TLV172IDCKT.B datasheet(17/49 Pages) TI2

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Power-Supply

ESD Cell

2.5

NŸ

2.5

NŸ

IN+

TVS

VIN

±VS

TVS

+VS

TLV172, TLV2172, TLV4172

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SBOS784C – NOVEMBER 2016 – REVISED JANUARY 2019

Product Folder Links: TLV172 TLV2172 TLV4172

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Feature Description (continued)

Figure 26. Equivalent Internal ESD Circuitry Relative to a Typical Circuit Application

An ESD event produces a short-duration, high-voltage pulse that is transformed into a short-duration, high-

current pulse when discharging through a semiconductor device. The ESD protection circuits are designed to

provide a current path around the operational amplifier core to prevent damage. The energy absorbed by the

protection circuitry is then dissipated as heat.

When an ESD voltage develops across two or more amplifier device pins, current flows through one or more

steering diodes. Depending on the path that the current takes, the absorption device can activate. The absorption

device has a trigger, or threshold voltage, that is above the normal operating voltage of the TLVx172 but below

the device breakdown voltage level. When this threshold is exceeded, the absorption device quickly activates

and clamps the voltage across the supply rails to a safe level.

When the operational amplifier connects into a circuit, as shown in Figure 26, the ESD protection components

are intended to remain inactive and do not become involved in the application circuit operation. However,

circumstances can arise where an applied voltage exceeds the operating voltage range of a given pin. If this

condition occurs, there is a risk that some internal ESD protection circuits can turn on and conduct current. Any

such current flow occurs through steering-diode paths and rarely involves the absorption device.

Figure 26 shows a specific example where the input voltage (VIN) exceeds the positive supply voltage (V+) by

500 mV or more. Much of what happens in the circuit depends on the supply characteristics. If V+ can sink the

current, then one of the upper input steering diodes conducts and directs current to V+. Excessively high current

levels can flow with increasingly higher VIN. As a result, the data sheet specifications recommend that

applications limit the input current to 10 mA.

If the supply is not capable of sinking the current, VIN can begin sourcing current to the operational amplifier and

then take over as the source of positive supply voltage. The danger in this case is that the voltage can rise to

levels that exceed the operational amplifier absolute maximum ratings.

Another common question involves what happens to the amplifier if an input signal is applied to the input when

the power supplies (V+ or V–) are at 0 V. Again, this question depends on the supply characteristic when at 0 V,

or at a level below the input signal amplitude. If the supplies appear as high impedance, then the input source

supplies the operational amplifier current through the current-steering diodes. This state is not a normal bias

condition; most likely, the amplifier does not operate normally. If the supplies are low impedance, then the current

through the steering diodes can become quite high. The current level depends on the ability of the input source

to deliver current and any resistance in the input path.

TLV172IDCKT.B Datasheet(PDF) 17 Page - Texas Instruments

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