Datasheet

TLV2322, TLV2322Y, TLV2324, TLV2324Y
LinCMOS LOW-VOLTAGE LOW-POWER
OPERATIONAL AMPLIFIERS
SLOS187 – FEBRUARY 1997
27
POST OFFICE BOX 655303 DALLAS, TEXAS 75265
APPLICATION INFORMATION
by more than 300 mV. Care should be exercised when using capacitive coupling on pulse generators. Supply
transients should be shunted by the use of decoupling capacitors (0.1 µF typical) located across the supply rails
as close to the device as possible.
The current path established if latch-up occurs is usually between the positive supply rail and ground and can
be triggered by surges on the supply lines and/or voltages on either the output or inputs that exceed the supply
voltage. Once latch-up occurs, the current flow is limited only by the impedance of the power supply and the
forward resistance of the parasitic thyristor and usually results in the destruction of the device. The chance of
latch-up occurring increases with increasing temperature and supply voltages.
output characteristics
The output stage of the TLV232x is designed to
sink and source relatively high amounts of current
(see Typical Characteristics). If the output is
subjected to a short-circuit condition, this
high-current capability can cause device damage
under certain conditions. Output current capability
increases with supply voltage.
Although the TLV232x possesses excellent
high-level output voltage and current capability,
methods are available for boosting this capability,
if needed. The simplest method involves the use
of a pullup resistor (R
P
) connected from the output
to the positive supply rail (see Figure 44). There
are two disadvantages to the use of this circuit.
First, the NMOS pulldown transistor N4 (see
equivalent schematic) must sink a comparatively
large amount of current. In this circuit, N4 behaves
like a linear resistor with an on resistance between
approximately 60 and 180 depending on how
hard the operational amplifier input is driven. With
very low values of R
P
, a voltage offset from 0 V at
the output occurs. Secondly, pullup resistor R
P
acts as a drain load to N4 and the gain of the
operational amplifier is reduced at output voltage
levels where N5 is not supplying the output
current.
All operating characteristics of the TLV232x are
measured using a 20-pF load. The device drives
higher capacitive loads; however, as output load capacitance increases, the resulting response pole occurs at
lower frequencies, thereby causing ringing, peaking, or even oscillation (see Figure 45 and Figure 46). In many
cases, adding some compensation in the form of a series resistor in the feedback loop alleviates the problem.
+
V
O
C
L
V
I
2.5 V
T
A
= 25°C
f = 1 kHz
V
I(PP)
= 1 V
2.5 V
+
R
P
V
DD
V
O
I
F
I
L
I
P
I
P
= Pullup Current
Required by the
Operational Amplifier
(typically 500 µA)
V
O
V
DD
R
P
I
P
I
F
I
L
R
L
V
I
R1
R2
Figure 44. Resistive Pullup to Increase V
OH
Figure 45. Test Circuit for Output Characteristics