OPA2196: Input tolerant spec

The absolute maximum ratings show that the input voltages must no go more than 0.5 V beyond the rails; this implies that there are diodes. And there is a 10 mA limit for the input pin current; this is the diode current (the input bias current during normal operation is much lower).

Thank you Clemens,

Hi T.C.,

As Clemens have mentioned, if the op-amps inputs will be exposed to a voltage above (V+) + 0.5V or a voltage below (V-) - 0.5V, the current needs to be limited to less than ±10mA, using a series resistor or external clamp.  Also, if the differential input voltage or voltage across the IN+ - IN- terminals will exceed (V+) - (V-) +0.2V, the current must be limited to less than ±10mA.

If in the application, the device will be submitted to conditions that exceed the absolute maximum ratings, a common practice is to use external clamping circuit.  This is typically accomplished using series resistors to limit current or a combination of series resistors, external Schottky diodes on the op-amp input to stir the current, and TVS diodes on the op-amp supplies.

Below is a quick example, a clamp circuit is designed to provide input protection for a common-mode  ±40-V continuous overvoltage fault. The Schottky diodes, used here on the op amp inputs, have a metal semiconductor junction that offers a lower forward voltage drop than the silicon junction diodes, such as those internal diodes used for ESD protection in the op amp. The Figure below details how this attribute of the external protection clamp circuit works in conjunction with those internal ESD diodes. The current during the ±40-V fault is limited to 20 mA using the 1.24-kΩ, 1/2-W R_LIMIT resistor, as shown in Figure below.

In this example, the BAS40 is a small-signal Schottky diode with a forward voltage close to ~380 mV at 1 mA. In comparison, the internal ESD structure has a forward voltage somewhere around ~550 mV at the same forward current. Therefore, the Schottky diodes turn on before the amplifier’s internal ESD diodes, and most of the in-rush current flows through the external clamp. The internal ESD structure can only withstand 10 mA, while the external Schottky diode can handle forward continuous currents up to 200 mA, providing strong protection.

The transient voltage suppression (TVS) diodes are used to clamp the power rails, sinking the clamp circuit current to keep the supplies below the op amp’s ±20-V absolute supply rating. TVS diodes are like Zener diodes, but designed for fast, large transient power dissipation. The SMF12A shown is a unidirectional TVS with a reverse standoff voltage of 12 V, a breakdown voltage of 14.7 V and a maximum clamping voltage of 19.9 V. 

Please review the TI Precision Lab Session explaining overstress or EOS protection:

https://www.ti.com/video/series/precision-labs/ti-precision-labs-op-amps.html

To find the session on EOS protection, look into "Topics" and browse the bottom of the page, you will find 4-sessions on op-amp:

Here is also a short article that discusses the op-amp input protection using Schottky diodes protecting an op-amp.

https://www.ednasia.com/provide-robust-input-overvoltage-protection-for-amplifier-analog-input-modules/

Let us know if you have any questions,

Thank you and Regards,

Luis Chioye