With a small amount of additional circuitry, the INA199 series can be used in circuits subject to transients higher than 26 V, such as automotive applications. Use only Zener diode or Zener-type transient absorbers (sometimes referred to as transzorbs); any other type of transient absorber has an unacceptable time delay. Start by adding a pair of resistors (see Figure 7-5) as a working impedance for the Zener. Keeping these resistors as small as possible is preferable, most often approximately 10 Ω. Larger values can be used with an effect on gain as discussed in the Section 7.4.1 section. Because this circuit limits only short-term transients, many applications are satisfied with a 10-Ω resistor along with conventional Zener diodes of the lowest power rating that can be found. This combination uses the least amount of board space. These diodes can be found in packages as small as SOT-523 or SOD-523. See TIDA-00302 Transient Robustness for Current Shunt Monitor Design Guide, TIDU473 for more information on transient robustness and current-shunt monitor input protection.

Figure 7-5 INA199 Transient Protection Using Dual Zener Diodes

In the event that low-power zeners do not have sufficient transient absorption capability and a higher power transzorb must be used, the most package-efficient solution then involves using a single transzorb and back-to-back diodes between the device inputs. The most space-efficient solutions are dual series-connected diodes in a single SOT-523 or SOD-523 package. This method is shown in Figure 7-6. In either of these examples, the total board area required by the INA199 with all protective components is less than that of an SO-8 package, and only slightly greater than that of an MSOP-8 package.

Figure 7-6 INA199 Transient Protection Using a Single Transzorb and Input Clamps