Datasheet

Figure 43. Resistive Pullup to Increase V
OH
–
+
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
–
+
V
O
C
L
V
I
2.5 V
T
A
= 25°C
f = 1 kHz
V
I(PP)
= 1 V
–2.5 V
Figure 44. Test Circuit for Output Characteristics
TLV2332, TLV2332Y, TLV2334, TLV2334Y
LinCMOS LOW-VOLTAGE MEDIUM-POWER
OPERATIONAL AMPLIFIERS
SLOS189 – FEBRUARY 1997
27
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
latch-up
Because CMOS devices are susceptible to latch-up due to their inherent parasitic thyristors, the TLV233x inputs
and outputs are designed to withstand –100-mA surge currents without sustaining latch-up; however,
techniques should be used to reduce the chance of latch-up whenever possible. Internal-protection diodes
should not by design be forward biased. Applied input and output voltage should not exceed the supply voltage
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 TLV233x 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 TLV233x 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 43). 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 Ω and 180 Ω, 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 TLV233x 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 44 and Figure 45). In many cases,
adding some compensation in the form of a series resistor in the feedback loop alleviates the problem.