimum collector current (300 μA).
For 12V (or ±6V) operation, for example, add a 39 kΩ resistor from the output to V
+
to cause 300 µA output
sinking current and ensure stability. This is equivalent to about 15% increase in total quiescent power dissipation.
DRIVING CAPACITIVE LOADS
The LM7332 is specifically designed to drive unlimited capacitive loads without oscillations. In addition, the
output current handling capability of the device allows for good slewing characteristics even with large capacitive
loads as shown in Figure 49. The combination of these features is ideal for applications such as TFT flat panel
buffers, A/D converter input amplifiers and power transistor driver.
However, as in most op amps, addition of a series isolation resistor between the op amp and the capacitive load
improves the settling and overshoot performance.
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