TLC372M Datasheet, PDF (8/20 Pages) Texas Instruments – LIN CMOS DUAL DIFFERENTIAL COMPARATORS

TLC372
LinCMOS DUAL DIFFERENTIAL COMPARATORS
SLCS114D − NOVEMBER 1983 − REVISED APRIL 2004
PRINCIPLES OF OPERATION
LinCMOS process
The LinCMOS process is a Linear polysilicon-gate complementary-MOS process. Primarily designed for
single-supply applications, LinCMOS products facilitate the design of a wide range of high-performance
analog functions, from operational amplifiers to complex mixed-mode converters.
While digital designers are experienced with CMOS, MOS technologies are relatively new for analog designers.
This short guide is intended to answer the most frequently asked questions related to the quality and reliability
of LinCMOS products. Further questions should be directed to the nearest Texas Instruments field sales office.
electrostatic discharge
CMOS circuits are prone to gate oxide breakdown when exposed to high voltages even if the exposure is only
for very short periods of time. Electrostatic discharge (ESD) is one of the most common causes of damage to
CMOS devices. It can occur when a device is handled without proper consideration for environmental
electrostatic charges, e.g. during board assembly. If a circuit in which one amplifier from a dual operational
amplifier is being used and the unused pins are left open, high voltages tends to develop. If there is no provision
for ESD protection, these voltages may eventually punch through the gate oxide and cause the device to fail.
To prevent voltage buildup, each pin is protected by internal circuitry.
Standard ESD-protection circuits safely shunt the ESD current by providing a mechanism whereby one or more
transistors break down at voltages higher than the normal operating voltages but lower than the breakdown
voltage of the input gate. This type of protection scheme is limited by leakage currents which flow through the
shunting transistors during normal operation after an ESD voltage has occurred. Although these currents are
small, on the order of tens of nanoamps, CMOS amplifiers are often specified to draw input currents as low as
tens of picoamps.
To overcome this limitation, Texas Instruments design engineers developed the patented ESD-protection circuit
shown in Figure 4. This circuit can withstand several successive 1-kV ESD pulses, while reducing or eliminating
leakage currents that may be drawn through the input pins. A more detailed discussion of the operation of Texas
Instruments’s ESD- protection circuit is presented on the next page.
All input and output pins on LinCMOS and Advanced LinCMOS products have associated ESD-protection
circuitry that undergoes qualification testing to withstand 1000 V discharged from a 100-pF capacitor through
a 1500-Ω resistor (human body model) and 200 V from a 100-pF capacitor with no current-limiting resistor
(charged device model). These tests simulate both operator and machine handling of devices during normal
test and assembly operations.
VDD
R1
Input
To Protected Circuit
R2
Q1
Q2
D1
D2
D3
VSS
Figure 4. LinCMOS ESD-Protection Schematic
Advanced LinCMOS is a trademark of Texas Instruments Incorporated.
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