TLV914X datasheet(24/54 Pages) TI1

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

current pulse while 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 terminals, 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 TLV914x

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 6-6), 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 terminal. 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 6-6 shows a specific example where the input voltage (VIN) exceeds the positive supply voltage (+VS)

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

sink the current, one of the upper input steering diodes conducts and directs current to +VS. 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 10mA.

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 while

the power supplies +VS or –VS are at 0V. Again, this question depends on the supply characteristic while at 0V,

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 will 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.

If there is any uncertainty about the ability of the supply to absorb this current, add external Zener diodes to

the supply terminals; see Figure 6-6. Select the Zener voltage so that the diode does not turn on during normal

operation. However, the Zener voltage must be low enough so that the Zener diode conducts if the supply

terminal begins to rise above the safe-operating, supply-voltage level.

The TLV914x input terminals are protected from excessive differential voltage with back-to-back diodes; see

Figure 6-6. In most circuit applications, the input protection circuitry has no effect. However, in low-gain or G =

1 circuits, fast-ramping input signals can forward-bias these diodes because the output of the amplifier cannot

respond rapidly enough to the input ramp. If the input signal is fast enough to create this forward-bias condition,

limit the input signal current to 10mA or less. If the input signal current is not inherently limited, an input

series resistor can be used to limit the input signal current. This input series resistor degrades the low-noise

performance of the TLV914x. Figure 6-6 shows an example configuration that implements a current-limiting

feedback resistor.

6.3.6 Overload Recovery

Overload recovery is defined as the time required for the op amp output to recover from a saturated state to

a linear state. The output devices of the op amp enter a saturation region when the output voltage exceeds

the rated operating voltage, either due to the high input voltage or the high gain. After the device enters the

saturation region, the charge carriers in the output devices require time to return back to the linear state. After

the charge carriers return back to the linear state, the device begins to slew at the specified slew rate. Thus, the

propagation delay in case of an overload condition is the sum of the overload recovery time and the slew time.

The overload recovery time for the TLV914x is approximately 400ns.

TLV9141, TLV9142, TLV9144

SBOSAM4 – DECEMBER 2024

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